You can claim per diems for each night you spend in-country, and you'll be paid at the aid programme rate applicable at the beginning of your trip.
The per diem schedule is based on the United Nations Development Programme's Daily Subsistence Allowance which contains rates for the countries where most of the aid programme work occurs. These rates are reviewed and updated quarterly.
To get details for other countries’ per diems email PCD@mfat.govt.nz.
Where a married or de facto couple are working on an assignment together, the per diem rate is adjusted. Refer to your contract for more detail, or contact the MFAT officer responsible for managing the open tender.