A CIS tax return is not a separate CIS form. For a subcontractor it is the ordinary tax return of the business — Self Assessment for a sole trader, the payroll and corporation tax filings for a limited company — with the CIS deductions taken from your pay credited against what you owe.

It starts with the payment and deduction statements. A contractor who deducts CIS must give you one within 14 days of the end of each tax month; tax months end on the 5th, so that means by the 19th. Keep every one: they are the evidence for the credit, and a missing statement is a common reason a claim stalls.

For a sole trader the deductions go on the Self Assessment return, due online by 31 January after the end of the tax year, with any tax still owed paid by the same date. For a limited company they are offset through the Employer Payment Summary. Both routes, and why there is so often a refund at the end of them, are below.

A CIS tax refund arises because your contractor deducts 20% from the labour element of every payment without knowing anything about your allowances or costs. For most registered subcontractors, a year of deductions adds up to more than the income tax and National Insurance actually due — and the difference comes back to you once the right return is filed.

Why you are usually over-deducted

• The deduction ignores your £12,570 personal allowance
• It is taken before your tools, van, travel, protective clothing and phone are deducted
• If you started or stopped part-way through the year, a full year’s allowance sits against part of a year’s income
• Unregistered subcontractors suffer 30%, which almost always produces a refund once the return is in

Sole traders: the refund comes through Self Assessment

As a self-employed subcontractor you claim through your Self Assessment return. The deductions on your statements are credited against the tax on your profit, and any excess is repaid. You do not have to wait for the 31 January deadline — the return can go in as soon as the tax year ends on 5 April. Before filing we check your statements against what contractors reported to HMRC, because a mismatch is the most common reason a refund stalls.

Limited companies: offset through the EPS

If you trade through a limited company, CIS deductions are not claimed on a personal return. The company reports them each month on its Employer Payment Summary and offsets them against the PAYE, National Insurance and CIS it owes HMRC itself. Anything left unused at the end of the tax year can then be claimed as a repayment. A company that does not claim the offset monthly pays its payroll taxes in full while HMRC holds its money.

If you engage subcontractors in London, our CIS returns service runs the monthly cycle for you: we verify new subcontractors, calculate deductions on the labour element of each invoice, issue statements, file the return by the 19th and tell you what to pay by the 22nd if you pay electronically. CIS deductions are paid to HMRC together with PAYE and National Insurance from your own payroll, so we run both from the same figures and the payment reconciles.

What we need from you each month is short:

• Subcontractor invoices received, with labour and materials shown separately
• The dates and amounts you paid
• For anyone new, their name, UTR and National Insurance number or company registration number, before you pay them

Gross payment status removes the deduction altogether, so you are paid in full and settle tax through your return. To qualify you pass three tests at a high level: a business test (construction work in the UK, run through a business bank account), a turnover test (labour turnover above HMRC’s threshold, excluding VAT and materials), and a compliance test (returns filed and tax paid on time). It suits established subcontractors with steady profit who are disciplined about setting tax aside. If your profit is modest, the refund route often costs you little, because much of what is deducted comes back.

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• CIS calculator

Your contractor deducts tax at source and hands it to HMRC. Nothing in that process accounts for your personal allowance, your expenses, or the fact that you paid for your own tools and travel. Those only come into it when your self-assessment return is filed — which is why so many subcontractors are owed money.

• Registration with HMRC as a CIS subcontractor, so you are deducted at 20% rather than 30%
• Self-assessment return prepared with every allowable expense claimed
• Refund claim submitted and chased through to payment
• Deduction statements checked against what the contractor actually reported
• Advice on whether incorporating would leave you better off

Keep every deduction statement your contractor gives you. Without them HMRC will not accept the deductions you are claiming credit for, and reconstructing a year of payments from bank entries is slow and expensive.

Running a CIS scheme means verifying every subcontractor with HMRC before you pay them, deducting at the rate HMRC gives you, issuing deduction statements, and filing a monthly return by the 19th. Miss a return and the penalty is £100 immediately, rising with each month it stays outstanding — regardless of whether any tax was due.

We run the whole cycle for you: verification, deduction calculations, statements to your subcontractors and the monthly return to HMRC. If you have fallen behind, we deal with the catch-up filings and argue the penalty position where there is a reasonable excuse to argue.

CIS is not a way of turning an employee into a subcontractor. HMRC looks at how the work is actually controlled, whether the worker can send a substitute, and who carries the financial risk. Getting this wrong is expensive for the contractor, because HMRC will pursue the PAYE and NIC that should have been operated. If you are unsure where a working relationship sits, we will review it before it becomes a problem.

Deduction at source is a cash-flow problem before it is a tax problem. Twenty per cent of every payment is held back for a year, and for a subcontractor with materials and wages to fund, that is the difference between taking work and turning it down.

Gross payment status stops the deduction entirely — you are paid in full and settle the tax through your return. It has to be applied for and it has conditions: turnover above a threshold excluding materials, a business run through a bank account, and a clean compliance history. That last one is where applications fail, and it is the one you can do something about in advance.

It is also lost as well as won. HMRC reviews the status, and a run of late returns or late payments can take it away — which is a much bigger event than the penalties that caused it.

The twenty per cent comes off labour, not off materials. If the invoice does not separate them, the contractor is entitled to apply the deduction to the whole amount — and a great many do, because they have nothing else to go on.

Split every invoice: labour, materials, plant hire. It costs nothing and on a materials-heavy job it changes the deduction substantially. Keep the purchase invoices too, because the figure has to be the actual cost rather than a stated one.

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Most of the CIS material written for the trade is about being paid. The obligations that actually generate penalties belong to the contractor doing the paying, and they run monthly whether or not there is anything to report.

Verify before the first payment

Every new subcontractor has to be verified with HMRC before you pay them, and the verification tells you which rate to deduct — the standard rate, the higher rate for someone not registered, or nothing at all where they hold gross payment status. Guessing is expensive in both directions: deduct too little and the shortfall is yours to make good, deduct too much and you have taken money from someone who has to wait a year to recover it.

The return is due monthly, including nil months

The return covers the tax month to the 5th and is due by the 19th. A month with no payments still needs a nil declaration unless you have told HMRC you are inactive. The penalty for a late return starts immediately and escalates, and because the obligation is monthly a single overlooked period can be repeated a dozen times before anyone notices — which is how a small administrative slip becomes a four-figure penalty.

And you must give the subcontractor a statement

Each subcontractor is entitled to a payment and deduction statement for every month in which you deducted from them. It is what they will use to reclaim. Not issuing them is a breach in itself, and it also guarantees a difficult conversation later when their figures do not match yours.

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The services we provide for construction businesses include personal tax and self-assessment, VAT returns and registration and bookkeeping. Each has its own page with what is included and how we work.