A computer system can implement a network transaction service by monitoring location data from a computing device of a user to confirm that the user is located at a merchant location, receiving transaction data from a point-of-sale terminal of the merchant location, and confirming that the user has left the merchant location based on the location data. The computer system may then automatically execute a transfer operation to fund the transaction using a shared funding account of the network transaction service such that no direct payment interaction is made between the user and the merchant.