In one embodiment, a method includes receiving, by a payment service system (PSS), a payment request from a payment application executing on a device of a sender. The payment request includes a recipient identifier corresponding to a recipient. The sender and recipient have financial accounts associated with the PSS. The method includes determining a similarity score based on a comparison of contact records associated with the device of the sender and contact records associated with a device of the recipient. The method includes, responsive to determining that the similarity score does not satisfy a threshold similarity score, transmitting a confirmation request to the device of the sender to confirm an identity of the recipient. The method includes receiving, from the device of the sender, an approval response to the confirmation request. The method includes, authorizing a payment transaction associated with the payment request based on the approval response.