2 invoices for same order were inadvertently created. Customer pays 1st invoice. 2nd invoice was sent out. Record of 1st invoice was voided. Can I swap records?

I'm glad you ask about this, pbares-gmail-com.

Voided invoice can't be undone. You'll want to recreate the first invoice and apply the payment to it. Then, you can void the second invoice.

To recreate the invoice:

1. Go to the +New icon.
2. Choose Invoice.
3. Fill in the necessary information.
4. Click Save and close.

To apply payments to the invoice, here's what you'll need to do:

1. Go to the +New and under Customers choose Receive Payment.
2. Select the customer who paid you in the Choose a customer field.
3. Enter the date you were paid and the necessary information.
4. Click Save and close.

In case you need a handy reference on voiding invoices, check out this article: Void or delete transactions in QuickBooks Online.

If you don't know the exact information, you can check the Audit Log. To do that:

1. Go to the Gear icon and select Audit Log.
2. Select Filter.
3. Use the fields on the Filter panel to choose the appropriate User, Date, or Events filter to narrow the results.
4. Click Apply.

Learn more about using the Audit Log Feature through this article: Use the audit log in QuickBooks Online.

You might also want to check out this article for more tips on how to customize your templates including estimates in QBO: Customize invoices, estimates, and sales receipts in QuickBooks Online.

The Community will always have your back if you need anything else in running your business in QuickBooks Online. Have a good one.