A subcontractor's insurance is bought twice over: once for the risk the work actually carries, and once for the clause in somebody else's contract. The second purchase is the one that stops the job, because a site will refuse entry over a missing certificate long before anybody assesses whether the limit was sensible.
Labour only or bona fide, and why the label matters
Insurers divide subcontractors in two. A labour only subcontractor works under your direction, with your materials and often your tools, and in insurance terms behaves like an employee: their wages usually count towards your employers' liability rating and their acts fall to your policy. A bona fide subcontractor runs their own business, brings their own materials and carries their own insurance, and is rated differently. Declaring one as the other is the single most common cause of a premium adjustment at audit.
The certificate the main contractor wants, and when
Main contractors usually ask for evidence before you start and again at renewal, and the request is specific: the insured name matching the entity on the subcontract, the limit at or above the clause, and the period covering the works. A certificate in the trading name when the contract is with the limited company is a common rejection. Where a contract asks for the main contractor's interest to be noted, that is a change to the policy and needs to go to the insurer rather than being assumed.
Your own subcontractors, and the chain that follows
A subcontractor who subcontracts becomes a main contractor for that link, with the same duty to check certificates. Insurers ask for those records at audit, and a contractor who cannot produce them normally finds the wages of those people loaded onto their own employers' liability rating. Keeping a copy of each certificate with its expiry date is dull administration that pays for itself the first time a wage roll declaration is challenged.
Gaps that appear at the end of a job
Two gaps recur. The first is the period after practical completion, when defects work brings you back to a site nobody has told your insurer about. The second is the run off after a business stops trading, because a liability claim can arrive long after the last invoice. Public liability responds on the date the injury or damage happens, so cover that lapses leaves the old work unprotected even though the work itself was done while insured.
Questions people ask about subcontractor insurance
Do I need my own insurance if I am a labour only subcontractor?
The main contractor's policy usually answers for your work, but they will still often require your own public liability, and you need employers' liability if you have staff of your own.
Why does a main contractor want to be noted on my policy?
So they have a route to the insurer rather than only to you. It is a change to the policy, so it has to be requested from the insurer rather than assumed.
What happens at an insurance audit?
The insurer checks declared wages and subcontractor certificates against what actually happened. Missing certificates usually mean those payments are rated as your own wage roll.