I need to undo " payment received" to resend an invoice. Invoice hasn't been paid, but is marked as paid.

Hello, usermumned2. 

I'd be happy to provide more detailed steps to help you mark your invoice as unpaid. In order to change the status of an invoice to unpaid, you'll need to delete its payment transaction. Here are the steps you can follow: 

1. Log in to your account and navigate to the Sales section.
2. Choose the Invoices and locate the invoice you want to mark as unpaid.
3. Under Action, click the dropdown, tap View/Edit, and select Delete.
4. Click Yes to confirm the deletion of payment.

It's important to note that if you delete a paid invoice, the payment will not be deleted. Instead, the payment will automatically apply to your customer's next invoice.

Managing customer overpayments in QuickBooks Online can be a bit tricky, but with the proper guidance, you can easily track and manage them. Here are some articles that can help you with that:

• Handle a Customer Overpayment in QuickBooks Online
• Record a customer refund or supplier refund in QuickBooks Online
• Manage outstanding balances for customers and suppliers in QuickBooks Online

If you're still having trouble locating the "Mark as delete" option, let me know, and I'll be happy to provide you with additional guidance. Have a great day!