Does CIS apply to plumbers and heating engineers?

Does CIS apply to plumbers and heating engineers? Yes, for installing a whole heating, water or sanitation system and for fitting kitchens and bathrooms. As of October 2026, HMRC's manual treats a boiler replacement, an extra radiator, repairs and servicing as outside CIS on their own. Not on its own. HMRC's manual says replacing even a major part such as a central heating boiler is not installing a heating system, so it is outside CIS unless the contract also includes construction work. Yes. HMRC's manual lists kitchen and bathroom fitting as construction work, and CIS 340 includes installing and repairing kitchens and bathrooms. Replacing a single item such as a tap or wash basin on its own is still treated as a system repair, outside CIS. No. CIS 340 lists the repair, servicing and maintenance of heating systems among the operations excluded from the scheme. Read the full answer, with every source, at rightotax.co.uk.