Good day, @Mike1141.
Let me answer this query for you.
Using the Accountant's Copy feature, the client and accountant should use the same version or year of QuickBooks Desktop (QBDT).
For now, you can still work on the Accountant's Copy using a different version as long as the gap between the versions is just one year, and the accountant has a more recent version. Having said that, importing the accountant's copy from version 2018 is unavailable.
For more information, see the Accountant's copy overview.
Additionally, you can check out this article to know more about file compatibility in QBDT: Company file limitations when upgrading to another product.
Let me know if you need further assistance with this. I'm always around to provide answers and clarifications to your questions. Have a great day ahead and take care.