Peatix provides receipt as a proof of payment. 

After an order is complete, the buyer can access the receipt from the Ticket Purchase History tab or the order confirmation email. 

Please see the attendee help page for more details on how the buyer can access the receipt.

Peatix doesn't issue proof of payment in format other than receipt.

If the buyer needs a proof of payment in the format other than the receipt provided by Peatix,  please issue the proof of payment at your own discretion.