How this stays accurate.

Where every check comes from

Every rule in the scanner names its primary source: the FAR or DFARS clause, the 5 CFR 1315 section, the PIEE/WAWF official guide, or the DFAS/DCAA published document it implements. The complete library is public at the rules index, including rules built on documented practice rather than regulation, which say so plainly and only ever render as advisories. The rule count shown on the site () is the live count of the shipped library. We never quote a bigger number than the index shows.

How the interest math is computed and tested

The calculator implements the Prompt Payment computation as 5 CFR 1315.10 specifies it: interest accrues daily on a 360-day year basis; unpaid interest compounds into principal every 30 days; accrual is capped one year after the due date; amounts under $1 need not be paid. The due date is the later of receipt-plus-30 or acceptance-plus-30 for standard invoices (FAR 32.904(b)(1)), with constructive acceptance on the 7th day after delivery when acceptance isn't recorded, or is recorded later than that (FAR 52.232-25(a)(5)(i)). A due date that falls on a weekend or federal holiday is met by payment on the next business day (5 CFR 1315.4(h)); when payment is late anyway, interest still runs from the day after the original due date.

The rate. We apply the Treasury Prompt Payment rate in effect on the day after your due date, held for the whole delinquency (31 U.S.C. 3902(a); FAR 32.907), from the published table at fiscal.treasury.gov. It is currently for . When your due date falls in a period whose rate Treasury hasn't published yet, the calculator says ESTIMATE on its output instead of pretending.

The FAR Overhaul. DoD class deviation 2026-O0022 (effective Feb 1, 2026) applies the Revolutionary FAR Overhaul text of Part 32 to DoD awards. We diffed it against the legacy text: FAR 32.904, 32.905(b), 32.906, 32.907 and clause 52.232-25 (with Alternate I) are word-for-word unchanged, so every Prompt Payment citation on this site resolves under either version.

Testing. The engine's outputs are verified against independent hand computation to the cent, including cases whose accrual spans a Jan 1 / Jul 1 rate reset, a due date on a weekend, and an acceptance recorded late. The golden cases ship with the code (tests/golden_interest.json) and are re-run on every change. The rate table is refreshed every January and July when Treasury publishes.

The golden cases run on every change to the engine or the library. Library verified . Corpus re-verification runs quarterly.

What Debenda will never tell you

• We never say “approved for payment.” Only the government approves payment.
• We never guarantee an outcome. We tell you what the rules say and what historically gets bounced, with the citation attached.
• Estimates with no published statistic behind them are marked ESTIMATE and rendered as advisory only.

Corrections

The public corrections log is empty so far. If you find an error in any rule, citation, or computation, email nadav@debenda.com. Confirmed errors get fixed, dated, and listed here permanently. We'd rather fix a rule than defend one.