Using Subcontractors in Your UK Trade Business — CIS, Contracts and IR35 in 2026

Most trade businesses reach a point where they can't take on every job with their own hands. A busy roofing firm needs a groundwork crew for drainage. A plumber wins a bathroom contract but wants to sub out the tiling. An electrical contractor lands a housing development and needs three extra sparkies for six weeks. Subcontracting is how UK trade businesses flex capacity without carrying the fixed cost of a full payroll.

Done right, it gives you speed, specialist skills and the ability to quote for bigger jobs. Done wrong, it hands HMRC a reason to investigate your business, leaves you exposed if a subbie injures someone on site, and can result in a tax bill you weren't expecting. This guide covers everything you need to get it right in 2026.

Why trade businesses use subcontractors

The most common reason is peak demand. You've got more work than your own team can handle, and you don't want to turn it away or delay it by weeks. Taking on a permanent employee to cover a spike costs you in recruitment, PAYE, pension contributions and employer's NI — even after the spike ends. A reliable subbie costs you nothing when there's no work on.

Specialist skills are the second reason. A plumbing business might be excellent at heating systems but slower on tiling. Rather than lose margin doing work that isn't your strength, you sub it to a tiler who'll do it faster and better. The client gets a better result, your margin holds up, and you look capable of managing a full bathroom package. The same logic applies to a builder who sub-contracts electrical first fix, or a roofing contractor who uses a specialist lead worker for complex flashing.

Geographic reach is another driver. If you're based in Birmingham but win a job in Coventry, it's easier to use a local groundwork crew who know the area and don't rack up travel time on your quotes. You stay in charge of the project, handle the client relationship and take your management margin — without stretching your own team.

CIS: what contractors must know

If you pay subcontractors for construction work, you're likely operating as a contractor under the Construction Industry Scheme (CIS). This applies to most trade businesses paying subbies — the £3 million annual spend threshold that exempts some businesses from registering as contractors applies only to businesses whose core activity is not construction (such as a supermarket chain that happens to commission building work). If you're a trade business paying subcontractors to carry out construction operations, you must register as a contractor with HMRC regardless of spend.

Registering as a CIS contractor

Register through HMRC's CIS online service. You'll need your UTR (Unique Taxpayer Reference) and employer PAYE reference. Once registered, you're responsible for verifying every subcontractor before you pay them, making the correct deductions, and filing monthly returns.

Verifying subcontractors

Before you pay any subcontractor for the first time, you must verify their registration status with HMRC via the CIS online service or by calling the CIS Helpline. The verification tells you which deduction rate to apply:

• 0% — Gross payment status: The subbie has applied and been approved to receive payments in full. HMRC grants this only to subcontractors who meet turnover, compliance and business tests. You pay the full amount and they handle their own tax.
• 20% — Standard deduction rate: The subbie is registered under CIS but does not hold gross payment status. You deduct 20% of the labour element (not materials) from each payment and pass it to HMRC.
• 30% — Unverified/higher rate: The subbie cannot be verified — either they're not registered for CIS or their details don't match HMRC records. You must deduct 30% and pay it to HMRC. This also applies if the subbie gives you incorrect details.

Always keep a record of the verification reference number HMRC gives you. If you fail to verify and apply the wrong rate, the liability for any shortfall falls on you as the contractor.

What deductions apply to

CIS deductions apply only to the labour portion of the payment — not to the cost of materials the subcontractor has purchased for the job. If a plumber invoices you £2,000 and £600 of that is for materials (pipe, fittings, etc.), you apply the deduction only to the £1,400 labour element. The subbie must be able to evidence their material costs if HMRC asks.

Monthly CIS returns (CIS300)

Every month you pay subcontractors under CIS, you must file a CIS300 return with HMRC. This shows each subcontractor you paid, the gross amount, the materials amount and the deduction made. The deadline is the 19th of the following month. If you pay by post, allow time for it to arrive — the deadline is earlier.

If you made no payments in a given month, you still need to notify HMRC of a nil return, or you'll receive a penalty as if you missed the filing entirely.

Penalties for late CIS returns

• Up to 2 months late: £100 per return
• 2–6 months late: £200 per return
• 6–12 months late: £300 or 5% of deductions due (whichever is higher)
• Over 12 months late: £3,000 or 100% of deductions due (whichever is higher) in the most serious cases

These stack per return, so if you've been missing returns for several months, the penalties add up fast. Get into a routine — file on the same day each month, even if it's a nil return.

Employment status: getting it right matters

One of the biggest risks in using subcontractors is HMRC deciding that a person you've been treating as self-employed is actually an employee. If they make that determination, you become liable for the employer's NI, income tax and employee NI that should have been deducted — plus interest and penalties going back years. It is your problem, not the subcontractor's.

HMRC uses a set of tests to determine employment status. No single test is decisive — it's a holistic picture:

The key employment status tests

• Control: Do you control how the work is done, what hours the person works, and where they work? If you dictate working hours, direct day-to-day tasks and tell them exactly how to complete the job, that looks like employment. A genuine subbie is told what to deliver, not how to deliver it.
• Financial risk: Does the subcontractor bear genuine financial risk? A self-employed person quotes a price and absorbs the cost if the job takes longer or materials cost more. Someone who is paid a day rate regardless of output, and whose tools and van are provided by you, looks more like an employee.
• Right of substitution: Can the subbie send someone else to do the work if they're unavailable? Genuine self-employment usually includes the right to substitute. If the contract says only that named individual can do the work, that's a pointer toward employment.
• Integration: Is the person integrated into your business? If they wear your branded uniform, use your email address, are listed on your website as staff, or have been working for you exclusively for two years, HMRC will take a close look.
• Mutuality of obligation: Are you obliged to offer work and is the subbie obliged to accept it? If the answer to both is yes, that's a strong pointer toward employment. True self-employment involves no obligation on either side.

Use HMRC's Check Employment Status for Tax (CEST) tool before engaging a subcontractor you're unsure about. It's not legally binding, but it documents your thinking and gives you a defence if challenged later. Keep the result on file.

IR35 and trade businesses

IR35 (off-payroll working rules) is most commonly associated with IT contractors and consultants, but it can apply to trade businesses operating through limited companies. If a subcontractor provides their services through a personal service company (PSC) — their own limited company — and the work would look like employment if the company didn't exist in the middle, IR35 may apply.

For most small trade businesses using sole trader subbies on short-term jobs, IR35 is not the primary concern. But if you regularly use a subcontractor who works through their own Ltd company, works exclusively for you over extended periods, and has little financial independence from your business, you should assess the arrangement carefully. The rules for determining liability shifted in 2021 — medium and large businesses (not small businesses) are responsible for determining the IR35 status of contractors they engage through intermediaries. However, if you're approaching medium-business thresholds, take advice.

Written subcontractor agreements

Never start a subcontractor on site without a written agreement. A handshake is not enough when there's a dispute over defects, a delay to payment, or an injury on site. A proper subcontractor agreement does not need to be a lengthy legal document — it should be clear, practical and signed before work starts.

What to include in your subcontractor agreement

• Scope of work: Exactly what the subcontractor is doing. Reference drawings or specifications if relevant. Ambiguity here causes disputes.
• Rate or fixed price: Whether it's a day rate or fixed-price contract, state the amount clearly. If fixed price, specify what is and is not included.
• Payment terms: When invoices should be submitted, how long you have to pay (30 days is standard), and how disputes over invoices are handled. The Late Payment of Commercial Debts Act applies — if you're late paying a subbie, they can charge statutory interest.
• Start and end dates: Even approximate dates. This helps manage your project schedule and supports the self-employment argument (a defined engagement rather than open-ended employment).
• CIS deductions clause: State clearly that deductions will be made in accordance with the CIS at the applicable rate, and that a deduction statement will be provided monthly. This avoids arguments at invoice time.
• Insurance requirements: Specify that the subcontractor must hold public liability insurance of at least £2 million (£5 million for larger sites or more complex work), and provide a copy of the certificate before work starts. Include any professional indemnity requirement if relevant.
• Liability: Who is responsible for defective workmanship, and for how long. State whether the subcontractor is liable for remedial work if defects arise from their scope within a defined period.
• Defects liability period: Typically 12 months from practical completion of their work. If you face a claim from your client, you want to be able to recover from the subbie whose work caused it.
• Health and safety obligations: The subcontractor must comply with site rules, risk assessments and method statements, and operate under your site induction. Make it explicit that they are responsible for their own and their workers' safety.
• Confidentiality: If you're working on a high-profile project or the client has requested it, include a simple confidentiality clause.
• Self-employment declaration: A clause stating that the subcontractor is self-employed, is responsible for their own tax affairs, and is not an employee of your business. This supports your status position — though note it is not by itself determinative.

Insurance: never cut corners

If an uninsured subcontractor causes damage to a client's property or injures a third party on your site, the claim will come to you. Your own public liability policy may not cover work carried out by a subcontractor — check the policy wording carefully. Many trade PL policies do cover subbies up to a point, but only if you have taken reasonable steps to ensure the subbie holds their own insurance.

Insurance checks before every engagement

• Get a copy of the subcontractor's public liability certificate before they step on site. Not a verbal confirmation — an actual PDF or printed copy.
• Check the limit. £2 million is the minimum for most domestic and light commercial work. For larger sites, commercial fit-outs or work involving members of the public, require £5 million. Some principal contractors will specify £10 million.
• Check the expiry date. An expired certificate is worthless. If it runs out mid-job, get the renewal before work continues.
• Check that the work they're doing is covered by the policy. A decorator's PL policy may not cover them if they're also doing structural work — the activity must fall within the policy schedule.
• If the subbie carries out design or specification work (not just physical installation), check whether professional indemnity insurance is needed.

Keep copies of all certificates in a simple spreadsheet or folder with renewal dates noted. A subbie turning up on site without valid insurance is a problem you can prevent with a five-minute admin check.

Day rates vs fixed price

How you structure the deal with a subbie affects your cost predictability, your relationship and — to a limited degree — your employment status position.

Day rates

Day rates are simple and flexible. You pay for time, and if the job runs over, you pay more. This works well for reactive work, where scope is uncertain, or on large projects where there are a lot of unknowns. The risk sits with you — if the job drags, your cost rises. Day rates can also be a minor flag for employment status (since employees are commonly paid by time), so combine them with clear project scope and defined end points.

Typical day rates for UK trade subcontractors in 2026 (exclusive of materials and VAT):

• General builder / labourer: £150–£250 per day
• Electrician: £180–£280 per day
• Plumber: £160–£260 per day
• Gas engineer: £170–£270 per day
• Plasterer: £150–£250 per day
• Tiler: £140–£220 per day
• Groundworker: £150–£220 per day
• Roofer: £160–£260 per day
• Carpenter / joiner: £160–£260 per day
• Painter / decorator: £130–£210 per day

These vary significantly by region — London and the South East will be at or above the top of these ranges, while rural areas in the North or Wales may be at the lower end.

Fixed price

Fixed price (or lump sum) gives you cost certainty and is a stronger indicator of genuine self-employment — the subbie takes on the financial risk of the work taking longer than expected. It works well when scope is clearly defined. For a tiler doing a bathroom, a fixed price per square metre is common. For a groundworker doing a specific drainage run to a drawing, a fixed price for the whole job makes sense.

The risk with fixed price is scope creep. If additional work is discovered — say, the substrate under the tiles needs repair — make sure your agreement includes a clear process for agreeing variations before the subbie proceeds. Otherwise you end up with a dispute at the end about whether extras are included in the price.

Managing quality on site

The client holds you responsible for the finished job — not the subcontractor. Even if a subbie does poor work, your client relationship and your reputation are on the line. Quality management is not optional.

Before the job starts

• Provide a clear scope with drawings, specifications or reference images where relevant. Don't assume they know what standard you expect — show them.
• Walk the site with the subbie before they start, especially if there are existing conditions that affect their work (e.g. substrate condition, existing services, access restrictions).
• Agree the standard expected — for finishes especially, show a sample or reference finish if possible.

During the job

• Take photos at key stages — before and after covering up work, mid-point on longer jobs. These are invaluable if a dispute arises later about what was done.
• Visit site regularly if the job is more than a day or two. You don't need to micromanage, but a check-in every couple of days catches problems early.
• If something looks wrong, say so straight away. Problems caught at first-fix are easy to correct; problems discovered at handover are expensive.

Snagging and sign-off

Before you release final payment to a subcontractor, carry out a proper snagging walkthrough. Create a written snag list, share it with the subbie, and agree a timescale to resolve items. Do not pay in full until the snag list is signed off — once you've paid, your leverage is gone. Make the snag process part of your standard agreement so subbies know it's coming and build it into their schedule.

Defects that appear after the subbie has left site and been paid are harder to deal with. Your subcontractor agreement's defects liability clause gives you a legal route, but in practice you want to catch problems before final payment wherever possible.

Building a reliable pool of subcontractors

The biggest operational headache in using subbies is reliability. The best trade businesses maintain a small, trusted pool of three to five subcontractors per trade they use regularly. These subbies know your standards, know how you work and will prioritise you when they're busy — because you've earned that by being a good client.

How to be a client subbies want to work for

• Pay on time, every time. Thirty days is the standard. If you can pay faster — say within 14 days of invoice — you will be at the top of their list when work is tight. Cash flow is as important to subbies as it is to you. A reputation for slow payment means you get cancelled when a better client calls.
• Give them good jobs. If you only call a subbie for the awkward, badly-specified, last-minute jobs that nobody else wants, they'll figure that out quickly. Share the good work too.
• Be organised on site. Have materials ready, access arranged and the scope clear before the subbie arrives. Showing up to find nothing is ready wastes their time and yours, and they'll factor that into whether they want to work with you again.
• Communicate clearly. Changes in programme, access issues, material delays — tell them as soon as you know. Subbies who feel respected and informed will be more flexible when things go wrong.
• Give feedback. If someone does a good job, say so. If there are areas to improve, say that too — constructively. Subbies who never hear anything assume everything is fine, and problems repeat.

The best subcontractors are usually booked four to six weeks out. If you want them on your jobs, build the relationship before you need them urgently. The time to develop your subbie pool is when you're not under pressure.

Keeping records

HMRC can open a CIS compliance check at any time. You need to be able to demonstrate that you verified each subcontractor, applied the correct deduction rate, filed returns on time and paid the right amount. Keep records of:

• Verification reference numbers for each subcontractor
• Copies of all subcontractor invoices, showing gross amount, materials and labour split
• Copies of all CIS300 returns filed
• Payment records showing gross paid and deduction made
• Deduction statements given to each subcontractor each month
• Insurance certificates (current copies)
• Signed subcontractor agreements

HMRC can go back six years in a standard review and further if they suspect fraud. Keep records for at least six years from the end of the relevant tax year.

Common mistakes to avoid

• Failing to verify before paying: If you skip verification and apply the wrong rate, you're liable for the difference. Always verify, always record the reference number.
• Letting insurance lapse: Don't assume a certificate you got six months ago is still current. Diary the renewal dates and chase before they expire.
• Treating subbies like employees: Setting their hours, providing all their tools, giving them company email addresses — all of these weaken your self-employment argument and increase HMRC investigation risk.
• No written agreement: A verbal agreement is unenforceable in practice. When a dispute arises — and eventually it will — you need something to point to.
• Paying before snagging: Once you've paid in full, your leverage disappears. Always snag before final payment.
• Missing nil returns: Even if you haven't paid any subbies in a given month, you must submit a nil CIS return. Many contractors get caught by this and accumulate penalties unnecessarily.

Summary

Subcontracting is a legitimate and powerful tool for UK trade businesses — it lets you take on more work, access specialist skills and manage capacity without the permanent cost of employment. But it carries real obligations: CIS registration and monthly returns, employment status diligence, written agreements, insurance verification and quality management. Get these foundations right and subcontracting becomes a growth lever. Ignore them and you're building on sand, one HMRC letter away from a serious problem.

Build your pool of reliable subbies now, pay them on time, treat them well and they'll be there when you need them most.