My reconciliation(s) seem to be all messed up. Can I undo all previous bank reconciliations, unlink my bank accounts, and do manual bank reconciliations each month? How?

It's possible to undo bank reconciliation, unlink accounts, and reconcile manually. I'm here to help you through the process, tinalscott.

You can only un-reconcile transactions one at a time. If you need to start over, your accountant can undo the entire period using QuickBooks Online for Accountants. Here's a guide for your accountant on how to undo a client’s reconciliation in QuickBooks Online Accountant. Once done, you can reconcile your accounts once again. 

If you don't have an accountant or prefer to do it yourself, you can manually unreconcile a reconciled statement one by one.

Here are the steps: 

1. Select Chart of accounts from Settings. 
2. Look for the account that has the reconciled transaction and click on View register.
3. Select the transaction to expand the view.
4. Proceed to the checkmark ✔ column, and click the box with the “R” until the box is blank. This removes the transaction from the reconciliation.
5. Click on Save and then close the register. 

Check out this article for more information about unreconciling an individual transaction from a completed reconciliation: Undo or remove transactions from reconciliations in QuickBooks Online. 

Here are the steps that can follow If you'd like to delete your bank account: 

1. Navigate to the Transactions tab, then access Bank transactions.
2. Choose the bank account tile.
3. Click on the pencil  con, then opt for Edit account information.
4. Tick the checkbox for Disconnect this account on save.
5. Select Save and Close.

Once disconnected, transactions awaiting categorization will no longer be visible in the For review tab. Make sure to categorize these transactions before doing so. Here's more information about deleting a bank or credit card account: Disconnect accounts connected to online banking in QuickBooks Online. 

In case you'd encounter errors while reconciling your accounts, here's how you can fix issues at the end of a reconciliation in QuickBooks Online. 

Let me know if you need more information deleting a bank account and reconciling your accounts. I'm always here to answer them for you. Have a great rest of the day!