Note: To change anything besides the invoice amount and/or invoice distribution, simply open the invoice record and make any necessary changes. Be sure to save and close the invoice once the changes have been made. To make changes to the GL distribution of the invoice, follow steps 1-5 below. If you need to delete the invoice, follow steps 1 and 2, and then open the invoice and select File > Delete. 
2. If you would like to reuse the payment number, purge the payment after voiding it*
3. Go to Records > Invoices, and open the invoice record.
4. Make any necessary changes
5. Save and close the invoice record 

*Note: If the “Void and Purge” button is grayed out or if you get the message, “This range does not contain any voided checks that can be purged. You may need to run Post to General Ledger before purging these transactions”,
post the payment reversals to the General Ledger.