Confirm the builder's legal trading identity, check any limited company on Companies House, verify public liability and (if they employ staff) employers' liability insurance directly with the named insurer, and confirm any trade body or competent person scheme membership on the scheme's own website rather than trusting a logo on a van or quote.
Start with who you're actually contracting with
A builder might trade as a sole trader under their own name, as a partnership, or through a limited company. This matters because it affects who is legally responsible if something goes wrong and, in the case of a company, what financial protections (or lack of them) sit behind it.
Ask directly which of these applies and get the full legal name in writing. It should match the name on the quote, invoices and any insurance documents you're shown — a mismatch is worth querying before you go further.
Checking a limited company on Companies House
If the builder trades as a limited company, you can look up the company for free at Companies House. This tells you the registered address, how long the company has existed, whether accounts and confirmation statements have been filed on time, and whether any directors have other, dissolved companies in a similar trade.
A very recently formed company isn't automatically a problem — everyone starts somewhere — but it's a fact worth knowing before you hand over a deposit, and worth weighing alongside everything else you learn.
- Search the exact company name or number at find-and-update.company-information.service.gov.uk
- Check the registered address is a real, plausible business address
- Look at filing history for overdue accounts or confirmation statements
- Note the incorporation date — very new companies warrant a few more questions elsewhere
VAT registration
A VAT-registered builder should be able to give you their VAT number, which will appear on invoices. This isn't a guarantee of quality, but a consistent, verifiable VAT number is one more data point that lines up with a properly run business.
Verifying insurance directly with the insurer
Seeing an insurance certificate is a start, but certificates can be out of date or, rarely, altered. The safer approach is to ask for the insurer's name and policy number and then contact the insurer directly — not through a number the builder gives you — to confirm the policy is current and covers the type of work you're having done.
For public liability, this covers damage or injury caused to third parties or property during the work. If the builder employs staff, employers' liability insurance is a legal requirement under HSE rules and worth confirming separately.
Trade bodies and competent person schemes: check at source
Logos for trade associations or competent person schemes are easy to display on a website or van whether or not membership is current. Always verify membership on the scheme's own site using the builder's name or registration number, rather than trusting the logo.
- Gas work: check the engineer on the Gas Safe Register
- Electrical work: check registration with NICEIC or an equivalent competent person scheme
- General building work: check for TrustMark registration, which covers a range of trades under government-endorsed standards
References and site visits
Ask for two or three references from jobs of a similar size and type, ideally completed in the last year or two, and actually contact them. Where possible, ask to see a current or recently finished job in person rather than only photographs — it's far easier to judge tidiness, care and finish quality standing in a real space.
Online reviews: useful, but read with caution
Online reviews can be a helpful extra data point but are easy to manipulate in both directions — a small number of glowing or damning reviews can be misleading either way. Look for a reasonable volume of reviews over time, read a few of the more detailed ones rather than the star rating alone, and treat reviews as one input among several rather than a substitute for the checks above.
Practical checklist
- Full legal trading name obtained and matched across quote, invoice and insurance
- Sole trader vs limited company status confirmed
- Limited company checked on Companies House
- Company filing history reviewed for overdue accounts
- VAT number requested and noted, if applicable
- Public liability insurer name and policy number obtained
- Insurance confirmed directly with insurer, not just via certificate
- Employers' liability insurance checked if staff are employed
- Trade body or competent person scheme membership verified on the scheme's own site
- At least two references contacted directly
- A current or recent job viewed in person where possible
- Online reviews read for detail, not just star rating
Good and bad examples
What good looks like
A homeowner is given an insurer's name and policy number, calls the insurer directly to confirm cover is current, checks the builder's company on Companies House, and finds the NICEIC registration number checks out on the scheme's own website.
What to push back on
A homeowner accepts a photograph of an insurance certificate and a logo on the side of the van as sufficient proof, without contacting either the insurer or the scheme directly.
Commonly missed items
- Checking a certificate exists but never confirming it directly with the insurer
- Trusting a trade body logo without checking the scheme's own register
- Only checking Companies House for the company name, not the filing history
- Contacting references but not asking about programme, communication and how issues were handled
- Reading only the star rating on reviews and not the detail underneath
Warning signs
- Reluctance to provide an insurer's name and policy number
- Insurance certificate that appears altered, expired, or in a different company name
- Trade body logo that cannot be matched to a real entry on the scheme's register
- References that are unreachable or clearly rehearsed
- A run of very recent, very similar five-star reviews with little detail
Questions to ask
- What is your full legal trading name and structure?
- Can I have your insurer's name and policy number to confirm directly?
- Which competent person scheme, if any, are you registered with, and what's your registration number?
- Can I speak to two recent customers with similar jobs?
- Can I see a current or recently finished job in person?
When to seek professional advice
- If a company's Companies House record shows a pattern of dissolved companies in the same trade
- If an insurer cannot confirm a policy the builder has claimed to hold
- If a competent person scheme has no record of a registration number given to you
- If you're unsure how to interpret a Companies House filing history — Companies House support pages explain the terms used
Official sources
Frequently asked questions
- Is a sole trader automatically riskier than a limited company?
- Not automatically. Both structures include good and poor builders. The structure affects who is legally responsible and what protections apply, which is why it's worth knowing rather than assuming.
- How do I actually verify insurance rather than just seeing a certificate?
- Ask the builder for the insurer's name and policy number, then contact the insurer yourself using a number you find independently, not one supplied by the builder, and ask them to confirm cover is current.
- Does a TrustMark or NICEIC logo on a website prove current membership?
- No. Logos can be left up after membership lapses. Check the scheme's own register using the builder's name or registration number.
- How many references should I contact?
- Two or three, ideally for jobs similar in size and type to yours, completed reasonably recently.
- Should a lack of online reviews put me off a builder?
- Not necessarily — some good, busy builders rely on word of mouth rather than review platforms. Weigh it alongside references and direct checks rather than as a standalone red flag.
Builder Proof UK publishes general educational information for homeowners. It is not legal, structural, surveying, planning, electrical, gas, insurance or financial advice, and it does not replace advice from a suitably qualified professional for your specific project.