How do I endorse an invoice price?

You should put this in the endorsement column next to the item in question.

The price should not include VAT, as there is no process in place to calculate and deduct VAT from the amount endorsed.
 
If the item is an unlicensed special not in Part VIIIB of the Drug Tariff, the price endorsed should be less any discount or rebate; the pack size should also be included.