In the future you should make sure the amount on the po reciever agrees with the  invoice.  You could book the receiver when you get the invoice.  They can be recorded at the same time.  There is an adjustment process in Sage 300 that will automatically adjust all items that have cost but no quantity.

Dana 

Doesn't really answer my question and where is this adjustment feature?

It's under Inventory Control, I/C Transactions, Adjustments.  Under Inventory Control, I/C Periodic Processing, Process Adjustments is the function that will allow you to create an adjustment batch for items with no quantity and residual costs.