An owner-operator's quarter is a pile of trips and fuel receipts; the return is per-jurisdiction columns on Form IFTA-101. Between the two sit three rules that free templates and hand math reliably get wrong. One: the Kentucky and Virginia surcharge is owed on FULL taxable gallons even when the state's fuel line is a credit, because a surcharge cannot be prepaid at the pump — on the worked example shipped in the file, Kentucky's fuel line is a $12.32 credit and its surcharge line still owes $9.87. Two: a credit in one jurisdiction offsets tax due in another on the same return, at that jurisdiction's own rate — the example's $39.20 Texas credit pays down the Ohio balance without a cheque changing hands. Three: the rounding is specified, not stylistic — miles and gallons to whole numbers half-up, fleet MPG to two decimals, one fleet MPG for every jurisdiction. This workbook carries all three, and its Sources sheet cites the instruction line each one comes from.

You type where you already live: date, truck, jurisdiction, miles, gallons — one log row per trip or per fuel stop, 420 rows deep. The Quarter Summary sheet computes fleet MPG the specified way and rolls every row up by jurisdiction; the IFTA-101 Worksheet turns the rollup into the return's columns — taxable gallons, tax-paid gallons, net gallons, tax or (credit) per jurisdiction, surcharge lines inserted for Kentucky and Virginia, and a grand total that nets credits against debits. On the shipped example — three states, 6.35 fleet MPG — the quarter closes at $61.75 due, and you can trace every cent of it from the log rows to the total.

Rates are the reason spreadsheet templates in this niche die: they change every quarter. Our answer is structural, not a promise. The Rates sheet is generated from a rate matrix captured from TWO independent publications with a name-by-name cross-check — 57 diesel jurisdictions for Q2 2026, captured 2026-09-02, status and both sources printed on the sheet. A rate the sources do not publish stays an empty cell with a note saying why — Oregon has no IFTA fuel tax on diesel, and Indiana publishes no diesel surcharge for 2026 — never a guessed zero. When the next quarter's matrix is captured and cross-checked, the workbook is rebuilt from it; your order page always serves the current build, and re-downloading is free, as it is for everything we sell.

The whole book was verified against an independent Python model of the IFTA-101-I rules before it was allowed to ship: 22 scenarios — every model fixture plus multi-truck logs, an all-credit quarter, Oregon-only miles, taxable-mile splits — each written through the same yellow cells you will type into, recalculated by LibreOffice, and compared cell by cell: 976 assertions, zero mismatches. A mutation self-test proves the harness would actually catch a broken formula. The Checks sheet then keeps 12 live self-checks running on YOUR numbers — fleet MPG recomputed two ways, surcharge gallons equal to fuel-line gallons, credits carrying real rates, log codes that are real jurisdictions — so a typo shows up before the return does.

Honest limits, printed inside the file and repeated here: diesel only (other fuel types have their own rate tables and exemptions); KYU, New Mexico, New York HUT and Oregon weight-distance taxes are separate programs this workbook does not file; late-return interest is not computed; filing due dates are not printed anywhere in the book, because we have not yet captured them from an official source and we do not print unverified constants. The files are in English; totals are in US dollars.