Thanks for checking in with us, edb12685.
QuickBooks uses your chart of accounts to organize all your accounting. The opening balance is the starting point for the account you create in your account and it summarizes all past transactions in your real-life account up to the opening balance date. In QBO, we can only upload a spreadsheet to import your accounts and skip manual entry in QuickBooks Online (QBO). From there, you can enter your opening balances for the bank, credit card, and other accounts as stated in Step 5 in the article provided.
You can also enter the old balances as journal entry transactions. However, it would be best to contact your accountant on what posting accounts you'll need to apply. You'll want to check our Intuit Marketplace and look for a third party application that might help you transfer your old balances data to QBO.
To learn more about migrating your Desktop file to QBO, check out these articles:
I'd like to know how you get on after trying the steps, as I want to ensure this is resolved for you. Feel free to reply to this post and I'll get back to you. You have a good one.