Posting an adjustment Invoice

Hi MM Gurus,

I might probably asking you a silly & pretty easy question.

For the PO, the GR qty & IR qty is same but the amount differs. Now I am looking

to post a second invoice for the difference amount.(I haven't checked into details yet as I know the system is configured to block them anyway but the user says that they got few of them)

The options I got are:

A) Post an adjustment invoice for the difference amount (if I could??)

B) Reverse the existing Invoice and create a new one.

C) Raise a credit note for the difference amount.

The first one would be easy neverthless!!

Thanks in advance for your solutions.

Regards,

Madan