Prospectus December 21, 2012 Institutional Classes. Premier Portfolio Premier Tax-Exempt Portfolio Premier U.S. Government Money Portfolio

Prospectus December 21, 2012 Institutional Classes Premier Portfolio Premier Tax-Exempt Portfolio Premier U.S. Government Money Portfolio

Prospectus December 21, 2012 Premier Portfolio Premier Tax-Exempt Portfolio Premier U.S. Government Money Portfolio Institutional Classes Premier Portfolio s investment objective is to provide current income consistent with preservation of capital and liquidity. Premier Tax-Exempt Portfolio s investment objective is to provide tax-exempt income consistent with preservation of capital and liquidity. Premier U.S. Government Money Portfolio s investment objective is a high level of current income consistent with the preservation of capital and the maintenance of liquidity. As with all other mutual fund securities, the Securities and Exchange Commission (SEC) has not approved or disapproved these securities or determined whether the information in this prospectus is adequate or accurate. Anyone who tells you otherwise is committing a crime. An investment in the Funds: m is not FDIC insured; m may lose value; and m is not guaranteed by a bank. There can be no assurance that each Fund will be able to maintain a stable net asset value of $1.00 per share.

Table of Contents Fund Summaries 1 Premier Portfolio 1 Premier Tax-Exempt Portfolio 3 Premier U.S. Government Money Portfolio 4 Investment Objective(s), Strategies, Risks and Portfolio Holdings 6 Premier Portfolio 6 Premier Tax-Exempt Portfolio 7 Premier U.S. Government Money Portfolio 9 Fund Management 10 The Adviser(s) 10 Adviser Compensation 10 Other Information 10 Dividends and Distributions 10 Financial Highlights 12 Hypothetical Investment and Expense Information 13 General Information A-1 Purchasing Shares A-1 Redeeming Shares A-1 Pricing of Shares A-2 Frequent Purchases and Redemptions of Fund Shares A-3 Exchange Policy A-3 Taxes A-3 Obtaining Additional Information Back Cover Invesco Treasurer s Series Trust

Fund Summaries PREMIER PORTFOLIO Investment Objective(s) The Fund s investment objective is to provide current income consistent with preservation of capital and liquidity. Fees and Expenses of the Fund This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Shareholder Fees (fees paid directly from your investment) Class: Institutional Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) None Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) None Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment) Class: Institutional Management Fees 0.25% Distribution and/or Service (12b-1) Fees None Other Expenses None Total Annual Fund Operating Expenses 0.25 Fee Waiver and/or Expense Reimbursement 1 0.07 Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement 0.18 1 Invesco Advisers, Inc. (Invesco or the Adviser) has contractually agreed, through at least December 31, 2013, to waive advisory fees equal to 0.07% of the average daily net assets of Premier Portfolio. Fee waivers have been restated to reflect this agreement. Unless the Board of Trustees and Invesco mutually agree to amend or continue the fee waiver agreement, it will terminate on December 31, 2013. Example. This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions, your costs would be: 1 Year 3 Years 5 Years 10 Years Institutional Class $18 $73 $134 $311 Principal Investment Strategies of the Fund The Fund invests primarily in high-quality U.S. dollar-denominated shortterm debt obligations, including: (i) securities issued by the U.S. Government or its agencies; (ii) bankers acceptances, certificates of deposit, and time deposits from U.S. and foreign banks; (iii) repurchase agreements; (iv) commercial paper; (v) municipal securities; and (vi) master notes. The Fund may engage in repurchase agreement transactions that are collateralized by cash or government securities. In addition, it may engage in repurchase agreement transactions that are collateralized by non government securities such as equity securities and securities that are rated investment grade and below investment grade by nationally recognized statistical rating organizations or unrated securities of comparable quality. The Fund will limit investments to those securities that are First Tier Securities (defined below) at the time of purchase. The Fund is a money market fund that seeks to maintain a stable price of $1.00 per share by using the amortized cost method to value portfolio securities and rounding the share value to the nearest cent. The Fund invests in conformity with the Security and Exchange Commission (SEC) rules and regulation requirements for money market funds for the quality, maturity, diversification and liquidity of investments. The Fund invests only in U.S. dollar-denominated securities maturing within 397 days of the date of purchase, with certain exceptions permitted by applicable regulations. The Fund maintains a dollar-weighted average portfolio maturity of no more than 60 days, and a dollar-weighted average portfolio maturity as determined without exceptions regarding certain interest rate adjustments under Rule 2a-7 under the Investment Company Act of 1940 of no more than 120 days. Each investment must be determined to present minimal credit risks by the Fund s Adviser pursuant to guidelines approved by the Fund s Board of Trustees, and must be an Eligible Security as defined under applicable regulations. First Tier Securities generally means Eligible Securities rated within the highest short-term rating category, an unrated security of comparable quality as determined by the Adviser under the supervision of the Board of Trustees, U.S. Government Securities as defined by applicable regulations, and securities issued by other registered money market funds. The Fund invests from time to time in U.S. dollar-denominated foreign securities. The Fund may also invest in securities, whether or not considered foreign securities, which carry foreign credit exposure. In selecting securities for the Fund s portfolio, the portfolio managers focus on securities that offer safety, liquidity, and a competitive yield. The Adviser conducts a credit analysis of each potential issuer prior to the purchase of its securities. The portfolio managers normally hold portfolio securities to maturity, but may sell a security when they deem it advisable, such as when market or credit factors materially change. Principal Risks of Investing in the Fund As with any mutual fund investment, loss of money is a risk of investing. An investment in the Fund is not a deposit in a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency. Although the Fund seeks to preserve the value of your investment at $1.00 per share, you may lose money by investing in the Fund. The risks associated with an investment in the Fund can increase during times of significant market volatility. The principal risks of investing in the Fund are: Cash/Cash Equivalents Risk. Holding cash or cash equivalents may negatively affect performance. Counterparty Risk. Counterparty risk is the risk that the other party to the contract will not fulfill its contractual obligations, which may cause losses or additional costs to the Fund. Credit Risk. The issuer of instruments in which the Fund invests may be unable to meet interest and/or principal payments, thereby causing its instruments to decrease in value and lowering the issuer s credit rating. Foreign Credit Exposure Risk. U.S. dollar-denominated securities carrying foreign credit exposure may be affected by unfavorable political, economic or governmental developments that could affect payments of principal and interest. Foreign Securities Risk. The value of the Fund s foreign investments may be adversely affected by political and social instability, changes in economic or taxation policies, difficulties when enforcing obligations, decreased liquidity, and increased volatility. Foreign companies may be 1 Invesco Treasurer s Series Trust

subject to less regulation resulting in less publicly available information about the companies. Industry Focus Risk. To the extent the Fund invests in securities issued or guaranteed by companies in the banking and financial services industries, the Fund s performance will depend on the overall condition of those industries, which may be affected by the following factors: the supply of short-term financing, changes in government regulation and interest rates, and the overall economy. Interest Rate Risk. Interest rate risk refers to the risk that bond prices generally fall as interest rates rise; conversely, bond prices generally rise as interest rates fall. Specific bonds differ in their sensitivity to changes in interest rates depending on their individual characteristics, including duration. Liquidity Risk. The Fund may hold illiquid securities that it may be unable to sell at the preferred time or price and could lose its entire investment in such securities. Management Risk. The investment techniques and risk analysis used by the Fund s portfolio managers may not produce the desired results. Market Risk. The prices of and the income generated by the Fund s securities may decline in response to, among other things, investor sentiment, general economic and market conditions, regional or global instability, and interest rate fluctuations. Money Market Fund Risk. Although the Fund seeks to preserve the value of your investment at $1.00 per share, you may lose money by investing in the Fund. The share price of money market funds can fall below the $1.00 share price. You should not rely on or expect the Fund s adviser or its affiliates to enter into support agreements or take other actions to maintain the Fund s $1.00 share price. The credit quality of the Fund s holdings can change rapidly in certain markets, and the default of a single holding could have an adverse impact on the Fund s share price. The Fund s share price can also be negatively affected during periods of high redemption pressures and/or illiquid markets. Further regulation could impact the way the Fund is managed, possibly negatively impacting its return. Additionally, the Fund s yield will vary as the short-term securities in its portfolio mature or are sold and the proceeds are reinvested in other securities. Municipal Securities Risk. The Fund may invest in municipal securities. Constitutional amendments, legislative enactments, executive orders, administrative regulations, voter initiatives, and the issuer s regional economic conditions may affect the municipal security s value, interest payments, repayment of principal and the Fund s ability to sell it. Failure of a municipal security issuer to comply with applicable tax requirements may make income paid thereon taxable, resulting in a decline in the security s value. In addition, there could be changes in applicable tax laws or tax treatments that reduce or eliminate the current federal income tax exemption on municipal securities or otherwise adversely affect the current federal or state tax status of municipal securities. Reinvestment Risk. Reinvestment risk is the risk that a bond s cash flows (coupon income and principal repayment) will be reinvested at an interest rate below that on the original bond. Repurchase Agreement Risk. If the seller of a repurchase agreement defaults or otherwise does not fulfill its obligations, the Fund may incur delays and losses arising from selling the underlying securities, enforcing its rights, or declining collateral value. These risks are magnified to the extent that a repurchase agreement is secured by securities other than cash or U.S. Government securities. U.S. Government Obligations Risk. The Fund may invest in obligations issued by U.S. Government agencies and instrumentalities that may receive varying levels of support from the government, which could affect the Fund s ability to recover should they default. Variable-Rate Demand Notes Risk. The absence of an active secondary market for certain variable and floating rate notes could make it difficult to dispose of the instruments, and a portfolio could suffer a loss if the issuer defaults during periods in which a portfolio is not entitled to exercise its demand rights. Performance Information The bar chart and performance table provide an indication of the risks of investing in the Fund. The bar chart shows changes in the performance of the Fund from year to year as of December 31. The Fund s past performance (before and after taxes) is not necessarily an indication of its future performance. Updated performance information is available on the Fund s website at www.invesco.com/us. Annual Total Returns 6% 5% 4% 3% 2% 1% 0% 06 07 08 09 10 11 5.04% 5.27% 2.89% 0.46% 0.09% 0.07% Institutional Class year-to-date (ended September 30, 2012): 0.09% Best Quarter (ended September 30, 2007): 1.33% Worst Quarter (ended March 31, 2010 and September 30, 2011): 0.01% Average Annual Total Returns (for the periods ended December 31, 2011) 1 Year 5 Years Since Inception Institutional Class: Inception (2/25/2005) 0.07% 1.74% 2.41% Management of the Fund Investment Adviser: Invesco Advisers, Inc. Purchase and Sale of Fund Shares You may purchase or redeem shares of a Fund on any business day the Fund is open through your financial intermediary, by telephone at (800) 659-1005, or through Liquidity LINK, or if you are investing directly, by sending your completed account application and purchase amount to Invesco Investment Services, Inc., P.O. Box 219286, Kansas City, MO 94121-9286. The minimum investments for Institutional Class fund accounts are as follows: Initial Investments Per Fund Account* $1 Million Additional Investments Per Fund Account No minimum * An intermediary may aggregate its master accounts and subaccounts to satisfy the minimum investment requirement. Tax Information The Fund s distributions generally are taxable to you as ordinary income, unless you are investing through a tax-deferred arrangement, such as a 401(k) plan or individual retirement account. Payments to Broker-Dealers and Other Financial Intermediaries If you purchase the Fund through a broker-dealer or other financial intermediary (such as a bank), the Fund and the Fund s distributor or its related companies may pay the intermediary for the sale of Fund shares and related services. These payments may create a conflict of interest by influencing the broker-dealer or other intermediary and your salesperson or financial adviser to recommend the Fund over another investment. Ask your salesperson or financial adviser or visit your financial intermediary s Web site for more information. 2 Invesco Treasurer s Series Trust

PREMIER TAX-EXEMPT PORTFOLIO Investment Objective(s) The Fund s investment objective is to provide tax-exempt income consistent with preservation of capital and liquidity. Fees and Expenses of the Fund This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Shareholder Fees (fees paid directly from your investment) Class: Institutional Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) None Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) None Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment) Class: Institutional Management Fees 0.25% Distribution and/or Service (12b-1) Fees None Other Expenses None Total Annual Fund Operating Expenses 0.25 Example. This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions, your costs would be: 1 Year 3 Years 5 Years 10 Years Institutional Class $26 $80 $141 $318 Principal Investment Strategies of the Fund The Fund invests under normal circumstances at least 80% of its net assets (plus any borrowings for investment purposes) in securities that (1) pay interest that is excluded from gross income for federal income tax purposes, and (2) do not produce income that will be considered to be an item of preference for purposes of the alternative minimum tax. The Fund will limit investments to those securities that are First Tier Securities (defined below) at the time of purchase. The Fund invests only in high-quality U.S. dollar-denominated shortterm debt obligations, including: (i) municipal securities; (ii) tax-exempt commercial paper; and (iii) cash equivalents. These securities may have credit and liquidity enhancements provided by banks, insurance companies or other financial institutions. Municipal securities include debt obligations of states, territories and possessions of the United States and the District of Columbia, their political subdivisions, agencies, instrumentalities, authorities thereof, and multi-state agencies, issued to obtain funds for various public purposes. Municipal lease obligations, synthetic municipal securities and certain types of industrial revenue bonds are treated as municipal securities. Other securities held by the fund may be structured with demand features which have the effect of shortening the security s maturity. The Fund is a money market fund that seeks to maintain a stable price of $1.00 per share by using the amortized cost method to value portfolio securities and rounding the share value to the nearest cent. The Fund invests in conformity with SEC rules and regulation requirements for money market funds for the quality, maturity, diversification and liquidity of investments. The Fund invests only in U.S. dollar-denominated securities maturing within 397 days of the date of purchase, with certain exceptions permitted by applicable regulations. The Fund maintains a dollar-weighted average portfolio maturity of no more than 60 days, and a dollar-weighted average portfolio maturity as determined without exceptions regarding certain interest rate adjustments under Rule 2a-7 under the Investment Company Act of 1940 of no more than 120 days. Each investment must be determined to present minimal credit risks by the Fund s Adviser pursuant to guidelines approved by the Fund s Board of Trustees, and must be an Eligible Security as defined under applicable regulations. First Tier Securities generally means Eligible Securities rated within the highest short-term rating category, an unrated security of comparable quality as determined by the Adviser under the supervision of the Board of Trustees, U.S. Government Securities as defined by applicable regulations, and securities issued by other registered money market funds. The Fund may invest up to 20% of its total assets in money market instruments that may be subject to federal taxes, including Treasury securities, repurchase agreements, bankers acceptances, commercial paper, U.S. dollar-denominated foreign securities and master notes. The Fund may also invest in securities, whether or not considered foreign securities, which carry foreign credit exposure. In selecting securities for the Fund s portfolio, the portfolio managers focus on securities that offer safety, liquidity, and a competitive yield. The Adviser conducts a credit analysis of each potential issuer prior to the purchase of its securities. The portfolio structure is driven to some extent by the supply and availability of municipal obligations. The portfolio managers manage liquidity, for instance, by trading in daily and weekly variable-rate demand notes. The portfolio managers normally hold portfolio securities to maturity, but may sell a security when they deem it advisable, such as when market or credit factors materially change. Principal Risks of Investing in the Fund As with any mutual fund investment, loss of money is a risk of investing. An investment in the Fund is not a deposit in a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency. Although the Fund seeks to preserve the value of your investment at $1.00 per share, you may lose money by investing in the Fund. The risks associated with an investment in the Fund can increase during times of significant market volatility. The principal risks of investing in the Fund are: Cash/Cash Equivalents Risk. Holding cash or cash equivalents may negatively affect performance. Counterparty Risk. Counterparty risk is the risk that the other party to the contract will not fulfill its contractual obligations, which may cause losses or additional costs to the Fund. Credit Risk. The issuer of instruments in which the Fund invests may be unable to meet interest and/or principal payments, thereby causing its instruments to decrease in value and lowering the issuer s credit rating. Foreign Credit Exposure Risk. U.S. dollar-denominated securities carrying foreign credit exposure may be affected by unfavorable political, economic or governmental developments that could affect payments of principal and interest. Foreign Securities Risk. The value of the Fund s foreign investments may be adversely affected by political and social instability, changes in economic or taxation policies, difficulties when enforcing obligations, decreased liquidity, and increased volatility. Foreign companies may be subject to less regulation resulting in less publicly available information about the companies. Industry Focus Risk. To the extent the Fund invests in securities issued or guaranteed by companies in the banking and financial services industries, the Fund s performance will depend on the overall condition of those industries, which may be affected by the following factors: the 3 Invesco Treasurer s Series Trust

supply of short-term financing, changes in government regulation and interest rates, and the overall economy. Interest Rate Risk. Interest rate risk refers to the risk that bond prices generally fall as interest rates rise; conversely, bond prices generally rise as interest rates fall. Specific bonds differ in their sensitivity to changes in interest rates depending on their individual characteristics, including duration. Liquidity Risk. The Fund may hold illiquid securities that it may be unable to sell at the preferred time or price and could lose its entire investment in such securities. Management Risk. The investment techniques and risk analysis used by the Fund s portfolio managers may not produce the desired results. Market Risk. The prices of and the income generated by the Fund s securities may decline in response to, among other things, investor sentiment, general economic and market conditions, regional or global instability, and interest rate fluctuations. Money Market Fund Risk. Although the Fund seeks to preserve the value of your investment at $1.00 per share, you may lose money by investing in the Fund. The share price of money market funds can fall below the $1.00 share price. You should not rely on or expect the Fund s adviser or its affiliates to enter into support agreements or take other actions to maintain the Fund s $1.00 share price. The credit quality of the Fund s holdings can change rapidly in certain markets, and the default of a single holding could have an adverse impact on the Fund s share price. The Fund s share price can also be negatively affected during periods of high redemption pressures and/or illiquid markets. Further regulation could impact the way the Fund is managed, possibly negatively impacting its return. Additionally, the Fund s yield will vary as the short-term securities in its portfolio mature or are sold and the proceeds are reinvested in other securities. Municipal Securities Risk. The Fund may invest in municipal securities. Constitutional amendments, legislative enactments, executive orders, administrative regulations, voter initiatives, and the issuer s regional economic conditions may affect the municipal security s value, interest payments, repayment of principal and the Fund s ability to sell it. Failure of a municipal security issuer to comply with applicable tax requirements may make income paid thereon taxable, resulting in a decline in the security s value. In addition, there could be changes in applicable tax laws or tax treatments that reduce or eliminate the current federal income tax exemption on municipal securities or otherwise adversely affect the current federal or state tax status of municipal securities. Reinvestment Risk. Reinvestment risk is the risk that a bond s cash flows (coupon income and principal repayment) will be reinvested at an interest rate below that on the original bond. Variable-Rate Demand Notes Risk. The absence of an active secondary market for certain variable and floating rate notes could make it difficult to dispose of the instruments, and a portfolio could suffer a loss if the issuer defaults during periods in which a portfolio is not entitled to exercise its demand rights. Performance Information The bar chart and performance table provide an indication of the risks of investing in the Fund. The bar chart shows changes in the performance of the Fund from year to year as of December 31. The Fund s past performance (before and after taxes) is not necessarily an indication of its future performance. Updated performance information is available on the Fund s website at www.invesco.com/us. Annual Total Returns 4.0% 3.5% 3.0% 2.5% 2.0% 1.5% 1.0% 0.5% 0.0% 06 07 08 09 10 11 3.32% 3.51% 2.33% 0.41% 0.11% 0.05% Institutional Class year-to-date (ended September 30, 2012): 0.02% Best Quarter (ended June 30, 2007 and September 30, 2007): 0.89% Worst Quarter (ended December 31, 2011): 0.00% Average Annual Total Returns (for the periods ended December 31, 2011) 1 Year 5 Years Since Inception Institutional Class: Inception (2/25/2005) 0.05% 1.27% 1.71% Management of the Fund Investment Adviser: Invesco Advisers, Inc. Purchase and Sale of Fund Shares You may purchase or redeem shares of a Fund on any business day the Fund is open through your financial intermediary, by telephone at (800) 659-1005, or through Liquidity LINK, or if you are investing directly, by sending your completed account application and purchase amount to Invesco Investment Services, Inc., P.O. Box 219286, Kansas City, MO 94121-9286. The minimum investments for Institutional Class fund accounts are as follows: Initial Investments Per Fund Account* $1 Million Additional Investments Per Fund Account No minimum * An intermediary may aggregate its master accounts and subaccounts to satisfy the minimum investment requirement. Tax Information The Fund s distributions primarily are exempt from regular federal income tax. A portion of these distributions, however, may be subject to the federal alternative minimum tax and state and local taxes. The Fund may also make distributions that are taxable to you as ordinary income. Payments to Broker-Dealers and Other Financial Intermediaries If you purchase the Fund through a broker-dealer or other financial intermediary (such as a bank), the Fund and the Fund s distributor or its related companies may pay the intermediary for the sale of Fund shares and related services. These payments may create a conflict of interest by influencing the broker-dealer or other intermediary and your salesperson or financial adviser to recommend the Fund over another investment. Ask your salesperson or financial adviser or visit your financial intermediary s Web site for more information. PREMIER U.S. GOVERNMENT MONEY PORTFOLIO Investment Objective(s) The Fund s investment objective is a high level of current income consistent with the preservation of capital and the maintenance of liquidity. 4 Invesco Treasurer s Series Trust

Fees and Expenses of the Fund This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Shareholder Fees (fees paid directly from your investment) Class: Institutional Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) None Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) None Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment) Class: Institutional Management Fees 0.25% Distribution and/or Service (12b-1) Fees None Other Expenses None Total Annual Fund Operating Expenses 0.25 Fee Waiver and/or Expense Reimbursement 1 0.07 Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement 0.18 1 Invesco Advisers, Inc. (Invesco or the Adviser) has contractually agreed, through at least December 31, 2013, to waive advisory fees equal to 0.07% of the average daily net assets of Premier U.S. Government Money Portfolio. Fee waivers have been restated to reflect this agreement. Unless the Board of Trustees and Invesco mutually agree to amend or continue the fee waiver agreement, it will terminate on December 31, 2013. Example. This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions, your costs would be: 1 Year 3 Years 5 Years 10 Years Institutional Class $18 $73 $134 $311 Principal Investment Strategies of the Fund The Fund invests under normal circumstances at least 80% of its net assets (plus any borrowings for investment purposes) in (i) direct obligations of the U.S. Treasury, (ii) other securities issued or guaranteed as to principal and interest by the U.S. government or its agencies and instrumentalities (Agency Securities), and (iii) repurchase agreements secured by those obligations referenced in (i) and (ii) above. Agency Securities may be supported by (i) the full faith and credit of the U.S. Treasury; (ii) the right of the issuer to borrow from the U.S. Treasury; (iii) the discretionary authority of the U.S. government to purchase certain obligations of the agency or instrumentality; or (iv) the credit of the agency or instrumentality. At the present time, the fund has no current intention to invest in securities other than direct obligations of the U.S. Treasury, Agency Securities, and repurchase agreements secured by such obligations. The Fund will limit investments to those securities that are First Tier Securities (defined below) at the time of purchase. The Fund is a money market fund that seeks to maintain a stable price of $1.00 per share by using the amortized cost method to value portfolio securities and rounding the share value to the nearest cent. The Fund invests in conformity with SEC rules and regulation requirements for money market funds for the quality, maturity, diversification and liquidity of investments. The Fund invests only in U.S. dollar-denominated securities maturing within 397 days of the date of purchase, with certain exceptions permitted by applicable regulations. The Fund maintains a dollar-weighted average portfolio maturity of no more than 60 days, and a dollar-weighted average portfolio maturity as determined without exceptions regarding certain interest rate adjustments under Rule 2a-7 under the Investment Company Act of 1940 of no more than 120 days. Each investment must be determined to present minimal credit risks by the Fund s Adviser pursuant to guidelines approved by the Fund s Board of Trustees, and must be an Eligible Security as defined under applicable regulations. First Tier Securities generally means Eligible Securities rated within the highest short-term rating category, an unrated security of comparable quality as determined by the Adviser under the supervision of the Board of Trustees, U.S. Government Securities as defined by applicable regulations, and securities issued by other registered money market funds. In selecting securities for the Fund s portfolio, the portfolio managers focus on securities that offer safety, liquidity, and a competitive yield. The Adviser conducts a credit analysis of each potential issuer prior to the purchase of its securities. The portfolio managers normally hold portfolio securities to maturity, but may sell a security when they deem it advisable, such as when market or credit factors materially change. Principal Risks of Investing in the Fund As with any mutual fund investment, loss of money is a risk of investing. An investment in the Fund is not a deposit in a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency. Although the Fund seeks to preserve the value of your investment at $1.00 per share, you may lose money by investing in the Fund. The risks associated with an investment in the Fund can increase during times of significant market volatility. The principal risks of investing in the Fund are: Cash/Cash Equivalents Risk. Holding cash or cash equivalents may negatively affect performance. Interest Rate Risk. Interest rate risk refers to the risk that bond prices generally fall as interest rates rise; conversely, bond prices generally rise as interest rates fall. Specific bonds differ in their sensitivity to changes in interest rates depending on their individual characteristics, including duration. Liquidity Risk. The Fund may hold illiquid securities that it may be unable to sell at the preferred time or price and could lose its entire investment in such securities. Management Risk. The investment techniques and risk analysis used by the Fund s portfolio managers may not produce the desired results. Market Risk. The prices of and the income generated by the Fund s securities may decline in response to, among other things, investor sentiment, general economic and market conditions, regional or global instability, and interest rate fluctuations. Money Market Fund Risk. Although the Fund seeks to preserve the value of your investment at $1.00 per share, you may lose money by investing in the Fund. The share price of money market funds can fall below the $1.00 share price. You should not rely on or expect the Fund s adviser or its affiliates to enter into support agreements or take other actions to maintain the Fund s $1.00 share price. The credit quality of the Fund s holdings can change rapidly in certain markets, and the default of a single holding could have an adverse impact on the Fund s share price. The Fund s share price can also be negatively affected during periods of high redemption pressures and/or illiquid markets. Further regulation could impact the way the Fund is managed, possibly negatively impacting its return. Additionally, the Fund s yield will vary as the short-term securities in its portfolio mature or are sold and the proceeds are reinvested in other securities. Reinvestment Risk. Reinvestment risk is the risk that a bond s cash flows (coupon income and principal repayment) will be reinvested at an interest rate below that on the original bond. 5 Invesco Treasurer s Series Trust

Repurchase Agreement Risk. If the seller of a repurchase agreement defaults or otherwise does not fulfill its obligations, the Fund may incur delays and losses arising from selling the underlying securities, enforcing its rights, or declining collateral value. U.S. Government Obligations Risk. The Fund may invest in obligations issued by U.S. Government agencies and instrumentalities that may receive varying levels of support from the government, which could affect the Fund s ability to recover should they default. Performance Information The bar chart and performance table provide an indication of the risks of investing in the Fund. The bar chart shows changes in the performance of the Fund from year to year as of December 31. The Fund s past performance (before and after taxes) is not necessarily an indication of its future performance. Updated performance information is available on the Fund s website at www.invesco.com/us. Annual Total Returns 6% 5% 4% 3% 2% 1% 0% 07 08 09 10 11 5.09% 2.29% 0.28% 0.03% 0.02% Institutional Class year-to-date (ended September 30, 2012): 0.02% Best Quarter (ended September 30, 2007): 1.29% Worst Quarter (ended June 30, 2011 through December 31, 2011): 0.00% Average Annual Total Returns (for the periods ended December 31, 2011) 1 Year 5 Years Since Inception Institutional Class: Inception (6/28/2006) 0.02% 1.52% 1.86% Management of the Fund Investment Adviser: Invesco Advisers, Inc. Purchase and Sale of Fund Shares You may purchase or redeem shares of a Fund on any business day the Fund is open through your financial intermediary, by telephone at (800) 659-1005, or through Liquidity LINK, or if you are investing directly, by sending your completed account application and purchase amount to Invesco Investment Services, Inc., P.O. Box 219286, Kansas City, MO 94121-9286. The minimum investments for Institutional Class fund accounts are as follows: Initial Investments Per Fund Account* $1 Million Additional Investments Per Fund Account No minimum * An intermediary may aggregate its master accounts and subaccounts to satisfy the minimum investment requirement. Tax Information The Fund s distributions generally are taxable to you as ordinary income, unless you are investing through a tax-deferred arrangement, such as a 401(k) plan or individual retirement account. Payments to Broker-Dealers and Other Financial Intermediaries If you purchase the Fund through a broker-dealer or other financial intermediary (such as a bank), the Fund and the Fund s distributor or its related companies may pay the intermediary for the sale of Fund shares and related services. These payments may create a conflict of interest by influencing the broker-dealer or other intermediary and your salesperson or financial adviser to recommend the Fund over another investment. Ask your salesperson or financial adviser or visit your financial intermediary s Web site for more information. Investment Objective(s), Strategies, Risks and Portfolio Holdings Premier Portfolio Objective(s) and Strategies The Fund s investment objective is to provide current income consistent with preservation of capital and liquidity. The Fund s investment objective may be changed by the Board of Trustees without shareholder approval. The Fund invests primarily in high-quality U.S. dollar-denominated short-term debt obligations, including: (i) securities issued by the U.S. Government or its agencies; (ii) bankers acceptances, certificates of deposit, and time deposits from U.S. and foreign banks; (iii) repurchase agreements; (iv) commercial paper; (v) municipal securities; and (vi) master notes. The Fund may engage in repurchase agreement transactions that are collateralized by cash or government securities. In addition, it may engage in repurchase agreement transactions that are collateralized by non government securities such as equity securities and securities that are rated investment grade and below investment grade by nationally recognized statistical rating organizations or unrated securities of comparable quality. The Fund will limit investments to those securities that are First Tier Securities (defined below) at the time of purchase. As permitted by Rule 2a-7 under the Investment Company Act of 1940 (Rule 2a-7), the Fund seeks to maintain a stable price of $1.00 per share by using the amortized cost method to value portfolio securities and rounding the share value to the nearest cent. The Fund invests in conformity with SEC rules and regulation requirements for money market funds for the quality, maturity, diversification and liquidity of investments. The Fund invests only in U.S. dollar-denominated securities maturing within 397 days of the date of purchase, with certain exceptions permitted by applicable regulations. The Fund maintains a dollar-weighted average portfolio maturity of no more than 60 days, and a dollar-weighted average portfolio maturity as determined without exceptions regarding certain interest rate adjustments under Rule 2a-7 under the Investment Company Act of 1940 of no more than 120 days. Each investment must be determined to present minimal credit risks by the Fund s Adviser pursuant to guidelines approved by the Fund s Board of Trustees, and must be an Eligible Security as defined under applicable regulations. First Tier Securities generally means Eligible Securities rated within the highest shortterm rating category, an unrated security of comparable quality as determined by the Adviser under the supervision of the Board of Trustees, U.S. Government Securities as defined by applicable regulations, and securities issued by other registered money market funds. The Fund invests from time to time in U.S. dollar-denominated foreign securities. The Fund may also invest in securities, whether or not considered foreign securities, which carry foreign credit exposure. In selecting securities for the Fund s portfolio, the portfolio managers focus on securities that offer safety, liquidity, and a competitive yield. The Adviser conducts a credit analysis of each potential issuer prior to the purchase of its securities. The portfolio managers normally hold portfolio securities to maturity, but may sell a security when they deem it advisable, such as when market or credit factors materially change. The Fund may, from time to time, take temporary defensive positions by holding cash, shortening the Fund s dollar-weighted average maturity or investing in other securities that are eligible securities for purchase by money market funds as described in this prospectus and the Fund s Statement of Additional Information (SAI) and that are consistent with the 6 Invesco Treasurer s Series Trust

Fund s principal investment strategies, in anticipation of, or in response to, adverse market, economic, political or other conditions. It is possible that such investments could affect the Fund s returns. The Fund s investments in the types of securities described in this prospectus vary from time to time, and, at any time, the Fund may not be invested in all of the types of securities described in this prospectus. Any percentage limitations with respect to assets of the Fund are applied at the time of purchase. Risks The principal risks of investing in the Fund are: Cash/Cash Equivalents Risk. To the extent the Fund holds cash or cash equivalents rather than securities in which it primarily invests or uses to manage risk, the Fund may not achieve its investment objectives and may underperform. Counterparty Risk. Counterparty risk is the risk that the other party to the contract will not fulfill its contractual obligations, which may cause losses or additional costs to the Fund. Credit Risk. The issuers of instruments in which the Fund invests may be unable to meet interest and/or principal payments. An issuer s securities may decrease in value if its financial strength weakens, which may reduce its credit rating and possibly its ability to meet its contractual obligations. Foreign Credit Exposure Risk. U.S. dollar denominated securities carrying foreign credit exposure may be affected by unfavorable political, economic or governmental developments that could affect payments of principal and interest. Foreign Securities Risk. The value of the Fund s foreign investments may be adversely affected by political and social instability in their home countries, by changes in economic or taxation policies in those countries, or by the difficulty in enforcing obligations in those countries. Foreign companies generally may be subject to less stringent regulations than U.S. companies, including financial reporting requirements and auditing and accounting controls. As a result, there generally is less publicly available information about foreign companies than about U.S. companies. Trading in many foreign securities may be less liquid and more volatile than U.S. securities due to the size of the market or other factors. Industry Focus Risk. To the extent the Fund invests in securities issued or guaranteed by companies in the banking and financial services industries, the Fund s performance will depend on the overall condition of those industries. Financial services companies are highly dependent on the supply of short-term financing. The value of securities of issuers in the banking and financial services industry can be sensitive to changes in government regulation and interest rates and to economic downturns in the United States and abroad. Interest Rate Risk. Interest rate risk refers to the risk that bond prices generally fall as interest rates rise; conversely, bond prices generally rise as interest rates fall. Specific bonds differ in their sensitivity to changes in interest rates depending on their individual characteristics. One measure of this sensitivity is called duration. The longer the duration of a particular bond, the greater its price sensitivity is to interest rates. Similarly, a longer duration portfolio of securities has greater price sensitivity. Falling interest rates may also prompt some issuers to refinance existing debt, which could affect the Fund s performance. Liquidity Risk. A security is considered to be illiquid if the Fund is unable to sell such security at approximately the value the Fund ascribes to it within seven calendar days. A security may be deemed illiquid due to a lack of trading volume in the security or if the security is privately placed and not traded in any public market or is otherwise restricted from trading. The Fund may be unable to sell illiquid securities at the time or price it desires and could lose its entire investment in such securities. Further, certain restricted securities require special registration, liabilities and costs, and could pose valuation difficulties. Management Risk. The investment techniques and risk analysis used by the Fund s portfolio managers may not produce the desired results. Market Risk. The prices of and the income generated by the Fund s securities may decline in response to, among other things, investor sentiment, general economic and market conditions, regional or global instability, and interest rate fluctuations. Money Market Fund Risk. Although the Fund seeks to preserve the value of your investment at $1.00 per share, you may lose money by investing in the Fund. The share price of money market funds can fall below the $1.00 share price. You should not rely on or expect the Fund s adviser or its affiliates to enter into support agreements or take other actions to maintain the Fund s $1.00 share price. The credit quality of the Fund s holdings can change rapidly in certain markets, and the default of a single holding could have an adverse impact on the Fund s share price. The Fund s share price can also be negatively affected during periods of high redemption pressures and/or illiquid markets. Further regulation could impact the way the Fund is managed, possibly negatively impacting its return. Additionally, the Fund s yield will vary as the short-term securities in its portfolio mature or are sold and the proceeds are reinvested in other securities. Municipal Securities Risk. The Fund may invest in municipal securities. Constitutional amendments, legislative enactments, executive orders, administrative regulations, voter initiatives, and the issuer s regional economic conditions may affect the municipal security s value, interest payments, repayment of principal and the Fund s ability to sell it. Revenue bonds are generally not backed by the taxing power of the issuing municipality. To the extent that a municipal security is not heavily followed by the investment community or such security issue is relatively small, the security may be difficult to value or sell at a desirable price. If the Internal Revenue Service determines that an issuer of a municipal security has not complied with applicable tax requirements, interest from the security could be treated as taxable, which could result in a decline in the security s value. In addition, there could be changes in applicable tax laws or tax treatments that reduce or eliminate the current federal income tax exemption on municipal securities or otherwise adversely affect the current federal or state tax status of municipal securities. Reinvestment Risk. Reinvestment risk is the risk that a bond s cash flows (coupon income and principal repayment) will be reinvested at an interest rate below that on the original bond. If interest rates decline, the underlying bond may rise in value, but the cash flows received from that bond may have to be reinvested at a lower interest rate. Repurchase Agreement Risk. If the seller of a repurchase agreement defaults or otherwise does not fulfill its obligations, the Fund may incur delays and losses arising from selling the underlying securities, enforcing its rights, or declining collateral value. These risks are magnified to the extent that a repurchase agreement is secured by securities other than cash or U.S. Government securities. U.S. Government Obligations Risk. The Fund may invest in obligations issued by U.S. Government agencies and instrumentalities that may receive varying levels of support from the government, which could affect the Fund s ability to recover should they default. Variable-Rate Demand Notes Risk. The absence of an active secondary market for certain variable and floating rate notes could make it difficult to dispose of the instruments, and a portfolio could suffer a loss if the issuer defaults during periods in which a portfolio is not entitled to exercise its demand rights. Premier Tax-Exempt Portfolio Objective(s) and Strategies The Fund s investment objective is to provide tax-exempt income consistent with preservation of capital and liquidity. The Fund s investment objective may be changed by the Board of Trustees without shareholder approval. The Fund invests under normal circumstances at least 80% of its net assets (plus any borrowings for investment purposes) in securities that (1) pay interest that is excluded from gross income for federal income tax 7 Invesco Treasurer s Series Trust