You can prove to any merchant that a certain transfer has been performed successfully, by downloading the transfer statement.
Via website: go to Transfers > List of Transfers or Accounts and Cards > Account Statement, choose the needed transfer and print out or save the transfer details in PDF.
Mobile app: on the main screen > click on the performed transfer > Get transaction statement.
Provide this statement to the recipient of the transfer. Paysera account statements are equal to bank statements.