A method of intermediating transactions includes, at an intermediation server: receiving invoice data defining a price payable to a vendor for supplying a product to a customer; extracting, from the invoice data, a vendor identifier corresponding to the vendor; determining, in association with the invoice data, a customer identifier corresponding to the customer; retrieving a payer identifier corresponding to a payer associated with the customer; retrieving, based on at least the payer identifier, a transaction policy; according to the retrieved transaction policy, allocating an eligible portion of the price to the payer identifier, and allocating a remaining portion of the price to the customer identifier; and generating and transmitting payment data for initiating a payment of the eligible portion from the payer to the vendor.