IFTA Tax Rates in Idaho (2026)

Key numbers at a glance

Whether you base in Boise or just cross Idaho on I-84 and I-15 between Salt Lake City and the Pacific Northwest, the state's fuel tax follows every gallon you burn there. Under the International Fuel Tax Agreement you report those gallons on one quarterly return filed with your base state, and Idaho's 32-cent rate is what gets applied to your Idaho miles. The rate itself is almost boring — which is exactly what makes it useful for planning, because the number you budget in January is still the number you pay in December.

That stability is not true of the states around Idaho. Washington and Utah both index or adjust their rates and sit well above 32 cents, while Wyoming and Nevada land slightly below. For a truck running the I-84 corridor, the spread between those rates is real money — more on that in the fueling section below. Start with the full rate picture, then see the IFTA rates by state hub for the rest of the country.

IFTA tax rates in Idaho

Per the Idaho State Tax Commission, motor fuels tax rates are $0.32 per gallon across the board, effective July 1, 2015 and unchanged since. Rates as of Q4 2026 — confirm the current official IFTA matrix before filing.

Two footnotes matter. First, Idaho does not index its fuel tax to inflation, so — unlike Maryland or Illinois — there is no automatic July 1 bump to watch. The Tax Foundation's July 2026 table puts Idaho's combined gasoline tax burden near 33 cents once small fees are counted, but the IFTA-reportable rate is the statutory 32 cents. Second, Idaho's licensing and enforcement sit with the State Tax Commission, which also posts the IFTA rate matrix each quarter; IFTA, Inc. finalizes each quarterly matrix in early December for Q4.

Fueling strategy: Idaho versus its neighbors

Idaho borders six jurisdictions, and the diesel-rate spread is wide. The table below shows the rates on the current IFTA matrix (as of Q4 2026 — confirm the current official IFTA matrix; a dash means the jurisdiction does not list that fuel on the matrix).

The play: fuel in Idaho before a Washington leg, never the reverse. Washington's diesel rate is 27.5 cents a gallon higher than Idaho's. A truck burning 46 gallons crossing Washington at 6.5 MPG owes roughly $12.70 more in tax on those gallons than the same fuel bought in Idaho — and if you bought that fuel in Idaho, you prepay tax you were going to owe anyway. Westbound on I-84, Nevada (27.0 cents) and Wyoming (24.0 cents) edge out Idaho slightly, so top off there when it is convenient, but the differences are small enough that out-of-route miles — see our deadhead miles guide — usually cost more than they save. Run the exact numbers for your route with the IFTA calculator.

How Idaho IFTA affects your filings

The mechanics are the same everywhere; the rate is what changes. Taxable gallons equal Idaho miles divided by your truck's MPG, and tax owed equals those gallons times $0.32. Drive 500 Idaho miles at 6.5 MPG and you burn 76.9 gallons, which is $24.62 of Idaho fuel tax. Sum that across every jurisdiction on the trip, subtract the fuel tax embedded in your pump receipts, and the result is your net position — due or refund — on the quarterly return.

Deadlines do not move: Q1 closes April 30, Q2 July 31, Q3 October 31 and Q4 January 31, with late penalties typically running $50 to $100 plus interest per missed quarter. Two Idaho-specific habits keep filings clean. Match every receipt to a distance record, because mismatched paperwork is the number one audit trigger, and auditors usually ask for four consecutive quarters. And because Idaho's rate is flat, any divergence between your estimated and filed numbers points at MPG drift or missing receipts — not a rate change — so investigate early. Owner-operators budgeting the year ahead can treat Idaho fuel tax as a fixed 32 cents per gallon and focus attention on the indexing states around it.