Methodology
Data Sourced from Official State Tax Authorities
Calculation logic — the exemptions, brackets, and rates each calculator applies — is checked against state Department of Revenue guidance and, where relevant, primary legislative records (bill text, signed-law status) before publishing. This is not the same as a CPA review: no CPA has reviewed this app's calculation logic. Each state's data file documents exactly what was checked and what remains unverified — see `data/inheritance-tax-data.ts` in the source for the specifics.
Federal data sourcing
Federal figures referenced anywhere on DueMATH (such as the federal estate tax exemption) are sourced from current IRS revenue procedures and rate schedules. This means the numbers are sourced from the IRS — it does not mean the IRS has reviewed, endorsed, or certified this calculator. We deliberately don't use the term “IRS-Compliant” anywhere on this site, because no such formal review has happened and that label would imply one had.
Reviewed August 2026
This date is the most recent “last verified” date across every calculator's source data, computed from the data files themselves rather than typed in by hand, so it can't silently drift out of sync. It's a ceiling, not a floor — some calculators were verified more recently than others. Each calculator page shows its own specific last-verified date and source note near the top, so you can see exactly how current the figures you're using actually are, rather than assuming every calculator is equally fresh.
Confidence levels
Not every figure was verified the same way. Where a calculator says verified against primary source, that number was checked directly against a state Department of Revenue page, a signed bill, or an IRS revenue procedure. Where it says approximation or shows an “Estimated” badge, the underlying figure came from a secondary summary (e.g. Tax Foundation) or uses a simplified calculation (like a flat top rate instead of a full bracket table) — treat those numbers as a starting point, not a filing number.
Educational intent and non-endorsement
DueMATH is designed to help minimize interest by making total lifetime cost visible, not just the monthly payment — informed by anti-usury principles as a product-design philosophy, not a religious or legal certification. DueMATH never claims a product, offer, or calculator result is “Sharia-certified,” “halal,” or “haram,” and displaying or comparing a financial product never constitutes an endorsement of it. See the full Educational Intent, Anti-Usury principles, and Non-Endorsement of Interest-Based Products section on the Terms of Use page.
What happens to your data
Short version: calculations run in your browser and nothing you type is sent to us, except if you use the optional AI explanation feature. Full details on the Privacy Policy page.