FET is a manufactures tax. It does not make any difference what you paid for your components, (e.g. sales tax and/or FET) you still need to collect/owe 10% of the sale at the manufactures/wholesale level. In order to deduct FET already paid, you need a way to prove this, like an invoice with the FET stated on the invoice. I sell at the wholesale level and I add the FET at the bottom of the invoice, just like you would sales tax. Hagens, Worth Company, Shorty Hook Sales all invoice the same way. Shortys is not a manufacturer but can sell without FET providing that you have a Form 637 on file with them. It is not to be collected at the retail level and thats a whole different discusion.