How to write down Parts Stock

Create a purchase ledger account called "PARTS STOCK WRITE DOWN" - then go into Parts > Goods In > Enter the part number and the quantity to return as a negative quantity > press "ADD" then repeat the process until finished (all parts wanting to be written down have been entered) - then press "COMPLETE"

Once done, goods the parts back in to stock - at the written down value - ensure this is done to the same account created above (PARTS STOCK WRITE DOWN)

Then the difference can be written off via the account created above, by posting a zero invoice.