The QuickBooks Condense Data utility can be used to shrink the size of your QB Desktop company file by removing old transactions and replacing them with summary entries, and removing inactive lists. It can improve performance for large files or those nearing list limits. However, it is irreversible, so it is advised to make a backup file before using the Condense Data Utility. The process also might or might not affect the size of your company file. If your company file is damaged, it’s recommended to use the file doctor instead.