Is GSA Per Diem Taxable? The Accountable Plan Test

Guides · Updated October 2026

Is GSA per diem taxable? Usually no. The IRS treats per diem paid at or below the federal rate as a reimbursement, not wages, so it stays off your W-2. But that tax-free status is conditional. It depends on three requirements the IRS calls the accountable plan, and when any one of them breaks, some or all of the per diem becomes taxable income.

Every January, a federal traveler somewhere opens their W-2 and does a double take. Thousands of dollars in per diem flowed through their travel card during the year, and Box 1 shows none of it. It looks like a mistake. It is not. Per diem paid under the rules is invisible to the tax return by design. The interesting question is what makes it visible.

Is GSA per diem taxable? The three-test answer

The IRS runs every travel reimbursement through the accountable plan test, from Publication 463. Three requirements, all of them, or the money is wages:

Business connection. The travel has to be for work. Personal days tacked onto a trip do not count, and commuting never counts.
Substantiation. You file an expense report showing the dates, the destination, and the business purpose, within a reasonable time. Sixty days is the safe harbor.
Return of excess. If you received more than the substantiated amount, the difference goes back to the employer within a reasonable period. One hundred twenty days is the safe harbor.

When all three hold and the per diem stays at or below the GSA rate for the location, the payment is not taxable income. No income tax, no Social Security tax, no Medicare tax, for you or the employer. It does not appear in Box 1 of your W-2.

The three ways it becomes taxable

First, and most common: the per diem exceeds the federal rate. Only the excess becomes taxable, but it becomes fully taxable as wages, subject to income tax withholding and FICA, and the employer reports it in Box 1. This is where the first-and-last-day rule quietly bites federal travelers. GSA cuts the meals and incidental expenses rate to 75 percent on travel days. If a voucher pays the full M&IE rate on a departure day, the 25 percent difference is an overpayment, and overpayments are taxable.

Second: no paperwork. If the traveler never files the expense report, the arrangement fails the substantiation test, and the entire per diem becomes taxable, not just the excess. A flat travel stipend with no voucher behind it gets reclassified as wages dollar for dollar. This is where most compliance failures start: the money was legitimate travel money, but nobody documented it, so the IRS treats it as pay.

Third: the assignment stops being travel. Per diem covers temporary travel, which the IRS defines as expected to last, and actually lasting, one year or less. If an assignment is extended past the one-year mark, it is no longer travel, and the per diem becomes taxable income from the day the extension is known. Long-term federal details are the classic case. A traveler on month eleven of a twelve-month assignment is fine. The day the assignment extends to month fourteen, the tax treatment flips.

What this means on your return

For the typical federal traveler filing proper vouchers at GSA rates, the answer is simple: nothing to report. The per diem is not income, not a deduction, not a line on the return. It exists only in the travel system.

The action items are equally simple and almost nobody does all three: file the voucher within 60 days, return any excess within 120 days, and watch the calendar on long-term assignments. The tax-free status of per diem is not a property of the money. It is a property of the paperwork around the money. Keep the paperwork clean and the W-2 stays clean with it.

Use our GSA per diem calculator to check the current rate for your destination before you travel, so the voucher matches the table and there is no excess to argue about later.

Traveling on orders?

Look up the current GSA lodging and M&IE rates for your destination before you file the voucher.

Look Up Per Diem Rates

Frequently asked questions

Is GSA per diem taxable income?

Generally no, when it is at or below the federal rate and paid under an accountable plan. It does not appear in Box 1 of your W-2.

What is the IRS accountable plan?

Three requirements from IRS Publication 463: the travel must be for business, you must substantiate dates, destination, and business purpose (60-day safe harbor), and you must return any excess over substantiated expenses (120-day safe harbor).

What happens if per diem exceeds the GSA rate?

The excess becomes taxable wages, subject to income tax withholding and FICA, and the employer reports it in Box 1 of the W-2.

Is per diem taxable if I never file an expense report?

Yes. Without substantiation the arrangement fails the accountable plan test and the entire per diem is reclassified as taxable wages, not just the excess.

Does the 75 percent first-and-last-day rule affect taxes?

It can. GSA pays 75 percent of the M&IE rate on travel days; a voucher that pays the full rate creates an overpayment, and the excess is taxable wages.

Is per diem taxable on assignments longer than a year?

Yes. Travel expected to last more than one year is not temporary travel under IRS rules, so per diem becomes taxable income from the day the extension is known.