Who runs IFTA in Idaho, and where do you file the return?

The Idaho State Tax Commission, not the Idaho Transportation Department. The quarterly return is Form 3150, filed in the Tax Commission's Taxpayer Access Point (TAP). The handbook gives the current TAP address as idahotap.gentax.com and says TAP moves to tap.tax.idaho.gov beginning November 1, 2026. The Tax Commission does not mail paper returns. The IFTA line is (208) 334-7806, or (800) 972-7660 ext. 7806.

What does an Idaho IFTA license cost?

Idaho charges no separate license fee. The Tax Commission's IFTA Handbook says the cost of the license is $3.00 per decal set ordered, on the first application, at each renewal, and for extra decals during the year. A 30-day temporary decal costs $10 per unit, sold only at the Tax Commission offices in Boise.

When is the Idaho IFTA return due, and what does late cost?

April 30, July 31, October 31 and January 31, moving to the next business day on a weekend or state holiday. A return filed in TAP is on time until 11:59 p.m. Mountain Time on the due date. Late filing or payment costs 10 percent of the tax due or $50, whichever is greater, plus interest for each month late, with one day into a month counted as the whole month.

Can I amend an Idaho IFTA return in TAP?

No. The Tax Commission's reporting page says a Form 3150 cannot be amended in TAP. You download a copy of the original return from TAP, or get a paper copy from the IFTA Help Desk, check the Amended Return box and enter the corrected full figures. The handbook allows an amendment within three years of filing.

Idaho walkthrough

Idaho IFTA Filing Walkthrough (Quarterly)

Idaho IFTA runs through the State Tax Commission: apply in TAP or on Form IMC-2, $3 decal sets, and Form 3150 due by 11:59 p.m. MT.

By Evan Reid, Founder of Haul Handbook · Updated Sep 28, 2026 · 7 min read

Idaho puts IFTA with its tax agency. The Idaho State Tax Commission issues the license and decals, takes the quarterly Form 3150, and collects the tax. The Idaho Transportation Department handles your plates, so plan on two agencies and two logins. The Tax Commission publishes the whole program in one document, its IFTA Handbook (EPB00774, revised September 2026). The sourced fees, deadlines and penalty rules render on the Idaho IFTA page. This walkthrough puts them in the order you will meet them.

Step 1: confirm you need an Idaho license

You need one when you are an Idaho-based interstate carrier that runs IFTA qualified motor vehicles in Idaho and at least one other IFTA jurisdiction. The qualified vehicle test is the standard IFTA one: two axles with a gross or registered gross weight over 26,000 pounds, three or more axles at any weight, or a combination over 26,000 pounds. Recreational vehicles are excluded.

Idaho adds two branches worth sorting out first:

Trucks that rarely leave Idaho can register under Idaho's Full Fee (intrastate) registration instead of IRP. A Full Fee carrier that does cross into another IFTA jurisdiction can keep Full Fee, but then needs the Idaho IFTA license plus Full Fee registration or temporary registration permits in the other jurisdictions.
IRP-registered trucks must either hold the Idaho IFTA license or buy temporary fuels tax permits for travel in any IFTA jurisdiction, Idaho included. The Idaho permit side is laid out on the Idaho trip and fuel permits page.

Step 2: apply in TAP or on Form IMC-2

There are two ways in. Apply and pay online in TAP, the Tax Commission's Taxpayer Access Point, or mail Form IMC-2, Idaho Motor Carrier Application (IFTA only), with your payment. The Tax Commission mails the license and the decals once it processes the application.

Watch the TAP address this fall. The handbook gives the current address as idahotap.gentax.com/TAP/_/ and says that beginning November 1, 2026, TAP can be accessed at tap.tax.idaho.gov. A bookmark saved before November may point at the old address.

The fee is where Idaho reads differently from most states. There is no separate license fee. The handbook states that the cost of obtaining an IFTA license is $3.00 per decal set ordered, and the same $3.00 applies to extra decals during the year. A new licensee does not normally post a bond, though the Tax Commission can require one after late returns or late payments.

Step 3: file Form 3150 in TAP each quarter

The return is Form 3150, and TAP is the filing channel. The Tax Commission does not mail paper forms. Here is how a quarter goes, per the handbook's reporting section:

Log in to TAP and pick the period to file. TAP opens a virtual copy of Form 3150.
Enter fleet miles and gallons for each fuel type, so TAP can set your fleet miles per gallon. Count all miles and all gallons purchased.
Enter every jurisdiction you ran, with total miles, taxable miles and tax-paid gallons for each. TAP fills in the tax rates and totals.
If fleet fuel does not equal the tax-paid volume you reported, TAP shows an alert. It is a double-check and may flag nothing wrong; fuel bought tax-free at a tribal outlet is one case where the two differ.
Pay the balance in TAP, through the Tax Commission's E-Pay options, or in person at a Tax Commission office. Payments of $100,000 or more must go by ACH debit or ACH credit.

One Idaho rule changes the Idaho line itself: Idaho does not allow nontaxable miles on the Idaho line of the return. Idaho nontaxable miles go through the Tax Commission's separate fuels tax refund process for IFTA licensees.

The per-jurisdiction math is the same in every member state. Our how to file IFTA guide walks it, and the IFTA calculator runs your numbers against the current quarter's rates before you type them into TAP.

Step 4: hit the 11:59 p.m. cutoff

Returns are due on the standard IFTA clock: April 30 for January through March, July 31 for April through June, October 31 for July through September, and January 31 for October through December. A date on a weekend or state holiday moves to the next business day.

The Tax Commission's reporting page sets the time as well as the day: submit the return in TAP by 11:59 p.m. Mountain Time on the due date. You can file early and schedule the payment for the due date, which the handbook suggests as the way to avoid penalty and interest.

Two rules catch new filers:

File every quarter, even with no miles. A quarter with no travel or no taxable fuel still needs a return. Submit it in TAP with no numbers.
Know the late cost. Filing late, not filing, or not paying by the due date draws a penalty of 10 percent of the tax due or $50, whichever is greater, plus interest for each month late by postmark. One day into a month counts as the whole month. A partial payment goes to interest first, then tax, then penalty.

Step 5: fix a mistake on paper

This is where TAP stops. The reporting page says plainly that you can't use your TAP account to amend a Form 3150. The handbook gives the paper route and allows it within three years of filing the original:

Download a copy of the original Form 3150 from your TAP account, or ask the IFTA Help Desk for a paper copy.
Check the Amended Return box.
Enter the full correct figures, not the difference from what you first reported.
On Line 17, enter what you paid with the original return as a credit in brackets, and any refund you received as a positive number.

Step 6: renew by December 31 and keep records four years

The license and decals run January through December and expire December 31. Renew online in TAP and buy new decals every year. The Tax Commission will not renew a license until every IFTA return is filed and all tax, penalty and interest is paid, so a missed quarter blocks the renewal.

After renewal you have a two-month grace period to get the new license copies and decals onto the fleet, and you keep the old ones displayed until the new decals arrive. Each truck carries a copy of the license, paper or an accessible electronic copy, with one decal on the lower rear exterior of each side of the cab. A truck that needs to run before its decals arrive can use a 30-day temporary decal, $10 per unit, sold only at the Tax Commission offices in Boise, Monday to Friday, 8 a.m. to 4 p.m.

Keep fuel and mileage records, receipts included, for at least four years.

The Idaho shape, in short

Four things set Idaho apart. The program sits with the State Tax Commission, reachable for licenses, decals and returns at (208) 334-7806 or toll-free (800) 972-7660 ext. 7806, while plates stay with ITD. The only IFTA charge is $3.00 per decal set, with no separate license fee. Form 3150 files only in TAP, by 11:59 p.m. Mountain Time, and TAP moves to tap.tax.idaho.gov on November 1, 2026. And amendments leave TAP for paper. Current fuel tax rates by jurisdiction render on the IFTA rates by state table, and the plate side of the same fleet is on the Idaho IRP registration page.