1. What is per diem?

Per diem is a method of reimbursement for travel expenses that allows a set dollar amount per day -- no matter how much is actually spent. The rate is determined by the government and varies by city. See #3 below for links to per diem rate websites. 
Northwestern University has instituted the use of per diem for M & IE (Meals and Incidental Expenses) only.  

2. What expenses are included in the per diem M & IE rate?

When using per diem, there is no need to retain reciepts for:
  • Meals, 
  • snacks, 
  • buses, 
  • trains, 
  • tips and fees, 
  • bellhops, 
  • baggage carriers, 
  • hotel maids 
  • parking
  • most taxicab trips.  Not included: The cab rides between your home and the airport, and between airport and conference site -- four total -- save receipts for these, so you can claim these expenses in addition to per diem.  

3. When I use per diem, what costs must I keep track of for my Expense Report?  Which receipts are required?

Do retain receipts for the following: 

  • Conference registration fee,
  • airline ticket,
  • taxicabs between your home and the IL airport, and between the destination airport and conference/office site and back (four total),
  • hotel bill,
  • Internet bill,
  • parking fee if you parked your own car at the airport.

4. How do I know if I can use per diem?

For federally sponsored projects, verification must first be obtained that per diem is allowed on the grant.  The PI of the grant authorizes the use of per diem for his/her research group (students, visiting scholars, post docs, research professors, et al.) in advance of the trip.  

The use of per diem must be established before the trip commences. If you are traveling courtesy of the funding of your Advisor/PI, you must get her/his permission in advance in order to use per diem method.  

To use per diem, the trip duration must be more than 12 hours.

5. Where do I find the per diem rate for the city to which I’m traveling?


Note: The maximum allowed per diem for the first and last day of travel is 75% of the per diem rate. The city in which you have your first meal of the day is established as the per diem rate for that day. 

6. Can I request a lesser amount than the established government per diem rate?

Yes.  However, you must still provide the information from the government link indicating the M & IE per diem rate for the city and then note that you are opting for lesser amount, which might be more in line with your actual expenses.

7. Can I mix and match per diem and detailed receipt reimbursement for the same trip?

No.  Only one method of reimbursement can be used per trip, and the method you intend to use must be declared before the trip commences.  If you choose per diem, you may decide to opt for a lesser amount (see #5) after the trip. 

8. Is the cost of Internet included in per diem rate?

No.  If it’s itemized on your hotel bill, or billed separately, save the receipt: it will be reimbursed outside of the per diem rate. See #2 above for more expenses for which you do not need to retain receipts.

9. Can I get reimbursed for the cost of renting a car while I’m on travel and using the per diem method of reimbursement? (updated April 2012)

Probably not. If the traveler is using a rental car while on NU business travel, the entire cost of the rental car will most likely *not* be reimbursed if the traveler is asking for per diem.

Here's the exception: The rental car cost from the destination airport to the Conference Hotel/Agency Location/etc. can be reimbursed, and the return trip from to the Conference Hotel/Agency location/etc to the airport can be reimbursed.  These two costs are in place of taxi trips.  An Exception Form is required.

The cost of a rental car can be reimbursed completely if the traveler does *not* request per diem – but an Exception Form is required to explain why the rental car was deemed necessary. 

10. If I’m traveling overseas and have a long layover before continuing to my final destination, which city do I use for the first day’s per diem rate?

The general rule is to use the city in which you have your first meal.

The per diem rate for the first and last day of travel is 75%, regardless of the length of the trip.  This is consistent with the U.S. General Services Administration Federal Travel Regulations.

If you have further questions, please contact Carol Surma - phone: 847-461-3692, Office Tech L359, or talk to your division's Program Assistant.

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