If you just do not want to track inventory, then use non-inventory items, set the non-inventory item screen to being used in an assembly or for resale, and set the expense account to COGS, and the income account to Sales. BUT only buy in the quantity you are selling. QB will send the total cost of the purchase to the COGS account when the item is bought, so only buy what you are going to sell immediately. QB does NOT stock non-inventory items.

If you have strictly a service based business then COGS gets renamed (usually) to COS (Cost of Sales). Things like merchant account fees that are directly related to the sale often go in this account. Directly related is the key.

When you file the IRS paperwork COS is just an expense account. COGS has a seperate area for calculations in the IRS filing where you show beginning inventory, purchases, ending inventory to calculate cost (at least on the Form 1065 I file).