A computer-implemented technique is described for using an automation tool to facilitate the preparation of a summary document, such as an expense report. In a first data path, a receipt-processing component generates receipt items based on images of physical receipts that a user captures using a camera. In a second data path, one or more transaction-processing systems forward transaction items to the automation tool upon their capture; the transaction items correspond to electronic records of transactions made by the user. The technique then generates a set of receipt-transaction (R-T) pairings by matching pairs of receipt items and transaction items that describe the same respective transactions. The technique then uses context information to supplement the R-T pairings, and generates a summary document that summarizes transactions made by the user based on the supplemented R-T pairings. In one case, the context information corresponds to calendar information specified in a user's electronic calendar.