CIS Tax Calculator | Construction Industry Scheme

The Construction Industry Scheme (CIS) is HMRC's tax withholding system for the construction industry. It requires contractors to deduct tax from subcontractor payments and pay it to HMRC monthly. CIS applies to construction work including building, demolition, repairs, decorating, plumbing, electrical work, scaffolding, and site preparation. Both contractors (who manage projects) and subcontractors (who do the actual work) must comply. If you're a contractor spending over £3 million annually on construction, or regularly paying subcontractors, you must register. Subcontractors should register to reduce deductions from 30% to 20%.

To calculate your CIS refund, first add all your CIS income plus any other income (PAYE jobs, private work). Subtract all allowable business expenses to get your taxable profit. Apply the personal allowance (£12,570) and calculate tax at 20% and 40% on remaining profit. Add Class 2 NIC (£179.40 if profits exceed £6,725) and Class 4 NIC (9% on profits £12,570-£50,270, then 2% above). This gives your total tax liability. Subtract all CIS deductions already withheld. If CIS deductions exceed your liability, you get a refund. LOYALS handles this calculation in your Self Assessment for £300 one-off or £50/month with year-round support.

No, this is a common misconception. CIS deductions only count toward your income tax liability. You still owe National Insurance separately when you file your Self Assessment. As a self-employed subcontractor, you'll pay Class 2 NICs (£3.45 per week, £179.40 annually) if your profits exceed £6,725, and Class 4 NICs at 9% on profits between £12,570-£50,270, then 2% on profits above £50,270. Many subcontractors are surprised by the NIC bill at year-end because they thought CIS covered everything. LOYALS includes full NIC calculations and planning in all our CIS packages to avoid surprises.

Construction subcontractors can claim any expenses "wholly and exclusively" for business. Common claims include tools and equipment purchases, van running costs (fuel, repairs, insurance, MOT), business mileage at 45p per mile for first 10,000 miles then 25p, safety equipment and work clothing, trade insurance and professional subscriptions, phone and internet (business portion), accountancy fees, training and qualifications, materials you purchase (not reimbursed), and home office costs using simplified expenses (£6 per week). Keep all receipts as HMRC may request evidence. LOYALS' CIS specialists ensure you claim every allowable expense, often finding deductions previous accountants missed. One client saved £3,200 in their first year just through proper expense planning.

Yes, absolutely. If you don't register for CIS, contractors must deduct 30% from your labor payments instead of 20%. That's an extra 10% of your income withheld unnecessarily. For example, on £40,000 of CIS income, registration saves you £4,000 in cash flow annually. You'll still get this back eventually when you file your tax return, but why let HMRC hold your money interest-free for months? Registration is free and takes 5-10 minutes online. You'll receive a Unique Taxpayer Reference (UTR) which contractors need to verify your status. Even better, aim for gross payment status after 3 years to receive 100% of payments without any deductions.

Payment on account is HMRC's system for collecting tax in advance. If your tax bill (after CIS deductions) exceeds £1,000, you must make two advance payments toward next year's tax: 50% due on 31 January (when you file) and 50% due on 31 July. These are based on your current year's bill, not future earnings. This catches many subcontractors off guard. For example, if you owe £2,000 after CIS deductions, you'll pay £2,000 balance + £1,000 first POA on 31 Jan, then £1,000 second POA on 31 Jul. If your income drops next year, you can reduce POA payments, but must be careful not to underpay or HMRC charges interest. LOYALS manages all POA planning and adjustments in our monthly £50 package.

Yes, many construction workers combine PAYE employment with self-employed CIS work on weekends or evenings. This is completely legal and common. However, your tax gets more complex because both incomes combine for tax purposes. Your PAYE job uses up your personal allowance and basic rate band first, so CIS income may be taxed at 40% if total income exceeds £50,270. If you're a basic rate taxpayer on PAYE but 20% CIS deductions were made on additional income, you'll owe more tax at year-end. Conversely, if you're a higher rate taxpayer, 20% CIS deductions won't cover your 40% liability. LOYALS handles these combined income scenarios daily. Our calculator above accounts for multiple income streams, and our £50/month package includes quarterly planning to avoid year-end shocks.

Penalties escalate quickly. Miss the 31 January deadline by even one day and you'll face: £100 immediate penalty, £10 per day after 3 months (max £900), £300 or 5% of tax owed after 6 months (whichever is greater), another £300 or 5% after 12 months, plus 5% interest on unpaid tax from 1 February. A subcontractor owing £3,000 who's 6 months late could face £1,400+ in penalties and interest. HMRC is unforgiving with construction industry deadlines. If you genuinely couldn't file (serious illness, bereavement), appeal immediately with evidence. Better solution: let LOYALS handle it. We've filed 2,000+ CIS returns with zero missed deadlines. Our monthly £50 package includes deadline tracking, automatic reminders, and guaranteed on-time filing.

Keep all CIS payment statements (sometimes called PDS - payment and deduction statements) for at least 6 years after the tax year they relate to. HMRC can investigate up to 6 years back (20 years if they suspect serious fraud). These statements are critical because they're your only proof of CIS deductions made. Without them, you can't prove tax was already deducted and may be taxed twice. If you've lost statements, contact the contractor immediately - they're legally required to provide copies. If the contractor has disappeared or refuses, contact HMRC's CIS Helpline with as much evidence as possible (bank statements, invoices). LOYALS clients store digital copies in our secure portal, accessible 24/7, so statements never go missing.

No, verification is only required once before the first payment to a new subcontractor. After initial verification, the contractor can rely on that status until HMRC notifies them of a change. However, contractors must verify correctly using the subcontractor's full legal name, UTR, and National Insurance number (for sole traders) or company registration number (for limited companies). The verification response from HMRC confirms whether to deduct 20%, 30%, or 0%. Contractors must keep a record of verification numbers. If a subcontractor's status changes (loses gross payment status, gets registered), HMRC updates the contractor automatically. LOYALS handles all subcontractor verification for contractor clients in our £150/month essential accounting package, eliminating verification errors.

No, materials costs are always exempt from CIS deductions and must be paid in full. Only labor costs are subject to CIS withholding. When invoicing, clearly separate labor and materials: "Labor: £5,000, Materials: £1,500." The contractor deducts 20% or 30% only from the £5,000 labor portion. Materials must be directly incurred by the subcontractor being paid - you can't claim materials purchased by your sub-subcontractors (this changed from April 2021). Contractors must keep evidence of materials claims. If HMRC disputes materials figures during an inspection, the contractor becomes liable for uncollected CIS deductions. Many disputes arise over what qualifies as "materials" versus "labor." LOYALS advises both contractors and subcontractors on proper CIS invoicing to withstand HMRC scrutiny.

Gross payment status (GPS) allows subcontractors to receive payments without any CIS deductions, improving cash flow significantly. To qualify you must meet strict HMRC tests: pass the compliance test (all tax returns filed on time, all tax paid on time for 12 months), pass the business test (turnover £30,000+ for sole traders, £100,000+ for partnerships/companies), and pass the turnover test (at least one of these must be construction-related). You also need three years of trading history on HMRC systems. From April 2024, VAT compliance is included in the test. GPS can be removed immediately if you file late or miss payments. Many subcontractors think they qualify but don't realize one late filing disqualifies them. LOYALS has successfully obtained GPS for 100+ clients and maintained it with our 100% on-time filing record.

At LOYALS, we offer transparent CIS pricing: £300 one-off for Self Assessment preparation, submission, and tax optimization, or £50 per month (£600 annually) which includes everything in the one-off plus year-round support, quarterly planning calls, unlimited advice, HMRC correspondence handling, and payment on account management. For contractors running limited companies, our £150/month essential accounting includes monthly CIS returns, subcontractor verification, annual accounts, Corporation Tax, and director's Self Assessment. No hidden fees, no setup charges, no expensive extras. Compare this to high street accountants charging £500-£800 for basic CIS returns with limited support. We're ICAEW chartered, CIS specialists with 500+ construction clients, extended hours including weekends, and a track record of £500K+ in tax savings for clients.

Yes, HMRC offers simplified expenses for certain business costs, which can reduce admin burden. For home office use, claim £6 per week (25-50 hours), £12 per week (51-100 hours), or £18 per week (100+ hours) instead of calculating actual costs. For vehicles, use mileage rates: 45p per mile for first 10,000 business miles, then 25p per mile thereafter. However, you cannot mix simplified and actual expenses for the same category. For example, if you use mileage rates, you cannot also claim actual van costs like fuel, insurance, and repairs. Most subcontractors benefit from actual costs if they have high van expenses, but simplified expenses work well for those with lower costs or poor record-keeping. LOYALS analyzes which method saves you more tax and can switch methods year-to-year to maximize savings.

If a contractor incorrectly deducts too little CIS (or none at all when they should have), you're still liable for the full tax owed on that income when you file your Self Assessment. HMRC will pursue you, not the contractor, for underpaid tax. This often happens when contractors wrongly classify you as employed rather than self-employed, or don't realize CIS applies to the work. Check your payment statements monthly to verify correct deductions are being made. If you notice errors, raise them immediately with the contractor. You can also report contractors to HMRC if they consistently fail to operate CIS correctly. In your Self Assessment, declare the gross income and explain the situation. You may end up owing significant tax at year-end if no deductions were made. LOYALS has helped dozens of clients resolve these situations with HMRC.