If you want to check your commission's invoice for a specific appointment, log into your profile and click on 'Calendar,' then select the date and service you are interested in.
Once you click on the appointment, you will see the summary page and also find the related document, which you can download as a pdf.
You will also find the same documents by accessing the 'Transfers' section, selecting the relevant payout and then the specific appointment.
If you want to download all the invoices for an entire year, go to 'Invoices' and you will find the specific feature.