An FEI credential card or passport is always valid for four years. On the front of the FEI section you can see how long the passport is valid until. If it has already been renewed once, you will find yellow seals on the back of the FEI section. After that (or rather just before the expiration of the passport) you have to renew it, unless the horse is no longer competing at international competitions.
The KNHS can renew the FEI passport for you. Send the FEI passport together with the completed form "application form FEI passport" to the KNHS. In the KNHS price list you can find the costs for an extension of a FEI passport. The costs for horses and ponies are different.
NOTE: Do you want to visit the KNHS office to have your FEI passport changed? Then you must first make an appointment. Make your appointment by sending an e-mail to firstname.lastname@example.org.