CIS | Southall
CIS Tax in Southall: the 30% Trap, Unopened HMRC Letters, and Help in Punjabi, Hindi and Urdu
Southall has one of the largest communities of South Asian construction workers in Britain. Thousands of carpenters, plasterers, groundworkers and electricians from UB1 and UB2 work The Green Quarter, the Park Royal corridor and sites across West London every day. And every year, a painful number of them give HMRC more money than they owe, not because of the tax rules themselves, but because the system only speaks English. This guide explains the two most expensive problems we see in Southall, in plain language, and exactly how to fix both.
Problem one: the 30 per cent trap
When a contractor or agency takes you on, they must check your details with HMRC before paying you. This is called verification. If your details match HMRC's records, they deduct 20 per cent tax from your pay. If the details do not match, or you were never registered properly, they must deduct 30 per cent instead.
That extra 10 per cent is not a fine and it is not lost. But you only get it back by filing a Self-Assessment tax return. We regularly meet Southall subcontractors who have been on 30 per cent for a year or more without realising, because nobody explained what the deduction line on their payment statement meant.
Quick check: look at any payment statement from your contractor. If the deduction is 30 per cent of your labour amount rather than 20 per cent, you are over-deducted right now, and we can recover the difference going back up to four tax years.
Why does verification fail?
- Name spelling differences between your CIS registration and what the contractor submits. This catches out many workers whose names have more than one English spelling.
- Never registered for CIS as a subcontractor, only for Self-Assessment (they are two separate registrations).
- UTR number given incorrectly or mixed up with a National Insurance number.
- Old details from a previous address or a closed business still on HMRC's record.
The fix takes minutes when done properly: register or correct your CIS registration, give every contractor the exact name and UTR that HMRC holds, and check your first payment statement to confirm 20 per cent. We do this for clients as standard before they start any new job.
Problem two: the unopened letters
The second problem costs even more. HMRC writes in formal English: notices to file, penalty warnings, statements. If English is not your first language, the natural response to a frightening official letter is to put it in a drawer. We have sat at kitchen tables in Southall opening two years of unopened HMRC post with clients.
Here is the truth about those letters: most of them are routine, and the scary ones get worse the longer they wait. A £100 late-filing penalty becomes £1,000+ at three months and continues climbing at six and twelve months. Meanwhile, the same person ignoring the letters is usually owed a refund of £1,500 to £5,500, because their CIS deductions overshot their real tax bill.
Two years of letters, £6,800 back
A shuttering carpenter from Southall came to us through his cousin, with fourteen months on the 30 per cent rate and two unfiled returns. We spoke Punjabi through the whole process, fixed his verification, filed both years and recovered £6,800. The unopened letters turned out to contain penalties we successfully appealed, because no tax was actually owed.
What you can claim against your CIS income
Your refund grows with every legitimate expense you claim: van and fuel costs or 55p (up from 45p, from April 2026)-per-mile, tools and blades, PPE and boots, CSCS card renewal, training courses, materials you bought yourself, your phone's business share and more. Most under-claimed returns we rebuild in Southall are missing thousands in expenses. See our step-by-step CIS refund guide for the full list, or try the 60-second refund calculator.
Help in your language
Your Tax Help Accountants works with Southall clients in English, Punjabi, Hindi and Urdu. We read every HMRC letter with you and explain what it actually says, we deal with HMRC directly as your registered agent so you never sit on hold, and our Stanmore office is 8 miles away if you prefer to talk face to face. Everything starts with a free 15-minute call, in whichever language you think in.
More about our local service: CIS accountant in Southall.
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Frequently Asked Questions
I have been deducted 30 per cent for months. Is that money gone?
No. Every pound deducted under CIS is credited against your tax bill when you file a Self-Assessment. The over-deduction comes back as part of your refund, and we can amend or file up to four previous tax years to recover older amounts.
Can someone else deal with HMRC for me?
Yes. Once we are appointed as your agent (a quick authorisation HMRC posts to you), we speak to HMRC on your behalf, file your returns, and receive copies of correspondence. You never have to call them yourself.
My friend does my tax return but I do not know what he claims. Should I worry?
You are legally responsible for your own return, even if a friend filed it. If you do not know what was claimed, it is worth a professional review: we regularly find both missed refunds and risky claims in informally-prepared returns. A review costs nothing at the initial call stage.
Do I need to come to an office?
No. Most Southall clients send us photos of statements and receipts by WhatsApp and we handle everything online. But the Stanmore office is there if you want to sit down with a person, and many first-time clients prefer that for the first meeting.
How do I register for CIS properly in the first place?
Two registrations matter: Self-Assessment (which gives you your UTR) and CIS subcontractor registration (which links that UTR to the construction scheme so contractors verify you at 20 per cent). Many Southall workers have the first but not the second. Registration is free, done with HMRC directly, and we handle both for new clients as standard, including making sure the name HMRC holds exactly matches your documents.
I am paid partly in cash for weekend jobs. Does that go on the return?
Yes. All self-employed income belongs on your return, cash included. Declaring it is rarely as expensive as people fear, because your expenses and the CIS deductions from your main work usually cover most or all of the tax. Not declaring it is how small problems become HMRC investigations.
How quickly will my refund arrive once you file?
We file within 24 to 48 hours of receiving complete records, and HMRC typically pays refunds 4 to 6 weeks after filing. File in April or May and the money lands before the summer; the worst option is waiting until January when HMRC is slowest.
Is my information safe if I send documents on WhatsApp?
We treat WhatsApp photos as a convenient way for you to get documents to us, then store everything in our secure systems. Your details are never shared or sold, and as a registered agent practice we are bound by confidentiality and data protection rules. If you prefer, you can hand documents over in person at the Stanmore office.
Stuck on 30 per cent, or sitting on unopened HMRC letters?
Bring them to us this week. Free 15-minute call in English, Punjabi, Hindi or Urdu, and an honest answer about what you are owed and what it costs to fix.
Or email info@yourtaxhelp.co.uk | CIS accountant in Southall
General guidance only. Not personal tax advice. Contact us for advice specific to your situation. Figures relate to the 2025/26 tax year unless otherwise stated.