Hi Jim,
This is by design. LIFO/FIFO is an exact receipt cost of that PO line item's quantity and gets written to the invlifofifocost table at the time of receipt with cost and quantity. Unlike average cost (invcost table), which will accept invoice cost adjustments, Maximo sets the cost at time of receipt. If the invoice cost is different from the PO, you need to return the items, revise the PO with the new cost and re-receive the items. If any of the items were already issued you will only be able to return the items left from that receipt line quantity. When invoicing the line at different cost, you have a choice of putting the difference against the invoice variance account associated with the storeroom (leaving the cost against those items from the original cost on the PO line) or following the return/PO revision process above. You cannot change the cost of a LIFO/FIFO through the inventory or invoice application, on the PO line and receipt.
Hope this helps!
Gina Leonard
Principal Consultant
Aquitas Solutions