The Condense Data utility in QuickBooks Desktop streamlines your company data file by removing unused list elements and condensing closed transactions into summary journal entries. These changes made to your company file affect your accounts in exactly the same way as the detailed transactions. Read through this article to know more about condensing; its limitations, how it is done, and what to do before, during, and after the process.

Note: If you are having performance did  issues, the Condense Data utility is your last option to try to improve performance.

What you need to know about Condensing: