How to Close 2 years Old Open PO

There are some two year old open service PO

Now customer wants to close the PO

The invoices has been posted for lower amount than the PO or some invoice has been posted as non-PO.

Now customer want to close all such PO

But customer don't want the accounting entries in current fiscal

What should be the solution in above case

Please explain both scenarios.. 1 want to book any cost against PO and 2. Dont want to book any cost against PO

Please guide