Welcome to the Community, Butler. I can share some information about invoices in QuickBooks Self-Employed (QBSE).
In QuickBooks Self-Employed (QBSE), if an invoice has been marked as paid, there is no direct option to reverse this action. However, you can follow a workaround by deleting the invoice and creating a new one with the correct details. Please note that deleting and recreating the invoice will not impact any online payments that have already been processed.
To delete and recreate the invoice, you can follow these steps:
- Look for the invoice in the Invoices tab.
- Click the drop-down list beside View, then select Delete.
- Select Yes.
I'm adding this screenshot as your visual reference.

Once done, recreate the invoice by clicking the Create Invoice button and entering the same details. Once done, click the Mark as paid button under the Action column.
This article contains all the essential information you need to know about managing invoices: Create invoices in QuickBooks Self-Employed.
You'll need additional guidance and information about hot topics with QuickBooks Self-Employed:
Feel free to leave a comment below if you need help or have questions about managing your invoices in QuickBooks Online. I'll be here to lend a helping hand. Stay safe, and have a productive day.