Hi @alina11,
I appreciate you for getting back to us here in the Community. Allow me to step in and provide some information to your questions about reconciliation in QuickBooks.
When reconciling an account, you can include journal entries from the prior years. However, the recommended method to reconcile them is one year at a time.
For transactions older than the opening balance in QuickBooks, I suggest checking out this link: Enter an adjusting entry for a reconciliation in QuickBooks Online.
Since you've been advised to add the data from year-end, it would be best to reach out to your accountant again. They'll be able to guide you further with how to handle them in QuickBooks and ensure your books are error-free.
For additional reference, you can use the following article to fix a reconciliation, as well as how to undo reconciled transactions in QuickBooks: Learn the reconcile workflow in QuickBooks.
Drop me a comment below if you have additional questions while performing the reconciliation process. I'll be happy to help you some more.
