You can easily access and download the invoices issued by RSVP from your Profile Settings section of the admin.
Once you are logged in and on the Profile Settings section, scroll down to the Invoices and Billing section.
Note: Please be sure to have the accurate billing information entered (i.e. company name and registration number). See how to do so at https://intercom.help/rsvp-pop-up/en/articles/3376505-welcome-to-rsvp.