Is there a way to fix a supplier deposit that has been coded to the wrong account and has been reconciled?

Hello service-vpnz-co-,

Thanks for dropping by the Community page. Allow me to provide some information about bank reconciliation in QuickBooks Online.

If you've allocated the transaction to an incorrect bank account and reconciled them, you'll have to undo the reconciliation to correct the  balance of each account. For small business accounts, we'll have to manually unreconcile each transaction to undo the reconciliation. Here's how to unreconcile the  bank:

Here's how:

1. Go to Transactions tab.
2. Select Chart of Accounts.
3. Choose the account you’re working on, and click on Account history or View Register.
4. Select the transactions you want to unreconcile.
5. Keep on clicking the R status until it shows blank or cleared (C).
6. Click on Save.
7. Choose Yes in the confirmation window.

Repeat the same process to the other bank account in question. Furthermore, if you have an accountant that uses QuickBooks Online for Accountants, you can add them as an accountant user so they can bulk undo the reconciliation period the transaction in question. 

You can refer to this link to learn more about: Undo or remove transactions from reconciliations in QuickBooks Online.

Post again in the Community if you have further QuickBooks Online concerns.