Accountable Reimbursement Plans
The Contractor's Guide to Paying Yourself (and Your Crew) Back Tax-Free
If you run a contracting business and you're reimbursing yourself or your crew for mileage, per-diem, or job-related expenses, there's a good chance you're either overpaying in taxes or setting yourself up for an IRS headache. The fix is a formal accountable plan. Most contractors have never heard the term, let alone put one in writing.
Here's what it is, how to use it for per-diem and vehicle costs, and the exact steps to get one in place.
What an Accountable Plan Is (Plain English)
An accountable plan is simply a reimbursement arrangement that meets IRS rules so that money you pay out for business expenses (mileage, meals on the road, tools, per-diem) isn't treated as taxable wages.
Without one, any reimbursement you hand out (to yourself as an S-corp owner, or to W-2 employees) legally has to run through payroll as extra compensation. That means it's subject to income tax withholding and payroll taxes, on both sides. With an accountable plan, that same reimbursement passes through tax-free, as long as three conditions are met:
Business connection — the expense has to be for a legitimate business purpose (driving to a jobsite, lodging while traveling for a project, etc.).
Substantiation — the person being reimbursed has to show what was spent, when, and why, within a reasonable time.
Return of excess — any amount advanced that exceeds actual substantiated expense has to be returned within a reasonable time, not just kept.
For a contracting business with crews driving between job sites, staying overnight on out-of-town jobs, or fronting their own fuel and tools, this isn't a nice-to-have. It's often the difference between reimbursements that quietly inflate your payroll tax bill every year and reimbursements that don't cost you or your crew a dime in extra tax.
If you want the full guide, check out my Contractor Tax Playbook.
Per Diem Basics for Crews on the Road
Per-diem (read: a flat daily rate for meals and incidental expenses, sometimes lodging too) is one of the most useful and misused tools available to contractors with traveling crews.
How it works: instead of collecting receipts for every meal, you pay a set daily rate tied to the location the crew is working. The IRS publishes standard rates through the General Services Administration (GSA) for lodging and meals & incidentals (M&IE) by city and county, with a "high-low" simplified method available for businesses that don't want to track rates city by city.
What still has to happen, even with a flat rate:
You need a written per diem policy that specifies the rate and how it's applied.
The crew member still has to substantiate the time, place, and business purpose of the travel…just not the exact dollar amount of each meal.
Per diem paid above the federal rate is taxable on the excess. Paid below the federal rate is fine, you just can't deduct more than what was actually paid.
Common pitfalls:
Paying per-diem for local, non-overnight travel generally doesn't qualify and becomes taxable wages.
Rounding or flat-rating without documenting the trip dates and locations that justify the amount.
Mixing per-diem with reimbursed actual lodging costs without separating the two in your records.
Forgetting that per-diem rates differ by locality. A flat company-wide number that ignores where the GSA rate is actually higher or lower creates both under- and over-payment risk.
Vehicle Policy: Business vs. Personal, Mileage vs. Actual
Vehicle costs are the other big one for contractors, and there are two separate decisions to make.
Business use vs. personal use. Only the business-use portion of a vehicle's cost is reimbursable or deductible. Commuting from home to a regular job site is generally treated as personal, not business, mileage. Driving between job sites during the day, or to a supplier, generally is business mileage. Crews using company trucks for personal errands need that use logged and, in some cases, treated as a taxable fringe benefit.
Mileage rate vs. actual expense method. There are two ways to reimburse vehicle costs:
Standard mileage rate — a flat per-mile rate set annually by the IRS, meant to cover gas, maintenance, depreciation, and insurance combined. Note that the IRS made a mid-year adjustment in 2026: the rate was 72.5 cents per mile for miles driven January 1–June 30, 2026, and rose to 76 cents per mile for miles driven July 1–December 31, 2026, reflecting a jump in fuel prices. If you're reimbursing crew mileage this year, make sure you're applying the right rate to the right half of the year.
Actual expense method — reimbursing (or deducting) the real cost of fuel, repairs, insurance, and depreciation for the business-use percentage of the vehicle. This requires more record-keeping but can be worth more for vehicles with high actual operating costs, like heavy trucks.
Who qualifies: this applies to owners driving their own vehicle for business, W-2 employees using personal vehicles for work, and company-owned vehicles used partly for personal purposes. The reimbursement method has to be applied consistently and documented — you can't switch methods mid-year for the same vehicle without consequences.
3-Step Setup Checklist
Getting an accountable plan in place is more paperwork than complexity. Here's the order to do it in.
1. Put the policy in writing. A short document that states: what counts as a reimbursable expense (mileage, per-diem, tools, lodging), the rates used, the deadline for submitting expenses (commonly 60 days), and the deadline for returning any excess advance (commonly 120 days). This doesn't need to be long, but it needs to exist and be adopted. This could be board minutes or an owner resolution for an S-corp, or a signed policy for a partnership or sole prop with employees.
2. Build the substantiation process. Decide how mileage logs, per-diem trip records, and receipts get submitted. A simple spreadsheet, an app, or a standard expense form works. The substantiation has to show the amount, date, place, and business purpose for each expense. This is the piece most contractors skip, and it's the piece the IRS actually checks if a reimbursement is ever questioned.
3. Route it correctly through payroll and books. Reimbursements under an accountable plan should not appear on a W-2 as wages and should not have payroll tax withheld. They get coded as a reimbursement/expense in your bookkeeping, paid separately from payroll (or as a clearly separated line item), and tracked against the substantiation records from step 2. If your payroll provider or bookkeeper doesn't already separate this out, that's a conversation to have this week.
Common Mistakes
Treating reimbursements as extra wages by default. This is the single most expensive mistake. It means you and your crew are paying payroll tax and income tax withholding on money that could have been tax-free.
Sloppy or after-the-fact mileage logs. A log built weeks later from memory doesn't hold up. Contemporaneous logs — even a simple daily note of miles and destination — are what substantiation actually requires.
No written policy at all. Verbally agreeing to "just pay for gas" doesn't meet the business-connection or substantiation requirements on its own.
Not returning excess advances. If you advance per-diem or mileage money and the actual expense comes in lower, that difference has to be returned within a reasonable time or the entire advance can be reclassified as taxable.
Applying the wrong mileage rate for the period. With the mid-year 2026 rate change, this is an easy one to get wrong right now.
Get This Set Up Correctly
An accountable plan is one of the more overlooked pieces of a contractor's tax setup, and it's also one of the easier ones to fix once you know it's missing. If you want a second set of eyes on your reimbursement policy, per diem rates, or vehicle mileage setup, or you're not sure whether your current approach would hold up, book a 30-minute Contractor Tax & Retirement Checkup and we'll walk through it together.
This post is for general informational purposes and isn't tax or legal advice for your specific situation. Rates and rules referenced here reflect 2026 IRS guidance and may change.