Thanks for getting in touch with the Community, Dewey1970.

If you're referring to an invoice that's partially paid and has a Paid status, it can be closed by going to your Receive payment screen and adding the final payment to it.

Here's how:
 

1. In your left navigation bar, use the + New button and click Receive payment.
2. From your Customer drop-down list, choose a customer.
3. Use the Payment method drop-down to pick a payment method.
4. Specify which account you put your payment into with the Deposit to drop-down.
5. Enter an amount in your Amount received field.
6. From the Outstanding Transactions section, find an invoice you're working with and tick its checkbox.
7. Specify a Reference no. and Memo if necessary.
8. Select Save and close.

I've also included a detailed resource about closing invoices which may come in handy moving forward: Record invoice payments

Please feel welcome to send a reply if there's any additional questions. Have a great Wednesday!