@Eve2019 

Invoicing your customer for shipping is income, not COGS.  If you were to classify it as COGS, it would decrease your COGS when invoicing a customer and you don't want that.  I was a controller for a few retail companies for many years and we had FI (sub-category of COGS), FO as an expense and S&H as a sub-category of income.  That way, you can track incoming freight costs to make sure you're getting adequate markup to cover the cost of FI.  And, you can see your FO costs relative to your S&H income to see if you're able to make your S&H more competitive.  Hope that helps.