The Low Income Housing Tax Credit (LIHTC) program provides for the majority of new affordable housing units built in the U.S. and has resulted in the production of 1.5 million low income housing units since its inception in 1986. The LIHTC represents a radical departure from the structure of previous supply-side housing programs, which have generally relied on direct provision or subsidization of low-income housing. In addition to being a critical federal housing program, the LIHTC is of interest as an example of a novel type of tax expenditure program that is spreading to other policy domains. Under the LIHTC program, the government allocates tax credits to developers of low-income housing who then sell the credits, often via intermediaries, to investors in exchange for equity financing. Credits are subsequently claimed by investors on their tax returns. As a consequence, the tax beneficiary is an investor, rather than the provider or the targeted beneficiary of the subsidized service. We refer to this class of credits as “investable tax credits.”