Every line item can have a class assigned. If you turned on using classes but don't see the column on invoices check the invoice layout in customization, perhaps it is marked hidden
We use classes so it is turned on for my client but when I open an invoice, there is only one class assigned for the entire invoice.
I would offer a screen shot of the blank invoice but it will not load into this message.
Can you explain how you get a class per line on invoices?
@john-pero is right. If you don’t see the Class column on your invoices check the layout of the invoice template. Here’s how:
Once done, you should find the option available for each line item. Refer to this article for more information: Use and customize form templates.
That should get you pointed in the right direction.
Keep me updated on how this goes. I’m always here to help if you need anything else. Have a good one!