What Makes Construction Subcontractors Different for Tax Purposes?

If you work in construction as a subcontractor, your tax situation is not the same as a standard freelancer or limited company director. The Construction Industry Scheme (CIS) changes how payments are handled, how much tax you pay upfront, and how you reclaim overpaid deductions at year end.

Get it wrong, and you could be sitting on thousands of pounds of overpaid tax for months. Get it right, and you keep your cash flow healthy and your HMRC compliance clean.

That is why finding the right accountant for construction subcontractors matters. You need someone who knows the CIS rules inside out, understands VAT flat rate for construction, and can spot the traps that trip up most tradespeople.

How the Construction Industry Scheme Actually Works

CIS is HMRC's system for tracking payments from contractors (the main builders or developers you work for) to subcontractors (you). When a contractor pays you, they must deduct tax from your invoice at source and pay it directly to HMRC.

The deduction rates are:

  • 20% for registered subcontractors (you have given the contractor your Unique Taxpayer Reference and they have verified you with HMRC)
  • 30% for unregistered subcontractors (you have not provided your UTR or the contractor has not verified you)

If you are registered as a gross payment subcontractor, the contractor pays you in full with no deductions. That is the goal for most subcontractors, but it requires a clean compliance record and a turnover test.

At the end of the tax year, you file your self assessment return (SA100 with SA103 self-employment pages). HMRC compares the CIS tax deducted against your actual tax bill. If too much was deducted, you get a refund. If not enough, you pay the difference.

This is where a specialist accountant for construction subcontractors earns their keep. They ensure you claim every penny of overpaid CIS tax back, and that you do not miss the deadline for doing so.

Why You Need an Accountant Who Knows Construction, Not Just Tax

A general accountant can file your self assessment. But a construction specialist understands the specific problems you face every day.

CIS Deduction Errors Are Common

Contractors get the CIS rate wrong all the time. They might deduct 30% when they should have deducted 20%. They might forget to issue you a CIS statement (CIS300) showing what was deducted. Without that statement, you cannot claim the credit on your tax return. An accountant who knows CIS will chase those statements and check every deduction against your records.

VAT Flat Rate Scheme for Construction

Most construction subcontractors use the VAT Flat Rate Scheme. The standard flat rate for building trades is 9.5% (or 14.5% for labour-only contractors). But the Limited Cost Trader rules changed everything. If you spend less than 2% of your turnover on relevant goods (not including capital expenditure or food), you must use the 16.5% flat rate. Many subcontractors fell into this trap without realising. A construction accountant will calculate whether the flat rate scheme still works for you or whether standard VAT accounting is better.

IR35 and the Construction Sector

If you work through your own limited company for a single contractor or agency, IR35 may apply. Construction is one of the most scrutinised sectors for IR35. If HMRC decides you are a disguised employee, the contractor (or agency) is responsible for deducting PAYE and NI from your payments. That can wipe out your take-home pay. An accountant who understands IR35 in construction will help you structure your engagement to stay outside IR35 where genuinely possible, and advise on what to do if HMRC challenges you.

Employment Status and CIS: The Confusion

CIS treats you as self-employed for tax purposes. But HMRC can still argue you are an employee for employment law or IR35 purposes. The two regimes do not align. A construction accountant will help you understand where you stand and what records you need to keep to defend your status if HMRC investigates.

What a Good Construction Accountant Does for You

Here is the practical difference a specialist accountant for construction subcontractors makes to your business.

They Set Up Your Business Structure Correctly

Most construction subcontractors operate as sole traders or limited companies. Sole trader is simpler and cheaper. Limited company offers more tax planning flexibility and protects your personal assets from business liabilities. But the right choice depends on your turnover, the type of work you do, and whether you work through agencies. An accountant will run the numbers for your specific situation. If you are considering incorporating, read our guide on incorporation for contractors.

They Handle Your CIS Returns and Monthly Deductions

Every month, you need to reconcile the CIS deductions shown on your contractor statements against what HMRC records. If there is a mismatch, you need to sort it out quickly. An accountant can do this for you, or give you a simple system to follow so nothing slips through the cracks.

They Maximise Your Allowable Expenses

Construction subcontractors can claim a wide range of expenses: tools, equipment, PPE, van costs, fuel, training, professional fees, insurance, and more. But the rules around capital allowances, mileage, and mixed-use assets are specific. A construction accountant will ensure you claim everything you are entitled to without triggering an HMRC enquiry by claiming things that look unreasonable.

They File Your Self Assessment and CIS Refund Claim

This is the big one. If you have had CIS tax deducted at 20% or 30% and your actual tax bill is lower, you are due a refund. But you must file your self assessment return on time to claim it. The deadline is 31 January after the end of the tax year. Miss it, and you lose the refund for that year. A construction accountant will file your return early and get your refund processed as quickly as HMRC allows.

They Keep You MTD Ready

Making Tax Digital for Income Tax (MTD for ITSA) becomes mandatory for self-employed people and landlords with qualifying income over £50,000 from April 2026. That drops to £30,000 from April 2027 and £20,000 from April 2028. If you are a sole trader subcontractor turning over more than £50,000, you need to be using MTD-compatible software now. An accountant will set you up with the right software (Xero, FreeAgent, QuickBooks, or GoSimpleTax depending on your needs) and make sure your records are digital-ready.

How to Choose the Right Accountant for Construction Subcontractors

Not all accountants who say they work with contractors actually understand CIS. Here is what to look for.

  • ICAEW or ACCA qualified. That means they are regulated and have professional indemnity insurance. Our team at Holloway Davies are ICAEW qualified accountants with specific experience in the construction sector.
  • Experience with CIS specifically. Ask them how many construction subcontractors they work with. The answer should be more than a handful.
  • They use cloud accounting software. If they still want paper receipts and spreadsheets, walk away. You need real-time visibility of your tax position.
  • They offer fixed fees. Construction subcontractors do not need surprise bills. A good accountant will quote a fixed monthly or annual fee for your work.
  • They know your local area. If you work in Manchester, Birmingham, Bristol, or London, an accountant who understands the local construction market and rates is valuable.

What Does a Construction Accountant Cost?

Fees vary depending on whether you are a sole trader or limited company, how many contractors you work for, and whether you need monthly bookkeeping or just annual accounts.

Typical ranges for a construction subcontractor accountant in 2025/26:

  • Sole trader, annual return only: £300 to £600 per year
  • Sole trader with monthly bookkeeping and MTD: £600 to £1,200 per year
  • Limited company, annual accounts and return: £800 to £1,500 per year
  • Limited company with monthly bookkeeping, payroll, and CIS reconciliation: £1,200 to £2,400 per year

These are rough guides. A proper quote depends on your specific circumstances. We provide fixed fee quotes after a short call to understand your business.

Common Mistakes Construction Subcontractors Make With Their Taxes

Here are the ones we see most often.

  • Not registering for CIS. If you start subcontracting and do not give your UTR to the contractor, they deduct 30%. You can backdate registration, but you lose the money for months.
  • Using the wrong VAT flat rate. Many subcontractors stay on the old 9.5% rate when they should be on 16.5% under the Limited Cost Trader rules. HMRC can backdate penalties.
  • Not keeping mileage logs. HMRC accepts business mileage claims, but only with a proper log. Without one, they can disclaim the entire amount.
  • Mixing personal and business van use without adjustment. If you use your van for personal journeys, you need to account for the private use element. HMRC will look at this in an enquiry.
  • Filing self assessment late. This triggers an automatic £100 penalty, plus daily penalties if you delay further. And you lose the right to claim your CIS refund for that year.
  • Not claiming capital allowances on tools and equipment. The Annual Investment Allowance (AIA) gives you 100% tax relief on most plant and machinery up to £1,000,000 per year. If you buy a digger or a new set of power tools, claim it.

How We Help Construction Subcontractors

At Holloway Davies, we work with construction subcontractors across the UK. Sole traders running their own crew. Limited company directors working through agencies. Partnerships running multi-trade businesses. Every shape.

Our accountant for construction subcontractors service covers:

  • CIS registration and verification support
  • Monthly CIS deduction reconciliation
  • VAT registration and flat rate scheme advice
  • IR35 status reviews and contract reviews
  • Self assessment and corporation tax filing
  • CIS refund claims
  • MTD for ITSA setup and ongoing compliance
  • Bookkeeping using Xero, FreeAgent, or QuickBooks
  • Payroll for any employees you take on

We are ICAEW qualified. That means we are regulated, insured, and held to professional standards. It also means we know how to handle HMRC enquiries if one lands on your desk.

If you are a construction subcontractor and want to stop worrying about CIS deductions and start focusing on the work, get in touch. We will give you a fixed fee quote and a clear plan for the year ahead.