Rentcars does not issue an invoice or receipt related to vehicle rentals. According to the applicable local legislation, vehicle rental is not considered a provision of services for tax purposes, and therefore issuing an invoice is not mandatory for this type of contract.
However, there is no need to worry. As proof of payment, you may use your reservation confirmation voucher. In addition, the rental agreement, which is signed at the time of vehicle pick-up, can also be requested from the rental company and serves as proof of your booking.