This depends on your employer's policy, the policy of the sponsor of the research study you are working on, and/or the policy of the trust where the research takes place, and your previous experience.
The frequency of GCP training is not specified in the regulations. However, it is recommended that training is given at intervals appropriate to ensure staff maintain awareness of the current UK and EU regulations. If you have just participated in training and a relevant regulatory change is made, you will need to be informed of these changes and understand their implications for your practice. The University recommends that certificates are renewed every three years.