Hi there, SSS00.
Thank you for posting here in the QuickBooks Community.
Currently, QuickBooks doesn't allow you to convert a 2018 file to a 2019 file.
I suggest to ask a copy of the file from your accountant for 2019 and import it to your company. You'll need to have a the same version to allow the import.
Here's how to to import Accountant's copy:
2. Select the File menu, then select Send Company File.
3. Choose Accountant's Copy, then select Client Activities.
4. Select Import Accountant's Changes from File if the file is saved on your computer. Choose Import Accountant’s Changes from Web if you are using Accountant's Copy File Transfer.
5. Review the Accountant's Changes and make sure that it does not have a problem with the work you've done.
6. To enter the changes to your file, select Incorporate Accountant's Changes or Close if you do not want to import the changes.
7. To close all windows, Select OK. Click OK to create a backup.
8. Select OK to proceed then Close.
9. Click Yes if you want to update the closing date and password.
Please check this article for more information and the uses about the Accountant's Copy feature in QBDT: Use the Accountant's Copy.
Please know that you're always welcome to post if you have any other concerns. Wishing you and your business continued success.