If you are a gas operative or engineer, you must have a valid and current certificate of competence for working on any domestic gas appliance. This is a legal requirement.
You can achieve this by undertaking the relevant appliance Accredited Certification Scheme (ACS) assessment via this course.
To take this course, you must hold a valid and current CCN1 Gas Core Safety Certificate, or the equivalent NVQ Level 2 or Diploma Level 3 in Gas Installation and Maintenance.