Thank you for that idea.

When creating an sales invoice, there are two sets of entries created:

a. Dr. Accounts Receivable; Cr. Sales

b. Dr. Cost of goods sold; Cr. Inventory

In the above entries, you don't need the first. In the second entry, you need to convert the Cost of goods sold to Fixed Assets. Hence, I suggest that in the invoice, set the amount to zero so you don't create unnecessary amounts for Accounts Receivable and Sales. A journal entry will still be needed which reclassifies the Cost of goods sold to Fixed Asset, thus, Debit Fixed Asset and Credit Cost of goods sold

Cheers!