Interactive feasibility tool · Post-OBBBA defaults

Capital Stack Builder.

A real sources & uses model. Size LIHTC equity from eligible basis and permanent debt from a transparent NOI → DSCR → mortgage-constant build-up — then see the funding gap. Every assumption (pricing, opex, vacancy, DSCR, rate, MIP, amortization) is an editable input, not a hidden constant.

NOI÷DSCR
supportable-debt sizing
Editable
every assumption visible
9% / 4%
LIHTC + bond deals
Sources=Uses
live gap / surplus check
Updated May 11, 2026 · Post-OBBBA landscape

How the builder works

This is a working sources & uses model. Uses is your total development cost. Sources are computed from inputs you control: LIHTC equity = eligible basis × boost × applicable fraction × rate × 10 × credit price; permanent debt = stabilized NOI ÷ DSCR ÷ the annual mortgage constant (including MIP). Soft debt and deferred developer fee are sources you enter; the leftover is the funding gap (or surplus). Nothing is hardcoded — change any assumption and the stack responds. It loads pre-filled with HUD's worked example so you can see a real deal immediately. It is still a feasibility screen, not a substitute for your syndicator's underwriting.

Interactive tool

Capital Stack Builder.

Deal & uses total development cost = total uses
LIHTC equity basis × boost × fraction × rate × 10 × price
Line-item build-up: Eligible Basis Calc →
Permanent debt NOI ÷ DSCR ÷ mortgage constant (incl. MIP)
FHA only; 0 for conventional
Other sources you provide these; the rest is the gap
HOME, HTF, state, AHP

What you control

Nothing material is hardcoded. Every driver below is an input you set, and the stack recomputes live:

  • LIHTC equity. Eligible basis (enter it as a % of TDC or override with a dollar figure — or build it line-by-line in the Eligible Basis Calculator and hand it over), the 130% boost, applicable fraction, credit rate, and credit price are all editable. Equity = eligible basis × boost × fraction × rate × 10 × price.
  • Permanent debt. Built from a transparent NOI: gross potential rent − vacancy + other income − operating expenses − replacement reserves. Debt = NOI ÷ your DSCR ÷ the annual mortgage constant, where the constant is computed from your interest rate and amortization with MIP added on (the FHA method). Set MIP to 0 for conventional/GSE debt.
  • Other sources. Soft debt (HOME, HTF, state, AHP) and deferred developer fee are sources you enter. The residual is the funding gap (or surplus).
  • 4% + bond deals. Switching to 4% sets the credit rate to the 4% floor and shows the tax-exempt bond as a memo only — bonds finance construction and are taken out by the permanent loan at conversion, so they are not double-counted as a permanent source.
  • Loads with HUD's worked example (100 units, $125k/unit TDC, 75% basis, $0.90 price; $700 rent, 7% vacancy, $4,500 opex, $500 reserves, 1.2× DSCR, 4.5% / 30-yr, 0.45% MIP) so you start from a real, checkable deal.

What this builder doesn't do

  • It doesn't build your uses. Total development cost is a single input. For the cost-side build-up (hard cost, contingency, GC, soft costs, developer fee) use your development budget; for the eligible-basis portion use the Eligible Basis Calculator.
  • No state HFA specifics. Bond-cap rules, gap-subsidy programs, and QAP sizing constraints vary by state and are not modeled. See the relevant state HFA page.
  • It doesn't quote rates or pricing. Interest rate, MIP, DSCR, and credit price are your inputs — the defaults are illustrative, not quotes. Confirm execution (FHA 221(d)(4)/223(f) vs GSE) with your lender and pricing with your syndicator.
  • No income-averaging or unit-mix detail. The applicable fraction is a single input; an income-averaged project has a unit-by-unit designation that affects basis and rents.
  • Not an underwriting model. It is a feasibility screen — a full pro forma with a 15-year cash flow, lease-up, and exit comes from your syndicator.

What to do with the output

Read the gap. A small gap (<10% of TDC) is usually closable with normal state/local soft money and deferred fee. A large gap (>25%) means the deal needs deeper subsidy, lower cost, or higher NOI — tune the inputs to see what closes it. A surplus means you can reduce hard debt (improving coverage) or equity. For deals that pencil, the next step is your syndicator's full underwriting — not this tool.

Sources

  • IRC § 42 (LIHTC) — applicable percentages, eligible basis, qualified basis, basis boost
  • IRC § 42(h)(4)(B) — bond financed-by test (25% threshold for buildings placed in service in taxable years beginning after Dec 31, 2025; ≥5% of aggregate basis must be financed by bonds with an issue date after Dec 31, 2025)
  • IRC § 42(d)(5)(A) — federal grants excluded from eligible basis (grant-financed costs are not counted)
  • P.L. 119-21, One Big Beautiful Bill Act, enacted July 4, 2025

Disclaimer

The Capital Stack Builder is a feasibility-stage screening tool with simplified inputs and assumptions. It is not an underwriting model and does not substitute for a full pro-forma from your accountant or syndicator. Equity pricing, debt rates, opex ratios, and many other inputs vary widely by market and deal. Always confirm modeled numbers with a qualified professional before relying on them for a transaction. This is educational content and is not legal, tax, or financial advice.