Hello ezgi,
Welcome to the Community - thank you for your question!
You can run reports on specific classes by going to the cog wheel in the top right hand corner, and clicking All Lists. Once there, if you select Classes you will be given an option to run report next to the class you would like. On this report, you can then customise through the top right hand corner so that it only shows invoices through the filter option and 'transaction type'.
Thanks,
Talia
