CIS Materials Vs Labour Split , Getting The Deduction Right
- Atlas Tax
- 6 hours ago
- 15 min read
CIS Materials vs Labour Split: Getting the Deduction Right
Under the Construction Industry Scheme, the CIS deduction applies only to the labour element of a payment, not to the direct cost of materials the subcontractor has genuinely purchased and incorporated into the work. Get the split wrong and the contractor either over-withholds (damaging the subcontractor's cash flow and the working relationship) or under-withholds (leaving the contractor personally liable to HMRC for the shortfall, plus interest). The rule is straightforward in principle and routinely misapplied in practice.
How the Deduction Is Actually Calculated
The calculation follows a two-step process under section 61(1) Finance Act 2004.
Start with the gross payment due, excluding any VAT charged by the subcontractor. Then remove the qualifying materials figure. What remains is the amount subject to CIS deduction: either 20% for a registered subcontractor, or 30% for one that is unregistered. A subcontractor with gross payment status receives everything without deduction.
So for a registered subcontractor submitting an invoice with labour of £3,000 and qualifying materials of £800 (ex-VAT), the calculation is:
● Gross: £3,800
● Less qualifying materials: £800
● Sum subject to deduction: £3,000
● CIS deduction at 20%: £600
● Net paid to subcontractor: £3,200 (plus any VAT, paid in full)
The subcontractor receives £3,200 plus the VAT element in full. The contractor pays £600 to HMRC as an advance against the subcontractor's income tax and Class 4 NIC, and then accounts for the remaining balance to the subcontractor.
That is the mechanics. The difficulty lies almost entirely in determining what counts as qualifying materials.
What Qualifies as Materials (and What Does Not)
The Direct Cost Rule
HMRC's position, set out at CISR15060, is that the deductible materials figure is the direct cost to the subcontractor: what they can demonstrate they actually paid for materials used in carrying out that specific construction contract. Mark-up does not qualify. Profit margin does not qualify. If a subcontractor purchases bricks for £600 and invoices the contractor for £800 under the materials heading, only £600 is deductible for CIS purposes. The £200 excess is treated as part of the taxable labour payment.
This is a point that surprises some subcontractors when they first hear it. The materials exemption is not intended as a means of sheltering profit on supplies; it exists to ensure that a genuine cost already incurred by the subcontractor is not taxed twice. HMRC expects evidence, and in practice a contractor who cannot produce purchase invoices or receipts to back up a materials figure is carrying a risk.
The materials must also relate specifically to the contract under which payment is being made. You cannot aggregate purchases across multiple jobs and apply them loosely to whichever invoice happens to be raised next.
Plant Hire: Hired vs Owned
This is one of the most frequently misunderstood areas of CIS, and one I see causing problems regularly among trades clients across Greater Manchester, particularly in groundworks, demolition, and specialist fit-out where significant plant is involved.
The rule, drawn from CISR15090, depends on whether the subcontractor owns the plant or has hired it from a third party.
Where a subcontractor has hired plant from a third party, the cost of that hire may be treated as materials for CIS purposes. Any consumable items used in operating the hired plant, including fuel, may also be treated as materials.
Where the subcontractor owns the plant themselves, no notional hire figure can be claimed as materials. The plant cost is simply part of running their business. However, and this is the one exception, consumable items such as fuel used by owned plant may still be treated as materials.
So on a practical invoice, if a groundworker hires a telehandler from a local plant company and passes that cost on at direct cost, it qualifies. If they own the telehandler, none of the equipment cost qualifies (only the fuel consumed by it).
This distinction matters enormously. A subcontractor who owns a fleet of plant and routinely shows those assets as a materials line on their invoices is likely over-claiming, which creates a compliance exposure for the contractor who accepts those figures without checking.
What Is Definitely Not Materials
Several items are routinely included on invoices but do not qualify as materials for CIS:
● Travel to and from site, including fuel for the subcontractor's own van
● Accommodation near the site
● Waste removal and skip hire
● Insurance
● Tools and equipment owned by the subcontractor
● Consumables such as drill bits, blades, or tape that form part of the subcontractor's general overhead rather than being directly incorporated into the works
These items may well be legitimate business expenses that the subcontractor claims on their Self Assessment return (or, from 2026/27 for those with turnover above the MTD for Income Tax threshold, through quarterly digital reporting). But they are not materials for the purpose of calculating the CIS deduction.
The Contractor's Obligation (and the Liability That Comes With It): Who Bears the Risk if the Split Is Wrong
Regulation 4(3)(b)(iii) of SI 2005/2045 places the responsibility squarely on the contractor to verify that the materials figure on a subcontractor's invoice is accurate and not overstated. This is not optional and not transferable.
If HMRC investigates and finds that the contractor accepted inflated materials figures without any supporting evidence, the contractor will face a demand for the under-deducted CIS tax, together with interest. Penalties may also follow. The fact that the subcontractor provided incorrect information is a partial mitigation but not a complete defence, particularly where the contractor made no attempt to check.
The practical upshot is that for any significant materials claim, the contractor should request copies of purchase invoices. HMRC's published guidance, CIS340, states explicitly that the contractor must check and keep records to confirm that the materials portion is not overstated. This is not something buried in an obscure manual; it is in the guidance document that every contractor operating CIS should be familiar with.
There is a limited concession available under Regulation 9(5) of SI 2005/2045 where the contractor acted in good faith and took reasonable steps to verify the position. HMRC may apply this to reduce or offset the liability. But relying on that concession as a strategy rather than simply checking materials claims is poor compliance practice.
Monthly Returns: The New Nil-Return Rule from April 2026
One change that took effect from 6 April 2026 is worth flagging here. Mainstream contractors are now required to submit a monthly CIS return for every tax month, even where no payments have been made to subcontractors. Previously, a contractor could appeal a nil-return penalty automatically in certain circumstances. That route is no longer available. The return must be filed, or a period of inactivity must be pre-notified to HMRC before the relevant month begins.
For contractors who work seasonally or take on subcontract labour only for specific projects, this requires a change in administrative habit. Missing a monthly return now generates a penalty that cannot easily be reversed.
Worked Example: A Mixed Invoice
The following example is representative of the kind of invoice that regularly causes confusion in practice.
A plastering subcontractor, CIS registered at the standard 20% rate, submits an invoice for a residential refurbishment job:
Line Item | Amount |
Labour | £2,400 |
Plasterboard and beads (purchased, receipts available) | £680 |
Hired mixer and pump (hired from local plant company) | £220 |
Own tools | £0 (not charged) |
Travel to site | £90 |
3 nights accommodation | £180 |
Mark-up on materials (10%) | £68 |
Total (ex-VAT) | £3,638 |
Working through the CIS calculation:
● Labour: £2,400 (subject to deduction)
● Qualifying materials: £680 (direct cost, evidenced) + £220 (third-party hired plant) = £900
● Travel, accommodation, mark-up: not qualifying; treated as part of taxable payment
● Effective taxable amount: £2,400 + £90 + £180 + £68 = £2,738
● CIS deduction at 20%: £547.60
● Net paid to subcontractor: £3,638 less £547.60 = £3,090.40 (plus VAT in full)
If the contractor had simply taken the invoice at face value and applied the deduction only to the labour line of £2,400, the deduction would have been £480. The difference, £67.60, represents an under-deduction for which the contractor would be liable if HMRC examined the return.
Conversely, if the contractor had applied the deduction to the entire £3,638 without separating out qualifying materials, the deduction would have been £727.60: an over-deduction of £180 from the subcontractor's legitimate materials costs.
Neither error is harmless.
What Subcontractors Should Do
From the subcontractor's side, the practical answer is clear: invoice in a way that makes the split obvious and supportable. Keep your purchase receipts for materials used on each specific job, because if your contractor asks for them you are obliged to provide evidence. Distinguish between materials you have bought and passed on at cost versus any mark-up, because only the former qualifies.
If you include travel or accommodation as a separate line, understand that you may receive less than the full amount. The contractor is not wrong to apply the deduction to those items. If you want to recover those costs without a CIS deduction being applied, the answer is to gross up your labour rate to reflect them, rather than presenting them as separate qualifying costs.
Making Tax Digital for Income Tax Self Assessment came into force on 6 April 2026 for sole traders and landlords with qualifying income above £50,000. If you are a CIS subcontractor above that threshold, you are now submitting quarterly updates to HMRC, and your digital records should separately categorise labour income and materials in order to reconcile correctly with the CIS payment and deduction statements issued by your contractors. Getting this distinction right in your bookkeeping from the outset avoids a correction exercise at year-end.
New Compliance Risks from April 2026: Sections 62A and 62B
The Finance (No. 2) Bill introduced two new provisions, sections 62A and 62B, that take effect from April 2026 and which have a direct bearing on the materials versus labour question. These extend HMRC's ability to pursue liability through the supply chain where payments or returns were made with knowledge, or where there should have been knowledge, that a failure was occurring somewhere in the chain.
The practical consequence for contractors is that processing an inflated materials claim from a subcontractor, particularly where a pattern of such claims exists or where the contractor failed to check, now carries a greater enforcement risk than before. HMRC can look further up and down the chain when it identifies deliberate or careless non-compliance in the split.
This is not a purely theoretical concern. CIS compliance reviews increasingly flag inconsistencies in labour and materials splits as a primary trigger for a wider investigation. A contractor whose CIS300 returns show systematically high materials ratios relative to the nature of the work being described is more likely to receive scrutiny.
Key Points
The materials exemption under CIS applies only to the direct cost the subcontractor can demonstrate they actually paid for materials used in that specific contract, not to mark-up, accommodation, travel, or costs relating to other contracts.
Owned plant does not qualify as materials, though fuel used by owned plant does. Third-party hired plant qualifies at direct cost.
The contractor is responsible for checking that materials claims are accurate, and carries the liability for any under-deduction if those checks are not made.
From 6 April 2026, all mainstream contractors must file a monthly CIS return for every tax month, including nil periods, or pre-notify HMRC of inactivity. The previous automatic appeal route for nil-return penalties has gone.
The new sections 62A and 62B now allow HMRC to pursue liability more broadly through the supply chain where there was knowledge of, or failure to detect, a misstatement. This increases the compliance stakes for anyone accepting subcontractor invoices without scrutiny.
Invoice clearly, keep your evidence, and check the split every time.
FAQs
Q1: If a subcontractor does not split their invoice into labour and materials, what should the contractor do?
A1: Well, it is one of those situations that comes up more often than you would think, particularly with smaller trades who have never been asked to invoice in a particular way before. The short answer is that the contractor cannot simply guess at a split and hope for the best. The obligation sits squarely with the contractor under Regulation 4(3)(b)(iii) of SI 2005/2045: if materials are to be excluded from the CIS deduction, the contractor must be satisfied the figures are accurate and not overstated.
In practice, the safest course is to go back to the subcontractor and ask them to reissue or itemise the invoice before payment. If they genuinely cannot or will not do this, the contractor should apply the deduction to the full gross amount (ex-VAT) and treat the entire payment as labour. That is a conservative position, and the subcontractor may not like it, but the alternative, applying a notional materials split without any supporting evidence, leaves the contractor holding the liability if HMRC later disagrees. Some contractors take the view that for a small, regular subcontractor doing labour-intensive work, the risk is minimal. That may well be true, but it is a risk the contractor is taking, not the subcontractor. Always confirm with HMRC or your accountant if you are unsure of the right treatment for your specific arrangements.
Q2: Can a subcontractor claim the cost of scaffolding they have hired in as materials for CIS purposes?
A2: This is a genuinely interesting edge case that does not get discussed nearly enough. The answer depends on whether the scaffolding hire is subsidiary to a main supply of materials or whether it is essentially a service in its own right.
The general rule under CISR15090 is that plant hired in from a third party by the subcontractor can be treated as materials for CIS purposes, provided the cost is passed on at direct cost. Scaffolding hired from a scaffolding company to enable construction work to proceed could, in principle, qualify on this basis.
However, there is a real distinction between scaffolding as incidental support for a supply-and-fix operation (where the subcontractor is supplying and fixing materials and needs the scaffold to do so) versus a specialist scaffolding subcontractor who is simply being paid to erect and dismantle the structure. In the latter case, the payment is more accurately characterised as a labour-based construction service, and the CIS deduction applies to the full amount.
Consider a roofing subcontractor in Greater Manchester who hires a scaffold to replace tiles on a terrace of houses. The scaffold hire is enabling a supply-and-fix job and could reasonably be included in materials at direct cost. A specialist scaffold company hired directly by the main contractor to erect a scaffold is in a different position entirely. The distinction matters, and if the figures involved are significant, it is worth getting a clear view before your next CIS300 is filed.
Q3: What happens if a contractor has been over-deducting CIS from a subcontractor's materials for several months?
A3: In my experience, this is one of the most awkward situations to unwind, partly because it involves repaying money that has already been passed to HMRC, and partly because it can damage the relationship with the subcontractor.
The position is relatively straightforward in principle. CIS deductions that were taken in error from qualifying materials amounts should not have been deducted in the first place. The contractor has over-withheld, which means the subcontractor has received less than they were entitled to. The excess deductions will have been reported on the contractor's CIS300 returns and paid to HMRC.
The contractor cannot simply pay the subcontractor the difference from their own funds and then ignore the HMRC position; the CIS returns would be incorrect. The contractor should amend the relevant CIS300 returns through HMRC's online system to correct the materials and deduction figures. Any over-payment to HMRC arising from the correction can then be offset against future CIS liability or reclaimed. The subcontractor receives the corrected net payment.
Where the subcontractor is self-employed, the over-deducted amount would eventually have come back to them via their Self Assessment return anyway, but that is cold comfort if it has affected their cash flow for months. Getting the invoicing right at source prevents all of this. Ensure subcontractors know to itemise clearly, and if you have any doubt about a materials claim, ask for the receipts before paying rather than after.
Q4: Does the domestic reverse charge for VAT change how the materials and labour split is calculated under CIS?
A4: The domestic reverse charge (DRC) and CIS are two separate regimes that operate alongside each other, and they are frequently confused. It is a common mix-up, but here is the important distinction: the DRC changes how VAT is handled on the invoice, but it does not alter the CIS calculation at all.
Under the DRC, which has applied to most construction services between VAT-registered businesses since March 2021, the subcontractor does not charge VAT on their invoice. The contractor accounts for the VAT directly on their own VAT return. However, CIS still applies in exactly the same way. The contractor excludes qualifying materials from the gross payment and applies the deduction rate (20% or 30%) to the remainder, just as they would on any other CIS invoice.
One nuance worth noting: for a VAT-registered subcontractor, the CIS base is calculated on VAT-exclusive amounts. So if a subcontractor who is VAT registered lists materials on their invoice, you exclude VAT from the materials figure when working out the deductible amount. If the subcontractor is not VAT registered, the VAT they paid on materials forms part of their direct cost and is included in the qualifying materials figure (since they cannot reclaim it).
Keep the two calculations separate in your records. The DRC affects your VAT return; CIS affects your CIS300 return and the net amount you pay your subcontractor. They run in parallel, not in conflict.
Q5: If a main contractor supplies materials to a subcontractor free of charge, can the subcontractor still claim a materials deduction on their invoice?
A5: No, and this is a point that catches people out. The rule is clear: the materials deduction is based on the direct cost to the subcontractor. Where the main contractor has provided materials free of charge, known as free-issue materials, the subcontractor has incurred no cost whatsoever. There is nothing to deduct.
The purpose of the exemption is to ensure the subcontractor is not taxed on a cost they have already borne. If they have not borne the cost, the rationale for the exemption falls away entirely. A subcontractor who invoices for a materials figure when the materials were supplied by the contractor is, in effect, misrepresenting the basis of the claim.
Consider a joinery subcontractor fitting bespoke units on a high-end Manchester city centre development where the developer has provided all the cabinetry. The subcontractor's invoice should show labour only. If they add a materials line for the cabinets they did not pay for, the contractor cannot legitimately exclude that from the CIS base.
Where a job involves a mixture of contractor-supplied and subcontractor-supplied materials, only the subcontractor's actual purchases qualify. Keep records of what was and was not free-issued, as HMRC compliance reviews increasingly ask for this documentation.
Q6: Can a subcontractor operating through a limited company claim back CIS deductions during the tax year, or do they have to wait until the end?
A6: This is one area where operating through a limited company gives a real cash flow advantage over being a sole trader, provided the company is set up to take advantage of it.
A limited company subcontractor can offset CIS deductions suffered against the company's PAYE and National Insurance liabilities each month. The process works through the Employer Payment Summary (EPS), which is submitted via PAYE Real Time Information. Each month, the company reports the cumulative CIS deductions it has suffered, and HMRC reduces the company's PAYE/NIC payment due accordingly. If the CIS deductions in a given month exceed the PAYE liability, the excess carries forward to the following month. Anything remaining at the year end can be offset against Corporation Tax on the CT600, or reclaimed directly.
A sole trader, by contrast, generally cannot recover CIS deductions until they file their Self Assessment return. The full amount of deductions suffered sits with HMRC until the return is filed and processed, which for most people means waiting until the return is submitted after 5 April. That can represent months of deferred cash.
The practical implication is significant. A subcontracting company suffering £2,000 per month in CIS deductions could recover that in real time if they have sufficient PAYE liabilities to offset. Without the EPS process set up correctly, that same company might wait until well into the following tax year to see the money. If your accountant is not setting up EPS offsets for your limited company, it is worth asking why.
Q7: Is there a safe way for a contractor to estimate the materials element when a subcontractor provides a lump-sum invoice rather than an itemised one?
A7: There is no officially sanctioned method for estimating the split, and HMRC's guidance is quite clear that the contractor must be satisfied the materials figure is accurate, not guessed. That said, in practice, contractors do face situations where the split is genuinely unclear, and HMRC recognises that a reasonable good-faith estimate is preferable to applying the deduction to the full amount where materials are obviously present.
The key phrase there is good faith and reasonable. If you are paying a supply-and-fix tiling contractor and you have a reasonable basis for believing that a certain proportion of the payment represents materials they purchased, applying a conservative estimate and keeping a note of your reasoning is better than ignoring the issue. What you should not do is apply an inflated materials figure based on nothing more than a hope that it will reduce the deduction. That creates a direct risk under the contractor liability rules.
Some contractors ask subcontractors to provide a proportional breakdown at the start of the contract (for example, that materials represent approximately 40% of the agreed contract value) and use that as the basis for subsequent progress payments. HMRC will look more favourably on a consistent, documented approach than on a different split on every invoice with no explanation. Keep the evidence of what you agreed and why. If HMRC ever queries the returns, your position is much stronger with a paper trail than without one. Always confirm the approach with your accountant if the values involved are significant.
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