I would like to hide a line item on a tax invoice.

We work much like the car repair industry.

I invoice out the total service charge in one line item however I have inventory items related to the total charge and if not invoiced individually out it throws my inventory numbers out and it doesn't match actual stock on hand.

I would like to have a line item on the invoice for the inventory item at R0.00 cost for the purpose of reducing this inventory item but I do not want it to show on my customers invoice.

Please can someone assist in telling me how this could be achieved?