Strategy. Under normal circumstances, the Fund will invest at least 80% of the value of its net assets (plus any borrowings for investment purposes) in investments the income from which is exempt from federal income tax under regular tax rules. The policy stated in the foregoing sentence is a fundamental policy of the Fund and may not be changed without shareholder approval of a majority of the Funds outstanding voting securities, as defined in the Investment Company Act of 1940, as amended (1940 Act). The Fund invests, under normal circumstances, at least 80% of its net assets (plus any borrowings for investment purposes) in municipal debt securities that (1) pay interest that is excluded from gross income for federal income tax … Show more… Under normal circumstances, the Fund will invest at least 80% of the value of its net assets (plus any borrowings for investment purposes) in investments the income from which is exempt from federal income tax under regular tax rules. The policy stated in the foregoing sentence is a fundamental policy of the Fund and may not be changed without shareholder approval of a majority of the Funds outstanding voting securities, as defined in the Investment Company Act of 1940, as amended (1940 Act). The Fund invests, under normal circumstances, at least 80% of its net assets (plus any borrowings for investment purposes) in municipal debt 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. In complying with this 80% investment requirement, the Fund may invest in derivatives and other instruments that have economic characteristics similar to the Funds direct investments that are counted toward the 80% investment requirement. At least 80% of the Funds net assets will normally be invested in investment grade municipal debt securities. Investment grade securities are: (i) securities rated BBB- or higher by S&P Global Ratings (S&P) or Baa3 or higher by Moodys Investors Service, Inc. (Moodys) or an equivalent rating by another nationally recognized statistical rating organization (NRSRO), (ii) securities with comparable short-term NRSRO ratings, or (iii) unrated securities determined by Invesco Advisers, Inc. (Invesco or the Adviser) to be of comparable quality, each at the time of purchase. If two or more NRSROs have assigned different ratings to a security, the Adviser uses the highest rating assigned. At the present time, the Fund will not invest in municipal debt securities if the interest on such securities is subject to the federal alternative minimum tax. Municipal securities include debt obligations of states, territories or possessions of the United States and the District of Columbia and their political subdivisions, agencies and instrumentalities, the interest on which is exempt from federal income tax, at the time of issuance, in the opinion of bond counsel or other counsel to the issuers of such securities. The principal types of municipal debt securities purchased by the Fund are revenue obligations and general obligations. To meet its investment objective, the Fund invests in different types of general obligation and revenue obligation securities, including fixed and variable rate securities, municipal notes, variable rate demand notes, municipal leases, custodial receipts, and participation certificates. The Fund may also invest in other types of municipal securities. Under normal market conditions, the Fund invests primarily in municipal securities classified as revenue bonds. Up to 20% of the Funds net assets may be invested in municipal debt securities that are determined to be below-investment-grade quality. This restriction is applied at the time of purchase and the Fund may continue to hold a security whose credit rating has been downgraded or, in the case of an unrated security, after the Funds Adviser, Invesco Adviser, Inc. (Invesco or the Adviser) has changed its assessment of the securitys credit quality. As a result, credit rating downgrades or other market fluctuations may cause the Funds holdings of below-investment-grade securities to exceed, at times significantly, this restriction for an extended period of time. These types of securities are commonly referred to as junk bonds. With respect to such investments, the Fund has not established any limit on the percentage of its portfolio that may be invested in securities in any one rating category. The Fund may invest more than 25% of its net assets in a segment of the municipal securities market with similar characteristics if the Adviser determines that the yields available from obligations in a particular segment justify the additional risks of a larger investment in such segment. The Fund may not, however, invest more than 25% of its net assets in industrial development revenue bonds issued for companies in the same industry. The Fund may invest in illiquid or thinly traded investments. The Fund may also invest in securities that are subject to resale restrictions and/or exempt from registration under the Securities Act of 1933, as amended (Securities Act), such as those contained in Rule 144A promulgated under the Securities Act. The Funds investments may include securities that do not produce immediate cash income, such as zero coupon securities and payment-in-kind securities. The Fund may purchase and sell securities on a when-issued and delayed delivery basis, which means that the Fund may buy or sell a security with payment and delivery taking place in the future. The Fund can invest in inverse floating rate interests (Inverse Floaters) issued in connection with municipal tender option bond (TOB) financing transactions to generate leverage for the Fund. The Funds investments in Inverse Floaters are included for purposes of the 80% policy described above. The Fund can invest in derivative instruments including futures contracts and swap contracts. The Fund can use futures contracts, including interest rate futures, to reduce exposure to interest rate changes and to manage duration. The Fund can use swap contracts, including interest rate swaps, to hedge its exposure to interest rates. The Fund can borrow money for investment-related purposes including to purchase additional securities, which is another form of leverage. The Fund may also borrow to meet redemption obligations or for temporary and emergency purposes. Although the amount of borrowing will vary from time to time, the amount of leveraging from borrowings will not exceed one-third of the Funds total assets. The Adviser actively manages the Funds portfolio and adjusts the average maturity of portfolio investments based upon its expectations regarding the direction of interest rates and other economic factors. The Adviser seeks to identify those securities that it believes entail reasonable credit risk considered in relation to the Funds investment policies. In selecting securities for investment, the Adviser uses its extensive research capabilities to assess potential investments and considers a number of factors, including general market and economic conditions and interest rate, credit and prepayment risks. Each security considered for investment is subjected to an in-depth credit analysis to evaluate the level of risk it presents. The Fund can invest up to 25% of its total assets in tobacco settlement revenue bonds, which make payments only from a states interest in the Master Settlement Agreement (MSA), and up to 25% of its total assets in tobacco bonds subject to a states appropriation pledge, which make payments from both MSA revenue and a states appropriation pledge. The Fund will attempt to maintain a dollar-weighted average effective portfolio maturity of five years or less. However, it can buy securities with maturities of more than five years. Because of events affecting the bond markets and interest rate changes, the maturity of the portfolio might not meet the target at all times. Decisions to purchase or sell securities are determined by the relative value considerations of the portfolio managers that factor in economic and credit-related fundamentals, market supply and demand, market dislocations and situation-specific opportunities. The purchase or sale of securities may be related to a decision to alter the Funds macro risk exposure (such as duration, yield curve positioning and sector exposure), a need to limit or reduce the Funds exposure to a particular security or issuer, degradation of an issuers credit quality, or general liquidity needs of the Fund. The potential for realization of capital gains or losses resulting from possible changes in interest rates will not be a major consideration and frequency of portfolio turnover generally will not be a limiting factor if the Adviser considers it advantageous to purchase or sell securities. Show less