Hi there, satC.
Welcome to the QuickBooks Community. Let me discuss how your company file works in QuickBooks Desktop. Then, ensure you can achieve your goal by following the information below.
If you're trying to downgrade your company file from an older version, this is currently unavailable. That said, you're unable to use the 2021 version file in 2018, 2019, and 2020. You can only upgrade your file from an older to a newer version of QuickBooks. This is to avoid any issues and damage to data in your company file.
However, and as mentioned by Fiat, the exception to the rule shared above is to use QuickBooks Desktop Accountant and work in an Accountant's Copy. That said, you can purchase a one-time license for QBDT 2021 Accountant to achieve the process. For more information, you can open this article: Company file compatibility with QuickBooks Desktop when upgrading.
If you mean to access the older version of your QuickBooks, I suggest using our QuickBooks trial version. This will allow you to view and restore your old backup. Beforehand, make sure the file is compatible and your computer meets the system requirements. This helps avoid any problems and errors.
Lastly, you may refer to this article to see various details about the discontinuation policy: QuickBooks Desktop service discontinuation policy. This also provides some answers to frequently asked questions regarding the older QuickBooks versions.
Please fill me in if there's anything else I can do to help you access and manage your QBDT. You can click the Reply button below to add your response. Keep safe always, satC.
