Adjusting the relevant stock records
Sage 50 Accounts uses the First In First Out (FIFO) system. This means you can't simply post an Adjustment Out (AO) for the quantity that has been incorrectly delivered, because the AO removes the oldest stock, not the stock that you've just delivered.
Read about the exact method in our adjust stock records after deleting or reversing a purchase order article.
To correct the purchase invoice
If the order has been updated as well as delivered, the purchase invoice may also be incorrect. To correct this, delete the original invoice using the Corrections option then update the new or amended purchase order to re-post the invoice.