Normally if you need to modify an invoice, you will update it in the system it was created in. So from WinCopy or WinServe Plus you just update the invoice and a credit memo is automatically generated and the updated invoice is also created. You will notice the update in your accounting system as the credit memo and invoice flow in once you import sales. The purge will remove the original invoice and the credit memo so only the updated invoice will remain on the account.
Now to discuss the not normal.
If you receive payment for an invoice and partially apply it to the invoice, the system should block you from further updates to the invoice. So if you want to cut down the invoice to the amount received, update the invoice, import the sales and run the purge, then apply the payment to the corrected account.
If you receive full payment for the invoice and you figure out you over billed the customer after the check is entered, you can't modify the invoice. If you have our unpurge function, you can unpurge the payment and invoice, then void the payment and modify the invoice then reenter the payment as needed.
If you receive full payment and the invoice is purged, and you figure out it was overbilled, you can create a credit memo on the account, but you must apply that credit memo to an invoice that is more than the credit amount (or you can enter multiple credit memos to make the full amount) and apply them to the current invoices that remain unpaid.
The invoice entry screen in A/R is used to enter the credit memo:
Select the account, a reference number and other reference information and check the this is a credit memo box.
You then enter the distribution of credits in the income account section:
You can enter negative amounts in the amount field as needed. The income account is used to reduce the amount of income for that invoice income account which will show on the month end report.
Once you complete your entries, please click the post invoice to add that credit memo to the account that needs to be updated.
If you full pay an invoice, run the purge to clean up the account.