A CIS deduction shown on a monthly payment statement is not necessarily the final tax you owe. For many construction subcontractors, it is a payment towards their eventual tax bill – and, when the figures have been recorded properly, it can lead to a refund. This CIS tax return guide explains what needs to go on your return, which deadlines matter and how to avoid leaving legitimate money unclaimed.
The Construction Industry Scheme can feel unnecessarily complicated because the term “CIS return” is used for more than one task. Contractors submit monthly CIS returns to HMRC. Subcontractors usually declare their construction income and CIS tax deductions through Self Assessment. Knowing which obligation applies to you is the first step towards staying compliant and keeping control of your cash flow.
CIS tax return guide: know which return you need
If you work as a subcontractor, a contractor will normally deduct tax from the labour element of your payment before paying you. The standard deduction rate is 20% for subcontractors registered with HMRC. It is 30% where the subcontractor has not been verified or registered correctly. Gross payment status is different again: qualifying subcontractors receive payments without CIS deductions but must still account for the income and tax through the proper channels.
As a sole trader, you generally report your construction income and business expenses on your Self Assessment tax return. The CIS deductions already made are entered separately, so HMRC can credit them against your Income Tax and National Insurance liability. If too much tax has been deducted, the calculation may show a repayment.
A partnership must prepare its partnership tax return, while each partner also completes an individual Self Assessment return for their share of the profit. If you trade through a limited company, the position requires more care. The company reports its income and expenses through its company tax return, while CIS deductions suffered can usually be offset against PAYE and National Insurance liabilities through payroll reporting. Directors may also have a personal tax return to complete.
It is possible to be both a contractor and a subcontractor. For example, a growing builder may engage other trades while carrying out work for a larger contractor. In that case, monthly CIS returns for your subcontractors sit alongside your own tax reporting. Keeping these records separate is essential.
Contractor monthly CIS returns
If you pay subcontractors for construction work, you normally need to verify them with HMRC, calculate deductions where required and submit a CIS return each month. The return is due by the 19th of the following tax month. Any tax deducted must generally reach HMRC by the 22nd when paying electronically.
Even if no subcontractors were paid in a month, you may need to submit a nil return unless you have told HMRC that you will not be making payments for a period. Late returns can trigger penalties, so this is an area where a reliable bookkeeping and payroll process saves both time and worry.
Get your income and CIS deductions right
Your monthly CIS deduction statements are central to an accurate Self Assessment return. They should show the contractor’s details, your details, the gross payment, any materials amount, the tax deducted and the date of payment. Keep every statement, rather than relying on bank transactions alone.
Before submitting your return, reconcile the total deductions on these statements to the income recorded in your accounts. A simple spreadsheet can work for a small operation, but digital bookkeeping software is often easier once you have regular jobs, materials, several contractors or a mixture of CIS and non-CIS work.
Do not assume every amount paid into your bank is construction income subject to CIS. You may also have private work, consultancy income, training income or sales of materials. These still need to be declared where taxable, but they should be identified correctly. Similarly, a contractor may deduct CIS from an invoice incorrectly, particularly where materials have not been separated from labour. Raising clear invoices helps prevent disputes and gives you a stronger audit trail.
A deduction statement missing from your records does not automatically mean you cannot claim the tax credit, but it does mean you should investigate before filing. Ask the contractor for a replacement and check that your name, Unique Taxpayer Reference and verification status are correct. Claiming deductions that cannot be supported can delay a repayment or create an HMRC enquiry.
Claim expenses without overstating them
Your tax is based on profit, not turnover. That means you can deduct allowable business costs before calculating what you owe. For a subcontractor, these may include tools and equipment, protective clothing, public liability insurance, accountancy fees, trade subscriptions, a business proportion of your mobile phone and internet costs, advertising, training that maintains existing skills, and vehicle costs for qualifying business travel.
The detail matters. Ordinary clothing is not normally allowable simply because you wear it to work, whereas protective boots, hard hats and branded uniform may be. Likewise, travel between home and a regular permanent workplace is usually treated as commuting. Travel to temporary sites can be allowable, but the answer depends on the facts, including how long you expect to work there and whether you have an established base.
If you buy tools or larger equipment, the relief may be claimed through capital allowances rather than as a day-to-day expense. If you are VAT registered, VAT that you can recover should not normally be included in your expense total. These distinctions affect the figures and are worth getting right, particularly where your costs are substantial.
Keep receipts, invoices and mileage records as you go. HMRC generally expects records to be retained for at least five years after the 31 January submission deadline for the relevant tax year. Trying to rebuild a year’s worth of expenses from a bank statement in January is one of the quickest ways to miss claims and lose valuable time.
Deadlines, payments and possible refunds
The tax year runs from 6 April to 5 April. For Self Assessment, a paper return is normally due by 31 October following the end of the tax year, while an online return is normally due by 31 January. Any balancing tax payment is also usually due by 31 January.
That January payment can be higher than expected because HMRC may ask for payments on account towards the following year’s bill. These are advance payments, normally due on 31 January and 31 July, and are based on the previous year’s liability. CIS deductions already suffered are taken into account, but they do not remove the need to plan for payments on account where your untaxed income or profits have increased.
Where your deductions and allowable expenses exceed your final liability, the return can show a repayment. Do not rush to file using estimates just to obtain it. An accurate return with complete CIS statements and clear records is less likely to be delayed than one that later needs correction.
If you have never completed a Self Assessment return before, you may need to tell HMRC that you need to file by 5 October after the end of the relevant tax year. Leaving registration until the final weeks before the January deadline can create avoidable pressure, especially if you need to retrieve your tax details or resolve verification issues.
Common CIS mistakes that cost subcontractors money
Most costly mistakes are not dramatic. They are small gaps repeated over a year: misplacing deduction statements, omitting cash or private jobs, claiming the full cost of personal phone use, forgetting legitimate insurance or tool costs, or confusing turnover with profit.
Another frequent issue is assuming that 20% CIS deductions settle everything. They may be too high, too low or broadly right depending on your profits, other income and expenses. A subcontractor with modest profits and high legitimate costs may be due money back. Someone with profitable work outside CIS, rental income or other income may have more tax to pay.
Limited company contractors should be particularly cautious about treating CIS deductions as personal tax. The deduction belongs to the company where the company performed the work. The way it is recovered is different from a sole trader’s Self Assessment claim, so company and personal records must not be mixed.
Make your next return easier now
Set aside time each month to save CIS statements, match payments to invoices and record expenses while the job is still fresh. It is a modest habit that gives you better visibility over profit, reduces the chance of a missed deduction and makes decisions about pricing, equipment and cash flow more confident.
If your records have fallen behind, or your work includes a mix of CIS, VAT, payroll and limited company obligations, tailored support can remove much of the uncertainty. Stewart Accounting Services can help construction businesses turn scattered paperwork into accurate accounts and tax reporting – leaving you more time to focus on the next job with greater peace of mind.