Top 5 Per Diem Mistakes Government Employees Make on TDY
Top 5 Per Diem Mistakes Government Employees Make on TDY
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Government per diem rules can be confusing, and even small mistakes may lead to lost money or delayed reimbursements. This guide breaks down the most common errors government employees make during Temporary Duty (TDY) travel—and shows you how to stay compliant while maximizing your allowance.
Mistake 1: Mixing up Lodging and M&IE rules
Lodging and Meals & Incidental Expenses (M&IE) are separate per diem categories, each with its own rules. Lodging typically requires itemized receipts and proof of payment showing the occupant’s name, dates of stay, nightly rates, and taxes. M&IE, on the other hand, is a fixed allowance for meals and minor expenses—it usually doesn’t require receipts, but the amount may be reduced on travel days or when meals are provided. Mixing up these rules can result in denied claims or delayed reimbursements, particularly if you’re miscalculating your per diem budget by incorrectly combining both categories.
How to fix it
- Keep lodging receipts itemized and readable with the correct address and dates.
- Track travel days and any provided meals to adjust M&IE correctly.
- Use one payment method for lodging to simplify proof of payment.
- Avoid the mistake of applying one type of per diem allotment to a separate category.
Mistake 2: Poor documentation and weak receipts
Common issues that lead to claim rejections include missing vendor details, blurry or illegible images, and combining personal and official charges. Screenshots that lack full billing information can cause delays, as can invoices that don’t match the travel itinerary or authorized duty location.
How to fix it
- Collect official invoices that show name, dates of service, taxes, daily rates, and a zero balance or payment confirmation.
- Separate personal purchases from official travel costs.
- Save PDFs rather than photos when possible and label files by date and category for quick review.
Mistake 3: Averaging per diem incorrectly
Many employees mistakenly average daily costs over the entire assignment instead of applying the correct per diem rate cap authorized for each day. This can lead to compliance issues, especially during longer stays or when monthly rates fluctuate according to the U.S. General Services Administration’s (GSA) published rates. It also creates problems when the duty location changes partway through the assignment.
How to fix it
- Apply the authorized daily rate for the official duty location for each calendar day.
- Recalculate properly if your location or status changes.
- Confirm agency specific rules for your TDY type before you submit.
- Find resources that give guidance, such as how to avoid this averaging pitfall.
Mistake 4: Ignoring the realities of longer TDYs
Longer assignments—typically 60 days or more—often offer better value with furnished housing instead of nightly hotel rates. Failing to plan accordingly can lead to higher costs, reduced comfort, and increased out-of-pocket risk, especially if essentials like utilities and internet are not included.
How to fix it
- Choose housing that fits your full TDY duration with predictable monthly costs.
- Confirm what is included such as utilities, internet, parking, and furniture.
- Align the lease dates with your official orders and save all addendums and delivery confirmations.
Mistake 5: Leaving value on the table
Many travelers stay within the per diem limits but miss opportunities to enhance their quality of life. With proper planning, it’s possible to choose compliant lodging and add essential furnishings using per diem—making a long assignment more comfortable and home-like without exceeding the allowance.
How to fix it
- Categorize needs up front such as fitness gear, pet items, or kitchen tools that improve daily life.
- Keep all confirmations for deliveries and pickups with dates and addresses.
- Work with a specialist that understands per diem rules and can structure invoices that voucher reviewers accept quickly.
Quick checklist for a clean voucher
- Correct daily rate not to exceed the authorized per diem rate, taxes, dates, and zero balance on every invoice.
- Itemized lodging receipts and clear proof of payment.
- No averaging per diem over the entire TDY duration.
- All documents saved as clear PDFs with consistent file names.
Why TDY Rentals helps
TDY Rentals specializes in compliant, long-term or short-term housing solutions across the United States. You select the lodging—we take care of the setup, utilities, and furnishings, and provide clear, agency-aligned documentation to keep your voucher process smooth. The result: greater comfort, fewer surprises, and full compliance.
