title: "Your subcontractor's fraud could cost YOU 30% — HMRC changes the rules in 8 days" slug: cis-supply-chain-liability-april-2026 date: 2026-03-29 sector: construction tags: [CIS, HMRC, construction, compliance, gross-payment-status, April-2026] description: From 6 April 2026, HMRC applies the Kittel principle to CIS. If your subcontractor commits fraud and HMRC decides you should have known — you lose Gross Payment Status for 5 years and face a 30% penalty. Here's what every UK contractor needs to know right now.

Your subcontractor's fraud could cost YOU 30% — HMRC changes the rules in 8 days

There's a change coming on 6 April 2026 that most UK contractors haven't heard of. And the ones who find out after the deadline could be looking at a 30% penalty on their tax bill — plus losing their Gross Payment Status for five years.

This isn't a paperwork tweak. This is HMRC shifting legal liability onto you for what your subcontractors do.

What's changing on April 6?

HMRC is applying the "Kittel principle" to the Construction Industry Scheme. The Kittel principle — taken from EU VAT fraud case law — means that if you "knew or should have known" that a transaction was connected to fraud, you are liable.

Previously, the CIS enforcement framework was mainly about your own filings and payments. From April 6, it extends to your supply chain. If a subcontractor you've worked with turns out to have been committing tax fraud, HMRC can now come after you — the contractor — if they determine you should have spotted it.

The question is no longer "did you commit fraud?" It's "did you take reasonable steps to check you weren't facilitating it?"

The stakes are higher than you think

HMRC has budgeted to recover £205 million from this measure in year one. That's not a token enforcement effort — that's a targeted recovery campaign with serious resource behind it.

The penalties are severe:

• 30% of the tax loss — not a fixed fine, but a percentage of what HMRC believes was underpaid
• Loss of Gross Payment Status — previously, GPS could be revoked for 1 year. From April 6, the bar rises to 5 years
• Once you lose GPS, 20% is deducted from all your CIS payments. For many firms, that's enough to make them uncompetitive for contracts. Five years without GPS could end a business.

"I verified them when I hired them" — that's not enough anymore

This is the trap most contractors are walking into.

Many UK construction firms ran a CIS verification when they first engaged a subcontractor. Maybe they checked their registration status, confirmed the UTR, made sure deductions were being applied correctly. They ticked the box.

That box is now insufficient.

HMRC's expanded framework expects ongoing monitoring. If your subcontractor's circumstances changed — if they became non-compliant, if their registration lapsed, if there were signs of fraudulent activity — and you missed it because you only checked once at onboarding, HMRC can argue you "should have known."

The compliance burden has shifted from a one-time check to a continuous process.

NIL returns: the silent penalty trap

Alongside the Kittel changes, April 6 also makes monthly NIL returns mandatory for all CIS contractors — even in months when no payments were made to subcontractors.

Many firms stopped filing NIL returns years ago. It seemed pointless — no payments, no return, no problem. That view is now wrong.

Failing to file a NIL return triggers automatic penalties. Miss enough of them and it's further evidence of poor compliance management — exactly the kind of thing HMRC looks for when deciding whether you "should have known" about fraud in your supply chain.

If you've had quiet months and skipped the NIL returns, you already have a compliance gap that needs fixing before April 6.

Why HMRC is targeting construction now

The construction industry has historically been the sector with the highest CIS non-compliance. HMRC knows it. The £205 million recovery target for year one of the Kittel changes is almost certainly weighted toward construction.

HMRC has been building its data infrastructure for years — matching CIS filings against VAT returns, payroll data, and company accounts. The April 6 changes give them a new legal basis to pursue contractors who were previously considered clean because the fraud was their subcontractor's problem.

That legal protection is disappearing in 8 days.

What you should do right now

1. Audit your active subcontractors. Check their CIS registration is current. Look for red flags: recently changed bank details, unusual invoice patterns, pressure to pay quickly.

2. Set up a verification schedule. Not just on onboarding — monthly or quarterly checks for any subcontractor you use regularly.

3. Check your NIL return history. If you've had months without subcontractor payments and haven't filed, file them now. The penalty clock may already be ticking.

4. Document your due diligence. If HMRC does come knocking, your defence is the paper trail showing you took reasonable steps. "We checked once when we hired them" is not a defence. A record of ongoing monitoring is.

5. Get a monitoring system. Manual tracking across multiple subcontractors is how things fall through the cracks.

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Eight days is not a lot of time. But it's enough to get compliant — if you start today.

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