How do I show cost of sales by the sales invoice?

You've come to the right place, @carla9. 

You can run the Profit and Loss Detail report. This report allows you to drill down to cost of sales by invoice with ease.

Here's how:

1. Go to the Reports menu.
2. In the Find report by name field, type in "Profit and Loss Detail," and press Enter.
3. Modify the reporting period.
4. Click Run report.

It's also a great idea to modify your report to focus on the details that matter the most, check out these links: 

• Customize reports in QuickBooks Online
• Reports included in your QuickBooks Online subscription

If there's anything else that I can help you with, please let me know in the comment section down below. I'll be always around ready to help.