Register once, no card. The check and its findings are free. The exports — Home Assistant config, handover pack — are free during trial.
Your account keeps a list of the checks you have run, with each project's size and complexity — the number of addresses, devices and functions. That is a record of your work, not your client's building, and it is there so you can find a project again later.
Your uploaded file is a separate choice, made each time you upload. You can delete your account and everything recorded under it at any time.