Locate the invoice with Due status to which you want to apply payment manually and click its ID.
The invoice details will appear below the record of the invoice you are viewing. The other option is to click on the magnifying glass icon in the Available Operations column to view the invoice details.
Click the Quick Manual Payment link in the Tools section of the page.
Set the following:
Choose Billing Account. Select the billing account you want to use for this payment in the drop down menu.
Payment Method. Select the payment method you want to use for this payment in the drop down menu.
Check Number. If payment is being made by check, enter the check number.
Apply Payment To. SelectEntire Invoice or Selected Line Items. If you choose the Selected Line Items option, it will list the line items available for this invoice. Choose accordingly.
Amount of Payment. Enter the payment amount that you are applying to this invoice.
Payment Comments. Enter comments according to your specific needs.