The Hidden Risks of Averaging Per Diem Across Assignments

Averaging per diem across an entire assignment may sound like a simple way to track expenses, but it creates major compliance problems. Government employees and military members on Temporary Duty (TDY) must follow strict rules set by the General Services Administration (GSA) and their agency. These rules require per diem to be calculated daily, not averaged over time. Failing to follow this standard can result in lost reimbursement or even repayment demands.

What averaging per diem means

Averaging per diem happens when travelers take the total cost of lodging and meals for a trip and divide it across the number of days. While this can make personal budgeting easier, it does not match the rules for official reimbursement. Agencies and auditors expect per diem to be applied exactly as published for each calendar day of travel.

Why averaging per diem is a problem

• It can make a voucher appear inaccurate compared to official rates
• It hides overages on high-cost nights that exceed the per diem limit
• It may cause under-claiming, which leaves money on the table
• It creates confusion when orders are amended or extended

Examples of how averaging causes issues

• Hotel rate changes: If one night is above per diem and another is below, averaging hides the overage, but reimbursement may still be denied for the high night.
• Location changes: Different cities have different rates. Averaging across locations is never allowed.
• Travel days: M&IE rates are reduced on travel days, and averaging cancels this adjustment.

What the regulations require

The GSA per diem tables establish daily lodging and M&IE rates. Agencies require receipts and documentation that show compliance with those daily limits. Averaging is not supported under the Joint Travel Regulations (JTR) or the Federal Travel Regulation (FTR). Every day of travel must be claimed at its specific rate.

How to avoid averaging mistakes

• Check the official GSA per diem rates before booking lodging
• Keep receipts for each night with clear dates and rates
• Track meal adjustments separately for travel days
• Do not combine costs across locations or months

The bottom line

Averaging per diem may look like an easy shortcut, but it creates serious compliance risks. Each day of TDY must be documented and reimbursed according to the official rates. By avoiding this mistake, travelers protect their reimbursements and keep vouchers moving smoothly through the approval process.

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