We can run a different report to see the markup per item, @tom210. It's my pleasure to walk you through pulling up and customizing it.

Go to the Reports menu, select Sales by Product/Service Detail Report, and click the Customize button at the upper right corner. On the Rows/Columns, tick the Product/Service and filter by Transaction Type. It will show the markup per item according to invoices.

In addition, here's an article to learn more about customizing an invoice template: Customize invoices, estimates, and sales receipts in QuickBooks Online.

Lastly, I've also included this helpful guide for ideas about how you can receive payments from your customers: Record invoice payments in QuickBooks Online.

Keep me updated in the comments if you have any other questions. I'll be here to lend a hand.