had that scenario this morning - but they don't use inventory and they import their invoices daily from another system. So I just opened the import file, switched the signs, imported as negative which created adjustments (but I was going into AR Invoice entry, not SO), posted with the bad date and then reimported with the good date. The idea is the same with SO Invoice entry, just a bit more complicated - if the system will recoginize the same invoice # and customer (like in AR invoice entry) and just create the negative adjustments rather than creating new credit memos that apply to the original invoice that might be easier