My dad owns a small construction business. I am not sure how to list his materials. He bids jobs, if the customer is is happy they pay for a portion of the job upfront. He then uses that money to buy their materials for the job to be completed. He buys his own nails, screws, rags, etc. I understand that those need to be categorized as an expense to him. I am unsure how to list to others, if it would classify as a COGS or not?