Most fields in an existing payable can be modified. However, there are some restrictions.
A payable that is approved, or has a previous payment, can only have the Priority, Due Days, Discount %, and Discount Days modified, and the only priorities available are Immediate, and 2 through 9. If the payable is a debit, Discount %, and Discount Days can never modified.
If a payable has no previous payments and is not approved, then you can change any field, including the payable amounts. An invoice cannot be changed to a debit and vice-versa. In other words, when the payable amount is positive, it must always be positive, and if the payable amount is negative, it must always be negative.
Changing the payable amount actually voids the original invoice, and then creates a new invoice with the new amount. If you were to change the amount of an invoice and then generate the AP Invoice Register report, you would see both the voided invoice and the new invoice. It is important to note that the voiding process and the new payable creation process both generate postings, and that these postings can only be applied to the current GL Period. If the postings of the original payable have already been released and applied to a previous GL period, then you may want to post reversing GL journal entries.
if a payable of 1500.00 is created with control account 11111- and distribution account 44444-, then two AP journal postings are created:
11111- -1500.00
44444- 1500.00
Assume these postings are released, GL period 06 is updated, and GL period 06 is closed. GL period 07 then becomes the current period. If the payable amount is then changed to 1600.00, the void process creates two new postings whose purpose is to cancel out the original postings:
11111- 1500.00
44444- -1500.00
and two new postings for the new amount are created:
11111- -1600.00
44444- 1600.00
Assume that the four new postings above will be released during the next release process, and the current GL period 07 will be updated with those postings. In this case, post to the current GL period a journal entry that will cancel out the postings generated as a result of the void process:
11111- -1500.00
44444- 1500.00
Finally, post to GL period 06 a journal entry that will cancel out the original payable postings:
11111- 1500.00
44444- | -1500.00 |