A CBT Certificate is valid for 2 years. You should keep your CBT in a safe place but if you have lost your certificate, a duplicate can be obtained from the training centre you attended (or the DSA if they are no longer trading).
Do remember that if you are riding on a CBT the maximum size of motorcycle you can ride is 125cc (or 50cc if you're aged 16). You are not permitted to ride a motorcycle over 125cc that has had the power output restricted.
