You may have businesses or installers that you have worked with many times and are confident in their delivery. If the contract is between yourself and your customer, then you have ultimate responsibility for the works. If, however, the sub-contractor will enter into a separate contract with the client, then this sub-contractor must also be TrustMark registered. You can find out more information in the TrustMark Code of Conduct and Customer Charter.
When lodging work undertaken by a sub-contractor their TrustMark license number must be provided, a check is undertaken to ensure that the sub-contractor was TrustMark registered for the work type when the work was undertaken.