Hi Eli, thanks for the pointers.
I checked out the note:
2074291 - Error Mess. FMCF101 / FMCF320 - Automatic carryforward.
However, I'm afraid all my invoices will be automatically carried forward if I apply this note. Isn't there a way to authorize a one time carry forward without implementing a permanent note?
A colleague suggested I create an invoice in 2016 to use all the budget up, then modify the existing sales order (ME23N) in 2017 and then create an invoice for the latter amount in 2017. But that's not exactly the test case I'm suppose to do.
Any hints?