You'll have to edit this non-inventory part and tick the checkbox that will show you a field for Cost and Sales Price.
- Go to the Lists menu, select Item List.
- Look for the non-inventory part in question, then double-click it.
- Tick the checkbox labeled This item is used in assemblies or purchased for a specific customer:job.
- Fill up the fields with the necessary information.
- Hit OK when done.
With this, your purchase orders with the non-inventory item in question will auto-fill with the amount you entered on the Cost field. When you create an invoice with it, it will auto-fill with the amount you entered on the Sales Price field.
Learn how to manage your items in your Item List with this article: Add, edit, and delete items. It has a list of frequently asked questions, along with its answers.
Let me know if you have other questions by leaving a comment below. I'll be sure to get back to you.