Hello Danny Gonzalez,

If you are using slandered odoo import feature then you have to import products first then you can give external ids of those products in your invoice's csv or excel file or we can create the script which checks if product exist or not. If the [roduct does not exist we create it first and then create invoice.

So as per your requirement you can create the xmlrpc or odoorpc script to create product automatically while importing for csv of invoice.

Hope it will help you.

Thanks & Regards,
Email: odoo@aktivsoftware.com
Skype: kalpeshmaheshwari