A municipal bond that is backed by the pledge of the issuer (generally a city or municipality) to raise taxes, without limit, to service the debt until it is repaid. Because of this feature, unlimited tax bonds may have higher credit ratings and offer lower yields than other comparable municipal bonds of the same maturity. 

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While the issuer of unlimited tax bonds in theory can raise taxes at an unlimited rate, in practice it may be difficult to raise taxes beyond a certain point. One of the factors that credit analysts use to rate such bonds is the ability of the issuer to enforce penalties against and recover taxes from delinquent taxpayers.