Good day, lindycooper.
The Undo option is only available in QuickBooks Online Accountant. I'd recommend inviting your accountant to your company, and let them undo the reconciliation period at once.
- Click the Gear icon in the upper-right corner, and select Manage Users.
- Go to the Accounting firms tab, enter the accountant's email and click the Invite button.
- Click Save.
- Let your accountant undo the entire reconciliation.
Otherwise, you'll need to undo the reconciled transactions one at a time. You can use this article for reference: Undo and remove transactions from reconciliations in QuickBooks Online.
For some "How do I" steps in QuickBooks Online, you can always visit our Help Articles page for reference.
If you have other questions or need assistance with anything else in QuickBooks, please update me by clicking the Reply button below. I'll be more than happy to help.