QuickBooks company file extension can vary depending on the version of QuickBooks you are using. QuickBooks company file extension is applicable to all files. It is important to know all the necessary file extensions and their usages. Visit QA Solved.com to understand all the file extensions in detail. Additionally, there is a special focus on QuickBooks back up file extension. Call now at QuickBooks support number 1-877-263-2742 to understand the process in detail.