What is the difference between cost of sales and cost of goods sold and which should I use to track stock?

Welcome to the Community, @elizabeth11.

There is almost no difference between the two. The terms are typically used interchangeably in accounting.

The Cost of Sales and Cost of Goods sold both tracks how much it costs a business to produce a good or service to customers. The latter represents those goods that were taken off of the Balance Sheet as inventory and expensed as Goods Sold. Other expenses such as shipping of the product can be considered a Cost of Sale.

I recommend consulting your accountant for help in selecting which to use in tracking stocks. For reference, check out these articles: 

• Set up Stock tracking. 
• Impacts of stock tracking on balance sheet and profit & loss reports.

That should answer your concern for today.

Let me know if you need anything else. I’m always here to keep helping. Take care!