Data Methodology & Sources
We publish open datasets on late-payment interest and tax rates. This page explains exactly how every figure is researched, cited, and verified — so you can trust it, and check it yourself against the original source.
(late-payment interest)
(VAT / GST rates)
statute or tax authority
The principle: every number is checkable
We do not ask you to take our word for it. Every rate in our datasets sits next to a link to its primary source — the controlling statute for US states, or the official government tax-authority page for VAT/GST. If a figure ever looks wrong, that citation is the fastest way to confirm or challenge it. Verifiability, not authority, is the point.
What we publish
Two reference datasets released as open data under CC BY 4.0, plus a smaller table of residential rent rules:
- US state late-payment interest — 51 jurisdictions (50 states + DC). The legal default rate that applies when a B2B contract is silent, the maximum rate a written B2B contract may charge, and the controlling statute for each. It also classifies every state into a three-bucket view of written-contract caps (26 no statutory cap, 12 conditional, 13 hard cap). → reference table · cap map · CSV · JSON
- VAT / GST standard rates — 42 countries & regions. The standard rate, a summary of common reduced rates, and the official tax-authority source for each. → VAT/GST guide · calculator · CSV · JSON
- Residential rent late-fee rules — 3 states. What each state's landlord–tenant statute allows a landlord to charge for late rent. Each row quotes the statute verbatim from the state's official code site and carries its own verification date. This table is not published as a download. → Massachusetts · Hawaii · New Mexico
Where the numbers come from
We cite the most authoritative source available, in this order:
- Primary law or official authority. The statute itself for US states
(e.g.
Cal. Civ. Code § 3289,Tex. Fin. Code § 302.002), or the government tax authority's own page for VAT/GST (e.g. HMRC, an EU member state's finance ministry, the ATO). - Official secondary — only when the primary page is unreachable. If a statute portal or authority page is down or blocks automated access, we fall back to another official government source that restates the same figure, and we record that in the entry's source note (for example, citing a national business portal when the tax authority's own page returns an error).
- Never an uncited aggregator. We do not copy numbers from other rate-listing sites. If we cannot trace a figure to an official source, it does not ship.
How we verify each entry
Two independent passes
Each of the 51 US jurisdictions and 42 VAT regions is first researched against its primary source, then independently re-checked against that same source. Where the two passes disagree, the entry is re-examined against the primary text and corrected before publication.
We cite, we don't paraphrase
The number on the page is the number in the cited source. Each entry also carries a short note recording any nuance a single figure can't capture — a dollar threshold, an exemption, an automatic trigger date, or which official portal we used when the primary page was unreachable.
Definitions, so the data is used correctly
- Legal (default) rate vs maximum written rate. For late payment these are two different numbers, and we publish both: the default is what state law supplies when the contract is silent; the max written is the ceiling, if any, two businesses may agree to in writing.
- The three B2B cap buckets. No statutory interest-rate ceiling on a written B2B rate (26 states — the rate ceiling only; other law, such as consumer-credit rules, can still apply), conditional (12 — a cap that applies depending on the amount, the debtor or how the rate was agreed), and hard cap (13 — a ceiling that reaches written B2B rates).
- Variable / formula-set entries (8 states). Some states set the default by a formula or a periodically-reset official rate. Those entries show the currently published figure with its effective period, and link the official page that resets it — check the link before relying on the printed figure.
- VAT standard vs reduced rates. We publish the standard rate; common reduced rates are summarized, but they vary by item — check the cited authority for specifics.
Updates & last verified
- US late-payment interest dataset — last full review August 19, 2026; 13 rows were re-checked after that and carry their own date (latest October 10, 2026). Every row shows its own verification date.
- VAT / GST dataset — last verified September 25, 2026.
- Residential rent late-fee rules — last verified September 25, 2026, with a date on each row.
Both datasets are regenerated from the verified source file at every site build, so the on-page tables, the downloadable CSV/JSON, and the citations never drift apart. When a figure changes at its source, we re-verify against the primary text and date the review.
Limitations — read before you rely on it
Not legal or tax advice. Our datasets are a general reference for business-to-business invoicing. Consumer credit and consumer tax rules are separate and stricter. Statutes and rates change, and courts apply them to specific facts. Always confirm against the linked official source — or a licensed professional in your jurisdiction — before charging, disputing, or filing.
License, citation & downloads
Both downloadable datasets are open data under CC BY 4.0 — free to use, share, and cite with attribution. Copy-ready citations sit beside each table, and the raw data is one click away:
Found an error?
We would rather be corrected than wrong. If a figure looks off, tell us with the entry and the official source — we re-check against the primary text and update with a dated note. That loop is exactly why every number ships with its citation.