MTD for CIS Contractors: Subcontractor Compliance Guide

If you work in UK construction, as a bricklayer, plumber, electrician, plasterer, roofer, painter, carpenter, or any other trade under the Construction Industry Scheme (CIS), Making Tax Digital (MTD) affects you on top of your existing CIS obligations. From April 2026, self-employed CIS subcontractors with qualifying income over £50,000 must submit quarterly MTD ITSA updates to HMRC in addition to their normal CIS deductions. The threshold drops to £30,000 in April 2027 and £20,000 in April 2028, bringing the vast majority of UK subcontractors into MTD scope.

This is a double compliance burden that most CIS subbies don’t realise yet. You’ll continue having 20% (or 30%) tax deducted at source by contractors, PLUS you’ll need MTD-compatible digital records, quarterly submissions, and a Final Declaration. Getting this right means:

•       Full recovery of overpaid CIS tax deductions (often £2k-£8k/year)
•       Proper claim of van, tools, PPE, and travel expenses
•       Avoiding £400 MTD non-compliance penalties
•       Building evidence for potential Gross Payment Status upgrade

This guide is written by ICAEW chartered accountants who work with UK CIS subcontractors every day. We’ll cover exactly how MTD works alongside CIS, what you need to do, and how to maximise your tax refunds.

Quick CIS Refresher: How the Construction Industry Scheme Works

Before we get to MTD, let’s make sure we’re on the same page about CIS. Under the Construction Industry Scheme, contractors MUST deduct tax at source from payments to subcontractors doing construction work:

Key CIS insight: CIS deductions are NOT your final tax bill — they’re payments on account. At the end of the tax year, you calculate your ACTUAL tax owed based on your profit (income minus expenses), then reconcile against what was already deducted. Many CIS subbies get REFUNDS at year-end because too much was deducted at source.

How MTD Interacts with CIS for Subcontractors

This is where it gets confusing. CIS and MTD are TWO SEPARATE systems that work together:

CIS System (Stays the Same)

•       Contractors deduct tax at source (20%, 30%, or 0%)
•       Contractors file CIS300 monthly returns to HMRC
•       Contractors give you a Payment and Deduction Statement
•       Your CIS deductions get credited to your tax account

MTD ITSA System (New for You)

•       You keep digital records of ALL income and expenses
•       You submit 4 quarterly MTD updates per year
•       You submit an annual Final Declaration
•       At Final Declaration, your CIS deductions are offset against total tax owed

The critical connection: your Final Declaration is where CIS deductions get reconciled with your actual tax bill. If more was deducted than you owe (very common), you get a REFUND. If less was deducted, you owe HMRC the balance.

When Do CIS Subcontractors Need MTD?

MTD ITSA applies to CIS subcontractors based on gross income (turnover), NOT what you take home after CIS deductions:

Reality check for CIS subbies: If you’re on £250-£350/day working 5 days/week, your annual gross income is £62,500-£87,500. You’ll be in the FIRST wave of MTD from April 2026. Don’t wait — start preparing NOW.

What Counts as Qualifying Income for CIS Subcontractors?

It’s your GROSS invoiced amount (before CIS deduction), plus:

•       Any materials you supplied (invoiced separately)
•       Cash-in-hand work (all cash income must be declared)
•       Property/rental income if you own investment properties
•       Other self-employment income (side jobs, weekend work)

What CIS Subcontractors Must Do Under MTD

1. Keep Digital Records of Everything

All income and expenses must be recorded digitally in HMRC-approved MTD-compatible software:

•       Every invoice you issue (with CIS deduction shown)
•       Every contractor’s Payment and Deduction Statement (PDS)
•       Every expense: van fuel, tools, PPE, materials, phone, home office
•       Bank statements linked digitally
•       Cash transactions (must be recorded digitally within reasonable time)

2. Track CIS Deductions Carefully

Every payment you receive from a contractor should come with a Payment and Deduction Statement (also called a CIS payslip). This shows:

•       Total invoiced amount (gross)
•       Materials cost (not subject to CIS)
•       Labour amount (subject to CIS)
•       Tax deducted (20%, 30%, or 0%)
•       Net amount paid to you

Chase every missing statement: If a contractor doesn’t give you a PDS, chase them. Without proper documentation, you can’t claim back your CIS deductions and HMRC may refuse your refund at Final Declaration. This is where most CIS subbies lose money.

3. Submit 4 Quarterly MTD Updates

Every 3 months, submit summary of your income and expenses via MTD-compatible software:

4. Submit Annual Final Declaration

At year-end, submit a Final Declaration by 31 January following the tax year end. This is where the magic happens for CIS subbies:

1.     Total income (all your invoiced work)
2.     Total business expenses (van, tools, PPE, travel, etc.)
3.     Profit = Income – Expenses
4.     Tax owed on profit (based on Income Tax bands + NI)
5.     CIS deductions already made (from contractor PDSs)
6.     Refund or balance owed

Case Study: How We Got a Plumber a £6,800 CIS Refund + MTD Setup

A self-employed plumber in the Manchester area came to us in early 2026, working under CIS for 3-4 main contractors across residential and commercial projects. Annual gross income: ~£72,000. He’d been doing his own Self Assessment badly for years.

His situation:

•       20% CIS deducted at source (registered but not GPS)
•       Only claiming basic expenses (fuel, tools) — missing thousands
•       No proper record of Payment and Deduction Statements
•       MTD deadline (April 2026) approaching — no software
•       Van maintenance, PPE, phone, home office all underclaimed
•       Insurance and public liability never claimed

What we did:

7.     Set up FreeAgent (£15/mo – has excellent CIS module)
8.     Reconstructed all missing Payment and Deduction Statements from bank records
9.     Identified £8,400/yr in unclaimed expenses (van servicing, tool insurance, PPE, phone use, home office, professional insurance)
10. Amended prior 2 tax years, additional £3,200 refund
11. Set up mobile receipt capture (photo receipts on job sites)
12. Applied for Gross Payment Status (approved 6 weeks later)
13. Took over MTD compliance for £85/month all-inclusive

Outcome: Full MTD compliance, plus £6,800 refund from HMRC in year 1 (£3,600 current year + £3,200 amendments), PLUS Gross Payment Status meaning he now gets 100% of invoiced amounts and pays tax annually at Final Declaration. Net cost: £1,020/yr. Net year-1 benefit: £5,780. Ongoing annual benefit: ~£3,600/yr in captured deductions.

Best MTD Software for CIS Subcontractors

CIS subcontractors need software with proper CIS handling — most generic accounting software doesn’t do this well. Recommendations:

FreeAgent is often free! If you bank with NatWest, RBS, Ulster Bank, or Mettle, FreeAgent is 100% free. This makes it the ideal choice for CIS subbies — no monthly software cost, plus excellent CIS handling. Ask us to help you set it up.

Should You Apply for Gross Payment Status (GPS)?

Gross Payment Status means contractors pay you the FULL invoiced amount — no CIS deductions. You then pay your tax at year-end via your Final Declaration. Benefits:

•       Better cash flow (no 20-30% deducted at source)
•       Simpler admin (no chasing Payment and Deduction Statements)
•       Ability to invest cash before tax deadline
•       Preferred by many larger contractors

GPS Eligibility Requirements

You must meet all three tests:

14. Business test: Your work is genuinely construction industry
15. Turnover test: Net construction turnover of £30,000+ (sole trader) or £30,000 per partner/director (partnership/Ltd)
16. Compliance test: You’ve complied with tax obligations for the past 12 months (returns filed, tax paid on time)

MTD makes GPS eligibility easier: Under MTD, your compliance record is digital and clean. Subbies who use MTD software properly for 12+ months build strong compliance records that satisfy HMRC’s GPS test.

6 Common CIS Subcontractor Mistakes Under MTD

Mistake 1: Not Tracking All PDSs

Every payment should come with a Payment and Deduction Statement. Missing PDSs = missing CIS credit = bigger tax bill or smaller refund. Always chase contractors for statements — legally they must provide them.

Mistake 2: Under-claiming Van Expenses

Many CIS subbies claim only 45p per mile — but if you use actual costs (fuel + servicing + insurance + tax + depreciation) you often claim £3k-£6k/yr more. For high-mileage subbies, actual costs win.

Mistake 3: Missing Tool/PPE Deductions

Tools, safety boots, hi-vis, hard hats, gloves, harnesses, drills, saws, extension cords, batteries — all 100% deductible. Many subbies claim only major purchases and miss the accumulating smaller items.

Mistake 4: Not Claiming Home Office

Even if you spend most time on site, you likely use a home office for admin, quotes, invoicing, tool storage. Claim actual proportion of home costs (usually £1k-£2k/yr) instead of flat rate £26/mo.

Mistake 5: Cash Work Not Recorded

Cash-in-hand work MUST be declared — HMRC increasingly targets construction cash economy. MTD’s digital records make this obvious to HMRC. Best practice: bank all cash within 3 days, record in software immediately.

Mistake 6: DIY Tax Without MTD Prep

A £70k gross CIS subbie doing DIY tax is typically losing £3k-£8k/year in unclaimed expenses PLUS facing MTD non-compliance risk. Chartered accountant fees (£800-£1,500/yr) usually deliver 3-5x their cost in captured deductions + refunds.

How CIS Subbies Should Prepare for MTD (Step-by-Step)

6+ Months Before Your MTD Start Date

17. Open a dedicated business bank account (Starling, Tide, Mettle are good)
18. Choose CIS-friendly MTD software (FreeAgent, Xero with CIS app)
19. Start tracking ALL expenses (photograph receipts on phone)
20. Chase and file all Payment and Deduction Statements

3-6 Months Before

21. Connect bank account to accounting software
22. Categorise past 6-12 months of transactions
23. Assess Gross Payment Status eligibility
24. Register for MTD ITSA via HMRC gov.uk

Ongoing After MTD Starts

25. Photo receipts immediately (on job sites)
26. Record CIS deductions weekly (from PDSs)
27. Reconcile bank account weekly
28. Submit quarterly updates within deadline
29. Submit annual Final Declaration by 31 January

MTD for CIS Contractors: FAQs

Does MTD apply to CIS subcontractors?

Yes — MTD ITSA applies to self-employed CIS subcontractors with qualifying income over £50,000 from April 2026, £30,000 from 2027, and £20,000 from 2028. This is IN ADDITION to your existing CIS deductions at source.

Do CIS deductions count toward MTD thresholds?

No — MTD thresholds are based on GROSS income (turnover before CIS deductions). If you invoice £60k gross but receive £48k after 20% CIS deductions, your qualifying income is £60k — putting you in MTD scope from April 2026.

Do I still file CIS300 monthly returns under MTD?

Only if you’re a CONTRACTOR (you pay other subcontractors). CIS300 is filed by the contractor, not the subcontractor. As a subcontractor, you receive Payment and Deduction Statements from your contractors — no CIS300 filing required from you.

What software handles both CIS and MTD?

FreeAgent has excellent built-in CIS module (and is FREE with NatWest/RBS/Mettle banking). Xero requires a CIS add-on app. QuickBooks has limited CIS support. For most CIS subbies, FreeAgent is the best choice.

Can I claim back CIS deductions under MTD?

Yes — CIS deductions are payments on account. At your Final Declaration (31 January), your total tax bill is calculated, and CIS deductions are offset. If more was deducted than owed (very common), you get a refund. If less, you owe the balance.

How do I get Gross Payment Status?

Apply to HMRC via gov.uk. You need: (1) genuinely construction industry work, (2) £30k+ construction turnover (per person for partnerships/Ltds), (3) 12 months of good tax compliance. MTD compliance strengthens your application.

Do I need an accountant as a CIS subcontractor?

Strongly recommended for anyone earning £30k+ gross. Chartered accountants typically save CIS subbies £2k-£8k/year through captured deductions, proper CIS reconciliation, and refund maximisation. Fees usually pay 3-5x back.

What expenses can CIS subbies claim?

Van/vehicle costs (actual OR mileage), tools & equipment, PPE & safety wear, materials (if not billed separately), phone & internet, home office (actual costs), professional insurance, training courses, subcontractor payments, van tax & MOT, breakdown cover.

What if my contractor doesn’t give me Payment and Deduction Statements?

It’s a legal requirement — chase them by email/text. If they refuse, report to HMRC. Without PDSs, you can’t claim CIS credits at Final Declaration. Consider stopping work with non-compliant contractors.

Can I amend previous tax returns to claim missed expenses?

Yes — you have 4 years to amend Self Assessment returns. Many CIS subbies discover thousands in missed expenses when a proper accountant reviews their history. Common recovery: £2k-£8k in refunds from amendments.

What about cash-in-hand work?

Must be declared. HMRC increasingly targets construction cash economy — MTD’s digital records make cash payments obvious when they don’t match declared income. Bank cash within 3 days, record in software immediately.

Do CIS subbies working through umbrella companies need MTD?

If you work through an umbrella company (PAYE), you’re an employee for tax — CIS doesn’t apply, and MTD ITSA doesn’t apply either (umbrella handles all tax). This is different from being a self-employed CIS subbie.

Do Ltd company subcontractors face MTD?

Yes but differently. Ltd company subcontractors have MTD VAT (if registered), MTD Corporation Tax (from ~2027), and the director’s personal MTD ITSA if they have other qualifying income. Company income itself isn’t under MTD ITSA.

What penalties do CIS subbies face for MTD non-compliance?

£400 per non-compliant return, £200 per late submission (after 4 points), up to £3,000 for failing to keep digital records. This is IN ADDITION to any CIS penalties on the contractor side.

Should I switch from sole trader to Ltd company under MTD?

Depends on income level and complexity. Above £45k-£50k profit, Ltd companies can be more tax-efficient (with pension planning). Below that, sole trader is usually simpler. Get chartered accountant advice — the MTD burden is different in each structure.

Maximise Your CIS Refund + Get MTD-Ready — Free ICAEW Review

CIS subcontractors have the biggest untapped tax refund opportunity in UK self-employment. Between missing PDSs, unclaimed van costs, under-claimed tools & PPE, missed home office deductions, and unclaimed professional insurance, most CIS subbies are leaving £2k-£8k+ on the table every year. Add MTD compliance requirements from April 2026, and DIY becomes very risky.

At MTD – Making Tax Digital (part of B1 Accountants), our ICAEW chartered accountants specialise in CIS + MTD for UK subcontractors. We can:

•       Set up CIS-friendly MTD software (often free)
•       Reconstruct missing Payment and Deduction Statements from your records
•       Identify all deductible expenses (typically £3k-£8k+ in captured deductions)
•       Amend previous tax returns for missed refunds (up to 4 years back)
•       Apply for Gross Payment Status when eligible
•       Handle all 4 quarterly MTD submissions
•       Handle annual Final Declaration for maximum refund