I'm trying to create our first invoices, but I'm struggling with it.

We need to add different comments on our invoice items in order to keep them apart from another. For example, I need to add product A twice, once for customer 1 and once for customer 2. 

I also have to add the period of performance, which isn't always the previous month. Does anyone have an idea on how to do this?

I'm using Odoo 10 Community version.

Thanks!

Marco