The daily allowance, also called “per diem,” is a fixed reimbursement of additional expenses for meals (food and drink) incurred on business trips within Germany. The amount of the daily allowance – also called daily rate – is based on the German Income Tax Act (§ 4 (5) Sentence 1 Point 5 Sentence 2 EStG) and depends on the duration of the trip (days and hours). Different amounts apply for trips to other countries (see International daily allowance).
The daily allowance is part of the travel expense allowance under the German Federal Travel Expenses Act (BRKG) and may thus be billed as travel expenses in the respective amount by publicly funded artists.
Self-employed artists may deduct per diems and other travel expenses from their taxes as business expenses.

Quelle: Andreas Reich (2012): BRKG (only available in German)