Is Per Diem Taxable? When It Counts as Income

It's one of the first questions anyone asks the first time they see a per diem line on their pay slip: is this extra money, or is the taxman going to want a cut? The honest answer is "it depends," but the rules that decide it are narrower and more mechanical than most people expect.

The accountable plan is the whole ball game

Whether per diem is taxable comes down to a single IRS concept: the accountable plan. Under Internal Revenue Code Section 162 and the accompanying Treasury regulations, an employer's reimbursement arrangement qualifies as accountable — and therefore tax-free to the employee — only if it meets a three-part test. Fail the test and the arrangement becomes a "non-accountable plan," and every dollar paid is treated as ordinary taxable compensation, no different from salary.

Per diem is tax-free when…

• The payment does not exceed the federal per diem rate for that specific location and date — the GSA table for domestic CONUS travel, or the DoD/State Department tables for OCONUS and foreign travel.
• You (or your employer, on your behalf) file an expense report showing the time, place and business purpose of the trip within a reasonable period — the IRS treats 60 days as a safe-harbour window for substantiation.
• You return any amount paid in advance that exceeds your actual days of travel, typically within 120 days of when the excess was identified.

When per diem becomes taxable

If your employer pays more than the federal rate for your destination, the excess — not the whole payment, just the amount above the federal rate — is taxable and should be reported as wages. If you never file an expense report at all (a genuine "non-accountable plan"), the IRS treats the entire per diem as taxable, because there's no substantiation trail to prove it was a legitimate business expense rather than disguised pay. Flat travel stipends with no documentation requirement are the most common way per diem accidentally turns into taxable income — see our guide to travel stipends for how that differs from proper per diem.

The first-and-last-day catch

This is where a lot of well-intentioned DIY per diem calculations go quietly wrong. Because M&IE is only paid at 75% on your first and last travel day, paying a full day's M&IE on those two days technically overshoots the federal rate — even though it feels like a rounding error rather than a compliance issue. Our guide to the 75% first-and-last-day rule covers the mechanics in full; a compliant calculator applies the 75% rule automatically so the total stays inside the tax-free limit without anyone having to remember the exception by hand.

Provided meals reduce the tax-free amount too

If a conference or client provides a meal at no cost to you, the IRS expects that meal's value to be deducted from your M&IE claim for the day — claiming the full rate on top of a free meal pushes you over the accountable-plan ceiling for that day. See are provided meals deducted from per diem? for the specific dollar deductions by meal.

“An arrangement under which an employee is paid a mileage allowance or a per diem allowance... will be treated as satisfying the requirements... if the allowance is reasonably calculated not to exceed the amount of the expenses.”

— Internal Revenue Service, Revenue Procedure guidance on per diem substantiation, irs.gov

Self-employed workers: a different mechanism

The accountable-plan framework above applies to employees receiving reimbursement from an employer. Self-employed people don't receive a per diem payment from anyone; instead, they can deduct the federal M&IE rate (not lodging) for qualifying business travel directly on Schedule C, without needing to keep meal receipts, as long as they keep a log of dates, destinations and business purpose. See our guide to claiming mileage and travel deductions on your taxes for how that mechanism works alongside per diem.