Enter a deposit manually

Keeping your accounts updated is my priority, @llpadie. That's why I'm here to guide you as to how you can correct the account used for one of your deposits in QuickBooks Online (QBO).

Before we start, can you provide further details of your concern like a screenshot of the display error you have? This is to see where's the exact page you're unable to select Accounts Payable (A/P) when updating the deposit account.

When you make a bank deposit, you're able to choose the account you want to put the money into and the payments and additional funds or fees included. Based on your description of the issue above, you may unable to select the appropriate account because you've already reconciled for that particular month. With this, you can manually remove the deposit transaction from reconciliations to correct its account details. To do this, here's how:

1. Go to  the Accounting menu.
2. Select the Chart of accounts tab.
3. Find the account that has the reconciled transaction. Then select View register.
4. Locate the deposit transaction. If the transaction is reconciled, you’ll see an “R” in the checkmark ✔ column.
5. Select the transaction to expand the view.
6. In the checkmark ✔ column, select the box with the “R” until the box is blank. This removes the transaction from the reconciliation.
7. Select Save. 
8. Close the account register.

Once you're done, go ahead and update the deposit's account details. Then, reconcile the account again to make sure it matches your bank statement and detect any possible errors. You can refer to this article for the complete guide: Reconcile an account in QuickBooks Online.

Also, to further guide you in doing or fixing a reconciliation in QBO, I'd recommend checking out this article: Learn the reconcile workflow in QuickBooks.

Keep me posted in the comments if you have other concerns about managing your deposit transactions in QBO. I'll gladly help. Take care, and I wish you continued success, @llpadie