Contractor Checking Checklist: What to Check Before You Hire
Every check worth making on a building contractor, in the order that makes sense, from first contact to the moment you pay a deposit.
One list, in order
Checking a contractor is easier than it sounds. It is mostly a matter of doing a handful of things in the right order.
Each individual check on a builder is simple: read a certificate, look up a company, make a phone call. What makes it feel hard is knowing which checks matter, when to make them and what to do with the answers.
This checklist puts everything in sequence, from the moment you first contact a contractor to the point where you pay a deposit. Each stage links to a fuller guide if you want more detail.
No checklist removes risk entirely. What it does is make the likely problems visible early, while you are still free to walk away. For the wider picture, see our guide to choosing and checking a building contractor.
Stage one
Before the site visit
A few minutes of checking before anyone comes to your home.
Get the full business details
The legal name of the business, any trading name, a postal address, a phone number and an email address. If the business is a limited company, ask for the company name exactly as registered.
Look the business up
Limited companies are listed on Companies House, which is free to search on GOV.UK. Sole traders are not registered there, which is normal. Check the company name, its status and that the registered details match what you have been told.
Read reviews in more than one place
Look at reviews on more than one platform if you can, and read the detail rather than the score. Consistent comments about the same strengths or problems tell you most.
Check any memberships they claim
If a contractor says they belong to a trade body or scheme, check it on that organisation's own site rather than relying on a logo. Trade accreditation schemes explained covers the main ones.
Check a VAT number if they charge VAT
If the contractor is VAT registered, their VAT number should appear on the quotation. GOV.UK has a free service to check a UK VAT number is valid.
Stage two
At the site visit
The visit is where you gather most of the information you will check later.
Ask your prepared questions
About the job, the people, the paperwork, the price and the timing. The guide to questions to ask at a site visit sets them out.
Ask for the insurance certificate
Ask for a copy of the public liability insurance certificate, or for it to be sent with the quotation.
Ask for examples of previous work
Photos of similar jobs, and whether one or two past customers would be willing to talk to you.
Ask about permissions and approvals
Whether planning permission, Building Regulations approval or a party wall notice might be needed, and who would deal with each.
Notice how they communicate
Did they arrive when agreed? Did they explain clearly? Did they tell you when to expect the quotation? This is a preview of the job itself.
Stage three
Checking what they gave you
After the visit, check the documents and details you collected. Most of this can be done from home in an evening.
The insurance certificate
Check that the business name matches, the policy is in date and it includes public liability cover. If they employ staff, most employers are legally required to hold employer's liability insurance too. See checking a builder's insurance.
References
Speak to at least one past customer who had similar work done. Taking up references gives you the questions to ask.
Previous work
Look at photos of similar jobs and ask about them, or look at a finished job from the street. Checking previous work covers how.
Registrations for regulated work
Anyone doing work on gas appliances must by law be on the Gas Safe Register. If a contractor says they will self-certify work under Building Regulations, check their registration with the competent person scheme they name.
Waste carrier registration
If the contractor is taking your waste away, you can check they are a registered waste carrier on the public register for your part of the UK.
A contactable address
A business should be able to give you a postal address where it can be contacted in writing. Our answer on whether a builder should have a business address explains why it matters.
Stage four
Checking the quotation
A written quotation is the clearest record of what you are agreeing to. Read it slowly, and check it against your notes from the visit.
It should clearly state
- The name and contact details of the business doing the work
- What work will be done, in enough detail to check later
- The main materials to be used
- The price, and whether VAT is included
- The deposit and when the balance is due
- The expected start date and duration
- The workmanship warranty and its terms
- How long the quotation is valid
Ask about it if it's missing
- Scaffolding, skips and waste removal
- Anything priced as an allowance that could change
- How extra work would be agreed and priced
- Who deals with building control, where needed
- Making good after the work, such as plaster or paint
- Clearing up at the end
- Who you contact during the job
Stage five
Before you pay a deposit
Have the terms in writing. Whether it is a formal contract or the terms attached to a quotation, you should know before paying anything what you are agreeing to: the work, the price, the payment stages and what happens if plans change. Our answer on what paperwork to get before work starts lists the essentials.
Check the deposit is proportionate. A deposit to secure a start date or order materials is normal. A request for most of the price before any work begins is worth questioning.
Pay in a way that leaves a record. Bank transfer or debit card to the business named on the quotation gives you a clear record of who you paid and when. Paying cash leaves very little, which makes any later disagreement about what was paid harder to settle.
Know your cancellation rights. If you agree a contract with a trader somewhere other than their business premises, such as in your own home, you usually have a legal right to cancel within 14 days under consumer contract rules. If you ask for work to start within that period, you may have to pay for work already done. Citizens Advice explains how this works in practice.
This is general information, not legal advice.
Larger projects
Extra checks for bigger jobs
For a repair or a single rooflight, the five stages above are usually enough. For an extension, a loft conversion or anything lasting several weeks, a few more checks are worth the time.
Match the contractor to the scale. Ask about the largest similar job they have run, how many people they will have on site and who will manage it day to day. A contractor who excels at small jobs may not be set up for a long build, and the reverse can also be true.
Look at the payment stages. On a longer job, payments are often split into stages tied to progress. Check that each stage is linked to a clear point in the work, so you are paying for what has been done rather than ahead of it.
Consider a written contract. For larger work, a written contract gives both sides more certainty than a quotation alone. Standard-form building contracts written for homeowners are published by bodies such as the Joint Contracts Tribunal (JCT), and some contractors use their own terms. Either way, read it before you sign, and take advice if anything is unclear.
Know where the approvals stand. If the project needs planning permission, Building Regulations approval or party wall agreements, check what is in place before work starts and who is responsible for each. Our guide to what a main contractor is responsible for explains what usually sits with the contractor and what stays with you.
Plan for changes. Larger projects often uncover things nobody could see at the start. Agree how changes will be priced and approved, ideally in writing before the extra work is done.
Keep the quotation, the insurance certificate, any messages that confirm what was agreed, and receipts for each payment together, paper or digital. It takes a few minutes and makes any later conversation about the work much easier.
Weighing it up
What to do with the answers
The point of checking is to make a decision, not to collect a perfect score.
One gap is not a verdict
A contractor without a polished portfolio, or with one mediocre review among many good ones, may still be a strong choice. Ask about gaps and weigh the answer.
Patterns matter
Several small concerns pointing the same way, such as vague answers, missing documents and pressure to decide, deserve more weight than any one of them alone. Red flags when hiring a builder sets out the common ones.
Openness is a good sign
Contractors who hand over documents readily, answer directly and put things in writing make everything else easier to check. That in itself tells you something.
When we coordinate the work
Five checks made before you're introduced
When Mortaro coordinates a project, every contractor in our network was checked for public liability insurance, reviews and references, the warranties they provide, trade experience and prior work history, and their ability to meet our standards before being introduced to any customer. We tell you exactly what those checks are, rather than describing contractors as fully vetted.
Checks reduce the risk of ending up with the wrong contractor; they don't remove it. Your contractor is named in your written quotation, so you can make any checks of your own before committing. Our contractor network explains the checks and what happens when a contractor falls short.
Straight answers
Questions about checking contractors
How long does it take to check a contractor properly?
Most of the checks on this list take a few minutes each. Speaking to a reference and reading the quotation carefully take longer. It is a small investment compared with the cost of the work.
Is it acceptable to ask a builder for all of this?
Yes. Asking for insurance, references and a written quotation is normal, and established contractors expect it. How readily they respond is useful information in itself.
What if a builder is a sole trader with no Companies House record?
That is normal. Sole traders are not registered at Companies House. Focus on the other checks: insurance, references, previous work, a contactable address and a clear written quotation.
How do I know if a builder is legitimate?
No single check proves it, but a business that gives full contact details, provides a current insurance certificate, has checkable references and puts its price in writing is showing the right signs. Our answer on how to know a builder is legitimate goes further.
Do I need to check a contractor recommended by a friend?
It is still worth running the basics. A recommendation tells you the contractor did good work for someone you trust, but it doesn't tell you whether their insurance is current or whether they are the right fit for your particular job. A quick look at their insurance certificate and a clear written quotation cover most of what matters.
Start here
Tell us about the work you have in mind
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