The details you'll need about reimbursing foreign per diem allowances are given in the Expenses Guidance and Procedures document, section 16.4.1. HMRC has issued detailed guidance regarding the use of per diems including the following:

“rates are intended to represent... expenses that employees incur during a period spent in a foreign country. Rates include:

• A 24 hour rate. This is intended to cover the total cost of meals in a period of 24 hours plus the cost of daily travel
• A 10-24 hour rate, which is intended to cover subsistence expenses for any period of more than 10 but less than 24 hours
• An over 5 hour rate which is intended to cover subsistence expenses for any period of more than 5 but less than 10 hours”

The hourly rates have to be measured by reference to the times of arrival in and departure from the foreign country.

Example
You arrive in Buenos Aires at 3pm on Monday and stay in a hotel in the city. You leave on the 9am flight on Thursday.
The maximum that can be claimed is:

Rate	No. days/nights	ARS (Argentine Peso)	Total ARS
Hotel accommodation	3		Receipts
24 hour subsistence rate	2	391	782
10 hour subsistence rate	1	346	346
Total			1,128 plus hotel receipts

Please note that the type of per diem you can claim depends upon the type of accommodation you stayed in. If you stay as a guest of a private individual or a company, a maximum of 10% of the subsistence rate may be claimed. If you stay in a flat with laundry and or cooking facilities a maximum of 80% of the subsistence rate may be claimed for the first seven days of your visit, followed by a maximum of 50% for subsequent days.

Please note that per diems are not available for all countries/cities, so the accompanying tables should be checked for availability before claiming a per diem. The rates shown are the maximum permitted - departments are free to set their own rates below these maxima if the relevant budgets cannot meet the full allowance.

If you intend to hire a car you are advised to claim for your trip on the basis of receipts and not claim a per diem as well. This is because the per diem rate includes travel and you cannot, therefore, claim for both car hire and a per diem.

Expenditure in locations where there is not a per diem, and foreign visits which have genuinely higher costs than those allowed for in the per diem rates will be reimbursed on a receipts basis. Members of staff are expected to exercise reasonable restraint when incurring expenses on overseas business on behalf of the University. When claiming on a receipts basis, full documentary evidence of the expenditure must be supplied. Provided these expectations are met, full reimbursement of expenditure necessarily incurred on the University's behalf will usually be made.