Construction Industry Scheme (CIS) Tax Explained

Summary

CIS exists because HMRC found that the construction industry had high levels of unpaid tax in the 1970s and 80s. The Inland Revenue created CIS to require contractors to deduct tax at source before paying subcontractors, eliminating the gap between earning and HMRC collection. CIS has evolved through three major iterations; the current scheme dates from 2007.

The scheme has three roles: contractor (the party paying for construction work), subcontractor (the party doing the work and being paid), and deemed contractor (a non-construction business with construction spend above £3 million in 12 months). Every tradesperson should understand which role they fall into for each job — a sole trader working under another builder is a subcontractor; the same trader hiring a labourer for two days is a contractor for that day.

This guide covers what CIS is, who must register, the deduction mechanics, the monthly return process, verification, gross-payment status, common errors, and the interaction with Self Assessment and VAT reverse charge. For broader business setup see business bank account setup and cis construction industry scheme.

Key Facts

• CIS standard deduction rate — 20% (verified subcontractor)
• CIS higher deduction rate — 30% (unverified subcontractor)
• CIS zero rate — 0% (gross-payment status subcontractor; very high turnover)
• What's deducted — labour cost only; NOT materials, plant hire, fuel, or VAT
• Return filing deadline — 19th of each month (covers previous month's payments)
• Penalty for missed return — £100 immediate + £200 after 2 months + £300+ after 6 months
• Payment to HMRC — 22nd of each month (electronic; 19th if paying by cheque)
• Annual Self Assessment — subcontractor reconciles CIS deductions against income tax liability
• HMRC pays refund — common; subcontractor's deducted tax often exceeds final liability
• Gross payment status (GPS) thresholds — turnover ≥£30,000 (sole trader) or ≥£200,000 (partnership/limited company); plus compliance history
• Scheme administration — HMRC's CIS Online Service via Government Gateway
• Construction operations definition — Section 74 Finance Act 2004; includes most building, alteration, decorating, demolition, installation
• Excluded operations — manufacture/delivery of materials only, signwriting, professional services (architects, surveyors), carpet fitting, scaffolding without erection on site
• VAT reverse charge for construction — since March 2021; complicates CIS interaction
• Deemed contractor threshold — non-construction business spending ≥£3 million on construction in 12 months
• VAT — separate scheme; CIS deduction is BEFORE VAT (deduct from labour element of net of VAT amount)

Quick Reference Table

Detailed Guidance

Who Is a "Contractor"?

Under CIS, you are a contractor if:

• Your business is construction (you do construction work for clients AND hire subcontractors), OR
• You are a "deemed contractor" — a non-construction business (e.g. a major retailer, landlord) spending ≥£3 million on construction in any 12-month period

Most self-employed tradespeople become contractors when they hire labour. A plumber working alone is a sole trader subcontractor; a plumber hiring a labourer for a day becomes a contractor for that work and must register.

Registration is online via HMRC's CIS Online Service. You receive a 13-character contractor reference. Penalty for failure to register: tax penalties plus liability for the deduction you should have made.

Who Is a "Subcontractor"?

A subcontractor is anyone (sole trader, partnership, limited company) doing construction work for a contractor — typically a builder, but increasingly a deemed contractor too. Registration is online via HMRC's CIS Online Service.

When a subcontractor first works for a contractor:

1. Subcontractor provides UTR (Unique Taxpayer Reference, 10 digits)
2. Contractor verifies the subcontractor with HMRC online — instant response confirming the deduction rate (20%, 30%, or 0%)
3. Each payment thereafter has the verified rate applied

If the verification returns 30% (unverified or higher-risk subcontractor), the subcontractor must contact HMRC to update their records or accept the higher deduction.

The Deduction Mechanics

The deduction is from the labour portion of the invoice only. Materials, plant hire, fuel, VAT and travel are NOT deducted from.

Example: Subcontractor invoice:

• Labour: £1,000
• Materials: £500
• VAT (on the whole): £300 (at 20%)
• TOTAL: £1,800

CIS deduction (at 20%): £1,000 × 20% = £200

Subcontractor receives: £1,800 - £200 = £1,600

Contractor pays HMRC: £200 by 22nd of following month

This is why labour cost MUST be clearly separated on a CIS invoice. If the invoice doesn't distinguish, the contractor must deduct on the whole amount (treating it all as labour) — costly for the subcontractor.

The Monthly Return (CIS300)

Each month, the contractor files a CIS300 return covering:

• All subcontractors paid that month
• Each subcontractor's labour and materials amounts
• Each deduction amount
• Total deduction to be paid to HMRC

Filing deadline: 19th of the month after the payment month. Penalty for late filing: £100 immediate; £200 if 2 months late; £300+ if longer.

The return is online via HMRC's CIS Online Service. Most accounting software (Xero, QuickBooks, FreeAgent) integrates with HMRC's API to auto-file.

Payment & Deduction Statement (CIS302)

The contractor must give each subcontractor a Payment & Deduction Statement (sometimes called a "CIS voucher") within 14 days of the end of the tax month. The statement shows:

• Contractor's name and address
• Subcontractor's name and address
• Payment date
• Gross payment (labour + materials)
• Materials value
• Net labour amount
• Deduction amount
• Deduction rate

Subcontractors keep these statements for their Self Assessment.

Gross Payment Status (GPS)

A subcontractor can apply for GPS — receiving payments without any CIS deduction. To qualify:

• Business test — operate a business in the UK and pass HMRC's standard business checks
• Turnover test — annual labour turnover ≥£30,000 (sole trader) or ≥£200,000 (partnership/limited company)
• Compliance test — comply with all tax obligations for the past year (Self Assessment filed on time, payments up to date, etc.)

GPS is held for an initial year, then reviewed. Loss of GPS (e.g. one late tax return) returns the subcontractor to 20% standard. Reinstatement is possible after compliance restored.

GPS is valuable because:

• Cashflow: subcontractor receives the full payment immediately, doesn't wait for refund
• Simplified accounting: no deduction reconciliation
• Customer confidence: GPS-status subcontractors are viewed as more reliable

Self Assessment Reconciliation

At year-end (5 April), the subcontractor files Self Assessment showing:

• Total income (all payments received from all contractors)
• Allowable expenses (materials, plant, mileage, etc.)
• Net profit
• Income tax due on net profit
• Total CIS deducted in the year

The CIS deducted is treated as a payment on account. If the total deducted exceeds the income tax liability + Class 2/4 NICs, HMRC refunds the difference.

Many self-employed tradespeople have deduction ≥ liability, so they receive HMRC refunds annually — sometimes £500–£3,000+ depending on income and allowances.

VAT Reverse Charge Interaction (since March 2021)

For VAT-registered B2B construction invoices (NOT end-user contracts):

• Subcontractor's invoice shows VAT calculation but VAT amount is NOT charged
• Customer (contractor) accounts for VAT on the subcontractor's behalf in their own VAT return
• CIS deduction still applies on labour, regardless of VAT reverse charge

This complicates the calculation. For a VAT-registered subcontractor's labour:

• Labour: £1,000
• Materials: £500
• VAT reverse charge: £0 (customer accounts)
• CIS deduction: £1,000 × 20% = £200
• Subcontractor receives: £1,500 - £200 = £1,300

End-user transactions (the final customer for the building) are NOT subject to VAT reverse charge — normal VAT applies. CIS still applies.

Common Errors

• Forgetting to verify subcontractors — defaults to 30% deduction (subcontractor unhappy)
• Deducting from materials — illegal; refund subcontractor
• Late CIS300 return — automatic penalty
• Not issuing P&D statement — subcontractor can't reconcile Self Assessment
• Failing to register as contractor — penalty plus liability
• Confusing CIS deduction with VAT reverse charge — different mechanisms; both apply on the same transaction
• Not noting "end user" status — VAT reverse charge applies to B2B in the supply chain, not the final end user

Frequently Asked Questions

Do I have to register for CIS if I'm a sole trader doing only my own work?

Only as a subcontractor (when working for other contractors). You don't need to register as a contractor if you don't hire any subcontractors yourself. Most domestic plumbers, electricians, decorators registering as subcontractor only.

What if my customer is a homeowner, not a contractor?

The end-user / homeowner is NOT a contractor under CIS. They don't deduct anything from your payment. Your full payment arrives; you handle the tax through Self Assessment.

Can I claim CIS deductions back if I'm a limited company?

Limited companies that ARE contractors can offset CIS deductions made FROM their own payments AGAINST CIS deductions they OWE to HMRC. This is via the CIS suffered claim on the Employer Payment Summary (EPS) — a different mechanism from sole trader refund.

What happens if HMRC doesn't refund my Self Assessment?

If you've overpaid (CIS deducted > tax + NIC due), HMRC must refund. Refunds are typically processed within 8–12 weeks of Self Assessment filing. If no refund after 12 weeks, contact HMRC. The refund is usually sent to the bank account registered on your Self Assessment.

Does CIS apply to construction professionals like architects?

No. Professional services (architects, surveyors, structural engineers) are excluded from CIS even when contracted by a builder. CIS applies to "construction operations" defined in S.74 FA 2004 — primarily physical work on a building.

What if I sometimes do contractor work, sometimes subcontractor work?

You can be both, on different projects. Register in both capacities. Each invoice (in either direction) needs the appropriate CIS treatment.

Regulations & Standards

• Finance Act 2004 Sections 57–77 and Schedule 11 — primary statutory framework for CIS

• Income Tax (Construction Industry Scheme) Regulations 2005 (SI 2005/2045) — operational regulations

• VAT Notice 735 (Construction reverse charge) — VAT reverse charge guidance

• HMRC's CIS340 — comprehensive HMRC guidance manual

• Construction Act 1996 (Housing Grants, Construction and Regeneration Act 1996) — note: separate Act for payment terms in construction contracts; not CIS

• Limitation Act 1980 — 4 years for recovery of unpaid CIS

• HMRC: Construction Industry Scheme — a guide for contractors and subcontractors

• GOV.UK: CIS Online Service (sign in)

• GOV.UK: Register for CIS as a contractor

• GOV.UK: Register for CIS as a subcontractor

• GOV.UK: VAT reverse charge for construction services

• Finance Act 2004 ss.57–77

• cis construction industry scheme — companion CIS overview

• business bank account setup — CIS-friendly bank setup

• vat registration — VAT and reverse charge

• sole trader vs limited company — choosing the right entity

• expenses allowable self employed trades — Self Assessment allowable expenses