NSPIRE Wire is independent and not affiliated with HUD.
Ask a housing developer what made their project possible and the answer is usually a percentage: 9 percent, or 4 percent. The two numbers refer to the twin streams of the Low-Income Housing Tax Credit, and the difference between them decides far more than arithmetic.
The Low-Income Housing Tax Credit finances nearly all new affordable rental housing in the United States, but the program is really two subsidies wearing one name. The 9 percent credit and the 4 percent credit follow different rules, flow through different channels, and support different deal structures. The distinction drives what gets built, where, and with what other financing attached. This explainer lays out the difference and why it matters for the policy fights now in front of Congress.
Both credits live in Section 42 of the Internal Revenue Code, enacted in 1986. Each lets investors claim a credit against federal taxes over a ten-year period for the cost of building or rehabilitating affordable rental housing. The percentages describe the approximate present value of the subsidy: the 9 percent credit is designed to deliver roughly 70 percent of a building's qualified basis, while the 4 percent credit delivers roughly 30 percent. In practice, the 9 percent credit goes to new construction and substantial rehabilitation, and the 4 percent credit goes to projects financed with tax-exempt bonds and to acquisition costs.
The split is not a policy preference layered on top of the statute. It is written into Section 42 itself, which defines the applicable percentage for each credit type and sets different allocation paths for each. The practical consequence: two projects with identical buildings and identical rents can be financed through entirely different channels, subject to entirely different scarcity, depending on which credit they claim.
Neither credit works as a direct government check. Developers sell the credits to investors, usually through syndicators that assemble national or regional funds, and the equity those investors pay becomes part of the project's financing stack. The deeper the credit percentage, the more equity a project raises per unit of eligible cost, which is why the 9 percent award can carry a modest project almost by itself while a 4 percent award covers only a slice. Everything else in the deal, the first mortgage, soft loans, deferred developer fees, rental assistance, exists to fill the gap the credit does not cover.
That structure explains the program's political durability as well as its constraints. LIHTC moves private capital into affordable housing rather than appropriating subsidy directly, but it also means the value of the credit rides on investor demand and tax appetite, which is why the rate floors mattered so much when floating percentages sagged.
The 9 percent credit is rationed. Each state receives an annual per-capita allocation authority, adjusted for inflation, and state housing finance agencies award it to developers through a competitive process governed by each state's Qualified Allocation Plan. Demand runs far ahead of supply: in most states, the credits available in a year cover only a fraction of the applications, so QAP priorities, such as location, affordability depth, and project readiness, effectively decide which affordable housing gets built.
The 9 percent credit's depth is its defining feature: at roughly 70 percent of qualified basis, it is the largest single equity source most affordable projects will ever see.
Because the 9 percent credit carries the deeper subsidy, it can make a deal work with little or no debt. That makes it the workhorse for new affordable construction, and it makes the annual allocation ceiling one of the most consequential numbers in housing policy. Congress raised the ceiling temporarily in 2018 and set a permanent floor under the 9 percent rate itself, which previously floated with federal interest rates.
For anyone trying to understand a specific project, the credit type is the first clue to its economics. A 9 percent award signals a competitive win under the state QAP and a financing stack that probably leans heavily on credit equity. A 4 percent award signals tax-exempt bonds in the stack, a larger mortgage, and usually additional public subsidy somewhere in the sources. Preservation deals, where an existing affordable property is acquired and rehabilitated, often combine an acquisition credit at the 4 percent rate with bond financing, which is why the 4 percent world dominates the preservation pipeline even though the 9 percent credit gets most of the attention.
The 4 percent credit works differently. It is not awarded from the competitive per-capita pool. Instead, it flows automatically with tax-exempt private activity bond financing: a project that finances at least 50 percent of its aggregate basis with qualifying bonds can claim 4 percent credits on the entire basis. Because the subsidy is shallower, 4 percent deals need more layers, typically larger first mortgages, soft debt from state or local sources, and often project-based rental assistance, to close their financing gaps.
Before 2021, the 4 percent rate floated monthly with federal borrowing costs, and in the low-rate years it sagged well below its nominal level, weakening bond-financed deals across the pipeline. Congress fixed a minimum 4 percent rate in the year-end 2020 legislation for qualifying bond-financed buildings, which is why the credit is now described simply as 4 percent rather than as a floating approximation.
The two credits interlock. Bond volume cap, the same limited pool of private activity bond authority that triggers 4 percent eligibility, is shared with mortgage revenue bonds and other uses, so states must choose how much housing gets through that channel. Pairing rules mean many large deals combine 4 percent credits with tax-exempt debt, while smaller or harder-to-finance projects chase the scarce 9 percent allocations. When Congress debates expanding the credit, the debate runs on both tracks at once: raising the 9 percent ceiling, and lowering the 50 percent bond financing test so more projects qualify for 4 percent credits.
That second track is what turned the 50 percent test into a live legislative issue. Lowering the threshold stretches bond cap further and lets more bond-financed projects claim credits, which is why it has appeared in every major affordable housing tax package in recent years.
Whichever credit a project claims, the trade is the same: tax benefits now in exchange for affordability restrictions that run for decades. Owners commit to income and rent limits for a 15-year initial compliance period, and in practice much longer, because extended use agreements typically keep restrictions in place for at least 30 years. State agencies monitor compliance and report violations to the IRS, and credit recapture is the enforcement hammer for deals that fall out of compliance during the first 15 years.
The applicable fraction is the mechanism that ties benefit to performance: only the share of a building that is actually rented to qualifying low-income households, measured by units or floor space, earns credits. A project that drifts below its committed fraction sees its credit stream shrink, which is why occupancy rules sit at the center of program integrity debates.
Both credit types sit inside the same compliance architecture: the applicable fraction that ties credits to low-income units, income and rent restrictions, and the long extended-use periods that keep properties affordable for decades. Neither credit type has ever carried the immigration-status screening that governs HUD's direct assistance programs, which is why proposals like the LIHTC Security Act, covered elsewhere in this publication, would cut across both the 9 percent and 4 percent worlds at once. A building's credit type tells you how it was financed; Section 42's occupancy and compliance rules, and any changes Congress makes to them, apply to the credit itself.
The credit's footprint is why these distinctions matter beyond development circles. LIHTC has financed the production or preservation of millions of affordable apartments since 1986, and it remains the primary federal engine for building new affordable rental housing. Policy changes that look technical, a floor under a floating rate, a percentage-point shift in a bond financing test, translate directly into how many units get financed in a given state in a given year. The Congressional Research Service's primers on the program, which track both the credit's mechanics and the live policy debates, are the reference point most housing policy coverage builds on.
The near-term legislative picture runs through the same tracks. Housing packages in recent Congresses have paired 9 percent ceiling increases with a lower bond financing test, and the credit's supporters treat both as the highest-yield production levers available without new appropriations. Whether either moves, and in what package, shapes the pipeline for years.
Watch the annual allocation notices for the per-capita ceiling, the continuing debate over the 50 percent bond test, and any tax legislation that moves LIHTC provisions. And watch how each state's Qualified Allocation Plan evolves, because the 9 percent competition is where policy preference becomes concrete: it decides which projects, serving which households, actually get built each year.
The Low-Income Housing Tax Credit is really two subsidies: the competitive 9 percent credit, worth roughly 70 percent of eligible costs, and the bond-linked 4 percent credit, worth roughly 30 percent. Both come from Section 42 of the tax code, but they flow through different channels and support different deal structures.
States award 9 percent credits from an annual per-capita ceiling through competitive rounds, and demand far exceeds supply. The 4 percent credit flows automatically with tax-exempt bond financing once a project meets the 50 percent bond financing test, so it depends on each state's bond volume cap rather than the credit ceiling.
Congress set permanent floors under both rates after years in which the floating percentages sagged below their nominal levels, most recently fixing the 4 percent minimum for qualifying bond-financed buildings in the 2020 year-end legislation.
The two credits interlock in practice: large deals pair 4 percent credits with tax-exempt debt and rental assistance, while the scarce 9 percent allocations go to projects that need deeper subsidy to pencil. Proposals to expand the program run on both tracks, raising the ceiling and lowering the bond test.
This explainer covers how each credit works, how the rules differ, and why the distinction shapes what affordable housing gets built.
Editorial Desk
The NSPIRE Wire Editorial Desk publishes source-verified reporting and analysis covering HUD policy, NSPIRE inspections, affordable housing finance, development, transactions, and the people shaping the industry.
Know something we should know? Have documents, corrections, or related developments on this topic? Send an editorial tip to our reporters.
