@Suitestallion I mean so for your scenario then what happened (and afterwards)? Did the vendor really receive payment, did they receive this payment in full, did they refund you, was this input an error on your team's behalf, and you needed to perhaps void it?

sorry it was an invoice not a bill

I'm not an accountant, and what you're saying can affect it so I'd talk to your business user to really grab the requirements especially on when it's SUPPOSED to post; Since you can unlock previous periods to adjust or you can adjust the current period in the current FY to reduce revenue based on their refund this year (as example) You must figure out when and why the journal happens, and this will give you better idea to design it.

Yes, I know we can re open the period but they don't want to reopen the period, so that's off the table, so that is why I was thinking of issuing credit memo and creating the new invoice.

It'll depend on the incorrect amount of bill and how your client is willing deal with is, and if the bill is paid, i dont think this is a simple situation since the trigger point can have multiple incomes and outcomes

Was the Invoice paid in full? If yes - was the payment/customer deposit the wrong amount too?