Accounting for shortfall or extras goods from vendor

Accounting for shortfall or extras goods from vendor

Hi everyone. How do we actually account for missing or extra goods from the vendors? Let say the purchase order consists of 100 bags and the vendor sent 120 bags. Since we are unable to change the qty in the received order, is it recommended to just receive 100 bags and then do an inventory adjustment to the qty of the bags? Am i right to say the COGS for the bags will automatically decrease?