In a first aspect, the invention provides a system for monitoring and auditing data in one or more spreadsheets. The system comprises a file store within which files containing spreadsheet data can be stored, a database, and monitoring means. The monitoring means is operative to detect changes in spreadsheet data within the file store and to record the changes in the database. Changes in a spreadsheet over time may thus be monitored and recorded. In another aspect the system comprises an entity selector for selecting one or more entities in a spreadsheet, and a tracker for tracking the shift in position of the selected entities between two time points. An offset determinator is arranged to derive one or more offset values from information received from the tracker, the offset values representing the shift in position of the entities in the spreadsheet. An offset applicator applies the offset values to the spreadsheet data before comparing the spreadsheet data with a version of the spreadsheet data at a different time point. Shifting of entities resulting from insertion or deletion of rows and columns or sorting are thus taken into account when comparing spreadsheets. In a further aspect, the invention provides a system for processing and storing spreadsheets. The system comprises a determining unit arranged to determine each unique formula occurring within a spreadsheet, a first store for storing each unique formula, a second store for storing a unique identification for each unique formula, and a replacing unit arranged to replace each formula occurring within the spreadsheet with its corresponding formula identification. More efficient storage of formulas is thus achieved.