1. Login to Unified Reseller Control panel.
2. Click on Account tab
3. Select Orders and Invoices you will get a option to view unpaid invoices.
4. Select the Unpaid invoice and click on Pay Invoice.
5. You can use available 'credit limit' or 'credit memo' to pay the invoice(s). Check the box and click on PAY button.
6. Once the payment will be processed, invoice(s) status will be changed to Closed.