Tax-backed       debt obligations are the debt instruments issued by counties, states,       cities, towns, special districts and school districts. These are secured       by some form of tax revenue and are classified into three types. They are       as follows:
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General           Obligation Debt: General Obligation Debt is a municipal security           secured by the taxing and borrowing power of the municipality issuing           it. In fact, they are backed by the credit and taxing power of the           issuing jurisdiction rather than the revenue it receives from a given           project in hand. This is the feature, which influences the investor to           invest in these securities. 
In       addition to above back up, certain identified fees, grants and special       charges also secure some of the general obligation securities. These are       the amounts, which provide additional revenue to the State outside the       purview of the general fund. Due to this dual nature of the revenue       sources, these securities are also known as double-barreled in security.
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Appropriation-Backed           Obligations: Appropriation-Backed Obligations are securities           issued by agencies or authorities of several States to meet their           entity obligations. These securities are backed up with the           appropriation of funds from the State general tax revenue. The state           legislature should approve this appropriation of funds from the           state's general tax revenue. However, the state's obligation is           not binding. When a debt obligation is backed by such non-binding           pledge of tax revenue, it is known as moral obligation bonds. The           moral obligation pledge helps in enhancing the creditworthiness of the           issuer. Lease-backed debt is another type of appropriation-backed           obligation. 
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 Debt           Obligations Supported by Public Credit Enhancement Programs: A           moral obligation is a form of credit enhancement provided by the           state. This obligation of the state is neither legally enforceable nor           legally binding. However, the public credit enhancements can be made           legally enforceable if the state or a federal agency guarantees the           issue or when there is an obligation to automatically withhold and           deploy state aid to pay any defaulted debt service by the issuing           entity.