A computer-implemented method including: creating, by a computer device, a database record for a user in a computer-based immutable ledger; updating, by the computer device, the database record with a beginning amount of fuel when the user rents a vehicle; receiving, by the computer device, fuel purchase information from a fuel dispenser at a filling station; updating, by the computer device, the database record with the fuel purchase information; updating, by the computer device, the database record with an ending amount of fuel when the user returns the vehicle; determining, by the computer device, an amount of overpayment for fuel by the user; and updating, by the computer device, the database record with a credit based on the determined amount of overpayment.