How do invitations work?
Under Scan credit → Invite someone you find your own link. Share it however you like: in a message, by email or on social media.
You both receive free scans once the person you invite confirms their first document; the page shows how many, next to your link. Signing up is not enough: the scans arrive when they have uploaded a document and confirmed what was read from it. That way an invitation rewards real use, not an empty account. Each invitation is rewarded once.
Under your link you see each invitation with its date and where it stands: waiting for a first document, or rewarded. Carnoat never shows who signed up through your link, and never tells the person you invited who you are, because links are often shared publicly. You are told in Carnoat when someone signs up through your link, and again when the scans arrive, by email too unless you switched that off under Settings → Notifications.
The number of rewarded invitations per year is limited. Once you reach it, the page says so: your link still works, but neither of you receives scans for new invitations until a year has passed since the earliest rewarded one.
Did you follow someone's link? The sign-up page says so, and you receive the scans once you confirm your first document. Follow the link before you create your account: an invitation can't be added afterwards. If you don't see Invite someone, invitations are not offered at the moment.