How to check if a builder is legitimate in the UK

Hiring a builder for a home renovation involves handing over significant sums of money to someone you may have met once or twice. Unlike many other professional services, there is no mandatory licensing scheme for builders in England and Wales. Anyone can call themselves a builder and start trading tomorrow. This makes due diligence (checking that your builder is who they claim to be) your responsibility.

The good news is that the checks are straightforward, mostly free, and can be completed in an afternoon. Here is exactly what to look for and where to find it. The checks lower the risk of hiring badly; how you pay limits the cost if something still goes wrong, so once you have chosen, ask your builder to use milestone-based payment protection as well.

Check Companies House for their registered business

Start at Companies House (find-and-update.company-information.service.gov.uk). Search for the builder's company name or their personal name if they are a sole trader operating through a limited company.

You are looking for several things. First, that the company exists and is listed as "Active." A company that is dissolved, in liquidation, or has a proposal to strike off is an immediate disqualification. Second, check the incorporation date. A company registered last month carries more risk than one that has been trading for five years. Third, look at the filing history: are accounts and confirmation statements filed on time, or are there persistent late filings? Late filings suggest disorganisation at best and financial distress at worst.

Check the registered office address. If it is a residential address in a different part of the country from where the builder claims to operate, ask questions. Also note the names of the directors. If the builder you are speaking to is not listed as a director or person of significant control, find out who is and why.

If the builder is a sole trader (not a limited company), they will not appear on Companies House. This is not inherently a problem (many legitimate builders operate as sole traders), but it does mean you have fewer public records to verify.

Verify their insurance cover

Any builder working on your property should carry public liability insurance as a minimum. This covers damage to your property and injury to third parties caused by the builder's work. For most residential projects, a policy of at least £2 million is appropriate; for larger projects involving structural work, £5 million or more is advisable.

Ask the builder for a copy of their insurance certificate, not just verbal confirmation. The certificate should show the policy number, the insured party's name (which should match the builder's company or trading name), the coverage amount, and the expiry date. If the policy has expired, it is worthless.

Some builders also carry employer's liability insurance (legally required if they have employees) and professional indemnity insurance (useful if they are providing design services). Check which policies they hold and whether the coverage is appropriate for the scale of your project.

Look for trade body membership

Trade body membership is not compulsory for builders in England and Wales, but it is one of the strongest voluntary signals of professionalism. The main trade bodies for residential builders include the Federation of Master Builders (FMB), TrustMark, the British Association of Landscape Industries (BALI), and the National Federation of Builders (NFB).

Each of these organisations has admission criteria that typically include proof of insurance, financial vetting, and in some cases site inspections or competency assessments. Membership can be verified directly on the trade body's website. Do not rely on the builder's claim alone.

TrustMark membership is particularly worth checking because it is a government-endorsed quality scheme, and many TrustMark members offer deposit protection and insurance-backed guarantees. If your builder is TrustMark registered, you have an additional layer of recourse if something goes wrong.

Some trades need a specific registration. Anyone working on gas appliances must be on the Gas Safe Register, and you can check an engineer's ID card number on the register itself. Electrical and window installers usually belong to a competent person scheme, which lets them certify their own work as meeting the Building Regulations. From late 2026 there is also the government-backed Approved Code for home improvement traders; we explain it in what the cowboy builder scheme means for homeowners.

Read independent reviews across multiple platforms

A builder's own website will only show positive testimonials. To get an honest picture, check independent review platforms: Checkatrade, MyBuilder, Houzz, Google Business Profile, and Bark.

Look for volume and consistency. A builder with 80 reviews averaging 4.5 stars across two platforms is a stronger signal than one with five reviews all scoring 5.0 on a single platform. Pay attention to negative reviews: not just the rating, but how the builder responded. A professional response to a complaint ("we acknowledge the issue and returned to fix it") tells you far more than a defensive or aggressive one.

Search for the builder's company name on Google alongside terms like "complaint," "dispute," or "county court." This can surface issues that do not appear on review platforms, including CCJs (county court judgments) that indicate unpaid debts or legal disputes.

To judge whether reviews are genuine, look at the pattern rather than the score. A burst of five-star reviews posted within a few days, short generic wording, and reviewers who have only ever left one review are all warning signs. Genuine reviews tend to mention the project, the area and the people involved. Since April 2025, posting or commissioning fake reviews has been banned under the Digital Markets, Competition and Consumers Act 2024.

Ask for references and visit a completed project

Online reviews are useful, but speaking directly to a previous client is more informative. Ask the builder for three references from projects completed in the past 12 months, and make sure the projects are comparable to yours in scope and value.

When you contact the references, ask specific questions. Did the project finish on budget? Were there unexpected costs or variations? How responsive was the builder when issues arose? Did they come back to resolve snagging items? Would you use them again?

If possible, ask to visit a completed project. Seeing the quality of the builder's work in person (the finish of the plastering, the alignment of the tiling, the neatness of the cabling) gives you information that no photograph or review can provide.

Check their VAT registration if the project is over £20,000

If your project costs more than £20,000 (including labour and materials), it is worth checking whether the builder is VAT registered. The current VAT registration threshold in the UK is £90,000 in turnover. A builder who has been trading for several years and is not VAT registered is either very small (which may be fine) or may not be declaring all of their income (which raises questions about their overall business practices).

You can verify VAT registration on the HMRC VAT registration checker. If the builder charges you VAT, their VAT number should appear on every invoice, and you can verify it is valid.

Know who checks the work, and who doesn't

No one inspects every job a builder does. Building control checks that notifiable work meets the Building Regulations: things like foundations, structure, drainage, fire safety and insulation on an extension or loft conversion. It can be your council's building control team or a registered building control approver, and your builder should tell you which one is involved before work starts.

Building control looks at compliance, not finish. It won't comment on uneven plastering or a badly fitted kitchen. At the end of notifiable work, ask for the completion certificate, and keep it with your property documents because you will need it when you sell. For everything else, the person checking the work is you, which is why it pays to approve each stage only when you're happy with it.

Warning signs to watch for while you check

The checks above tell you whether a builder exists on paper. How a builder behaves while you are doing them tells you the rest. These patterns show up before any money changes hands, which is the point at which they are cheapest to act on.

They resist putting anything in writing

A professional builder expects to work from a written contract. It protects them as much as it protects you: it defines the scope, prevents misunderstandings about what is included, and provides a framework for managing variations. "We don't usually bother with contracts" is a sign that they want flexibility to change the scope, the price or the timeline without accountability. A clear scope of work, a materials specification, a payment schedule structured as stage payments, start and completion dates, and a process for changes is enough. If the builder will not sign that, find one who will.

They ask for a large deposit with no breakdown

Aim for a deposit of no more than 10 to 15% (see how much deposit to pay). A request for 25 to 50% upfront with no breakdown of what the money is for is one of the strongest warning signs available, because it often means incoming money is funding the previous job. Ask for an itemised materials list and offer to pay the suppliers directly, or ask your builder to use milestone-based payment protection, so the money for each stage is held securely before work starts and released when you approve it.

They pressure you to decide quickly

"Another client wants this slot" and "I can only hold this price until Friday" are pressure tactics. Good builders are busy, but a professional will give you reasonable time to review a quote, check references and get the contract in order. Never pay a deposit under time pressure. If the builder will not wait 48 hours for you to verify their credentials and run the numbers through the Renopay stage planner, the urgency is serving their interests, not yours.

Their quote is far below everyone else's

If two builders quote £55,000 and £60,000 for your extension and a third comes in at £38,000, the third should concern you more than it excites you. Unusually low quotes often mean the builder has underestimated the scope, plans to use lower-quality materials or uninsured labour, or intends to recover the difference through variation claims once work is under way. Compare quotes on scope, materials specification, payment terms and track record, not the bottom line.

They cannot show you similar work

A builder trading for more than two years should be able to give you at least three recent references and photographs of completed projects like yours. Vague references with no names or contact details are a gap in your due diligence, not a substitute for it.

Use digital tools to assess risk before committing

The verification steps above give you a strong foundation, but they are manual and time-consuming. Digital tools can help streamline the process and identify risks you might miss.

The Renopay stage planner generates a fair stage payment schedule for your project (a sensible deposit with every later payment tied to completed work), so the money side is structured before anyone starts. Use it alongside your manual due diligence to build a complete picture before signing a contract or paying any money.

If you are satisfied that the builder is legitimate, the next step is to protect yourself through the payment structure. Even a verified, reputable builder can encounter financial difficulty or deliver work that does not meet expectations. Milestone-based escrow services such as Renopay are designed to keep your financial exposure at any point in line with the work completed, so that verification and payment protection work together as complementary layers of safety. The warning signs above cover the behaviour to watch for alongside the paperwork.

Frequently asked questions

Do builders need to be licensed in England and Wales?

No. There is no mandatory licensing scheme for builders in England and Wales, so anyone can call themselves a builder and start trading. That puts due diligence on you: check Companies House, see a current insurance certificate, verify any trade body membership such as FMB or TrustMark on the body’s own website, and read independent reviews.

How much public liability insurance should a builder have?

For most residential projects, public liability cover of at least £2 million is appropriate, and £5 million or more is advisable for larger projects involving structural work. Ask for the certificate rather than verbal confirmation, and check that the insured name matches the builder’s company or trading name and that the policy has not expired.

How do I check if a builder is registered?

There is no single register of builders in the UK. Check Companies House if they trade as a limited company, verify any trade body or TrustMark membership on that body’s own website, and for gas work check the engineer on the Gas Safe Register, which is a legal requirement. From late 2026 you can also see whether a trader has signed up to the government-backed Approved Code.

Who checks a builder’s work in the UK?

Building control checks that notifiable work, such as extensions, structural alterations and new drainage, meets the Building Regulations. That is either your council’s building control team or a registered building control approver. They check compliance, not the quality of the finish, so ask for the completion certificate at the end and inspect the workmanship yourself before you pay for each stage.

Is a large deposit a red flag when hiring a builder?

It can be. Aim for a deposit of no more than 10 to 15% of the contract value. A request for 25 to 50% upfront without a detailed breakdown of what the money is for is a serious warning sign. If a larger sum is needed for materials, ask for an itemised materials list and offer to pay the suppliers directly.

Should I accept the cheapest quote from a builder?

Not on price alone. An unusually low quote can mean the builder has underestimated the scope, plans to use lower-quality materials or unqualified labour, or intends to recover the difference through variation claims once work is underway. Compare quotes on scope, materials specification, payment terms and the builder’s track record, not just the bottom-line number.

What should I ask a builder’s references?

Contact them directly and ask specific questions. Did the project finish on time? Were there any unexpected costs? How did the builder handle problems? Would they hire the builder again? A builder who has been trading for more than two years should be able to give you at least three recent references and photos of completed projects similar to yours.

How can I check a builder who is a sole trader?

Lean on the checks that do not depend on Companies House, because a sole trader will not appear there: a current public liability insurance certificate, trade body membership verified on the body’s own website, independent reviews and references from comparable recent projects. Trading as a sole trader is not a problem in itself, as many legitimate builders work this way.