A invoice says paid but it hasn't been. How can I remove the paid part from it and resend.

Hello, I’ve created an invoice for a client but haven’t sent it yet. The system is now telling me it’s been paid but it hasn’t as I haven’t sent it yet? 
I can’t seem to undo? 

Your client may have an open balance, Db1986. That's why the system marked the invoice as paid even though you haven't sent it yet.

We can review the customer's profile to check if a credit balance exists.

Here's how:

1. Go to the Sales tab.
2. Click one customer under the Customer section.
3. Navigate to the Summary section; you'll see the Open Balance available.

Once verified, follow these steps to undo or delete the credit payment that was applied to your invoice.

1. Select an invoice with the applied credits and click on View/Edit.

2. Click the Blue Hyperlink of the credit applied, then select the date. The payment transaction will open.

3. Choose More, then Delete.

4. Click on Yes, to confirm.

To avoid auto-applied credits in the future, we can turn off the Automatically applied credits from the Accounts and Settings. See this page for your guide: Create and apply credit notes or delayed credits in QuickBooks Online.

I've added this link to guide you on setting up automatic or manual reminders for overdue invoices: Send invoice reminders automatically or manually in QuickBooks Online.

Please don't hesitate to post a reply if you need further assistance regarding QBO-related topics.