Per diem is the single most misunderstood line on a set of TDY orders — and the one that decides whether a long course costs you nothing or quietly drains a few hundred dollars a month. Here is the whole system in plain English, written by people who file the same vouchers you do.
Per diem has two halves
Per diem includes a lodging allowance and M&IE (meals and incidental expenses). GSA sets CONUS rates; DoD sets non-foreign OCONUS rates, including Alaska and Hawaii; the State Department sets foreign rates. CONUS tables follow the fiscal year, while OCONUS rates can change during the year. Use your duty location and exact travel dates.
- Lodging is reimbursed at actual cost up to the cap. Spend less and you're reimbursed less; spend more and the difference is yours to eat. Receipts are required.
- M&IE is a separate daily allowance, generally without meal receipts. The first and last travel days ordinarily use 75% of the applicable M&IE rate. Government-provided meals and other circumstances can affect the allowance.
Pull the exact numbers for your duty location with the per diem calculator — it uses the same GSA feed DTS pulls for your authorization.
Why "at or below per diem" is the magic phrase
A military crashpad offers furnished lodging within your applicable allowance, with itemized receipts after payment. We review that allowance before making an offer. A published locality ceiling alone does not establish reimbursement eligibility; your orders, travel authorization and applicable lodging requirements still matter.
Hotels price at the cap too — and hand you 300 square feet, a mini-fridge, and a parking-lot breakfast. Same voucher, very different quality of life for three months.
The rules that bite people
Government lodging first
Government and preferred-lodging requirements depend on your destination, traveler category and authorization. Check with your travel office before choosing off-base housing and keep any required non-availability documentation. See Non-A lodging, start to finish and the on-base lodging calculator for planning support.
Long-term TDY and "flat rate" per diem
The former automatic 75% and 55% reductions based on TDY duration were repealed effective August 13, 2018. Staying beyond 30 days does not by itself trigger those reductions. Other properly authorized reduced rates and lodging restrictions can still apply. Check the current JTR and your authorization. The DoD repeal notice explains the change.
Receipts
Any lodging expense needs a receipt showing nightly rate, dates, taxes and fees, and a zero balance. A screenshot of a booking confirmation is not a receipt. Crashpads that live on TDY traffic hand you an itemized, DTS-ready statement at checkout as a matter of course.
Taxes and fees
Eligible CONUS lodging taxes are generally claimed separately from lodging; OCONUS treatment differs. Disclose cleaning, pet and other fees so the travel office can determine their treatment. Combining a fee with nightly rent does not make an otherwise ineligible expense reimbursable. Base Crashpads shows the agreed charges and taxes separately in its paperwork and receipts.
A worked example
Suppose an authorized lodging rate is $100 per night for 20 nights and $120 for the following 25 nights. The 45-night lodging estimate is $5,000 before eligible taxes. These are illustrative rates, not a quote for a specific base. Use the calculator for dated locality rates, then confirm the allowance for your orders. M&IE is calculated separately.
What we tell every guest
- Read your travel authorization for lodging, M&IE and any applicable restrictions.
- Check on-base availability and get the non-A number in writing if they're full.
- Book lodging at or below the rate, with itemized receipts guaranteed.
- Keep a running folder — orders, non-A, receipts — so the voucher takes ten minutes.
More detail lives in the per diem & reimbursement guide. When you're ready to price a stay, start with your base.