Mobility grants can be spent however you like: rent, plane tickets, visa fees, course materials... there’s no rule specifying what you can pay for with each grant. For this reason, you don’t need to keep receipts for payments made or send proof of payment to the Erasmus office.
The only exception is certain types of grants for students with fewer opportunities, but in these cases, the Erasmus Office staff will provide you with all the necessary instructions.
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