Short answer: Fingerprints on the card can be changed after issue. How depends on how the card was enrolled in the first place: self-enrolled cards are managed in the IDEX Card app, station-issued cards at the issuance desk. Adding or replacing a fingerprint does not affect the keys and credentials on the card. Deleting all fingerprints has a different consequence, described below.
Self-enrolled cards: in the app
The app has a dedicated delete function: scan the card, open the enrolled fingerprint and remove it, then enrol again the same way as the original enrolment. Your PIN is required, so the card cannot be re-enrolled by someone else without it.
On some card models, fingerprints can only be deleted all together rather than one at a time – the app tells you when that is the case, so read the prompt before confirming.
See: Set your PIN.
Station-issued cards: at the desk
The user returns to the issuance desk, and an operator verifies their identity before changing the enrolment. The verification step is what keeps the binding between person and card trustworthy. Cards issued at the station cannot be re-enrolled from the app; they are managed at the station.
See: Operating the enrolment station.
What changing a fingerprint affects
Nothing else on the card. Door credentials and registered passkeys are stored separately from the fingerprints and continue to work as before – the fingerprint decides who can use them, not whether they exist.
Deleting all fingerprints
A card with no enrolled fingerprints may still carry working credentials, and depending on how your access control system is configured, it can then open doors without any fingerprint check. For this reason, deleting all fingerprints is not recommended. To take a card out of service, revoke it instead. See: Lost or stolen card: revoke and replace.