Flat-rate daily allowance for foreign business trips

We have answered your question in a video: https://vimeo.com/1071774265?share=copy

Thank you for the clear explanation! It's a shame that this is not allowed. Can I add proof of payment from the lessons I have taken and experiences I have booked as training to my accounts? Are there any other costs that I can claim in this context (accommodation, transport, etc.)? What requirements must these proofs of payment meet?

Actual costs, based on invoices, proof of payment, etc., can of course always be claimed if they are work-related. Domestic or foreign, that doesn't matter in principle. As long as you:

• Have proof (it doesn't have to be an invoice, it can also be a payment overview, receipt, etc.)</

  Can prove the payment (there is a tolerance for cash payments)

• Can prove the professional purpose

So your transport and accommodation certainly seem to meet these requirements if you are there for professional reasons!