Construction Contractors Risk 5-Year GPS Loss for Supply Chain Fraud Under New CIS Rules

Effective April 6, 2026, a main contractor in the UK construction industry can lose Gross Payment Status (GPS) for five years if HMRC determines they “knew or should have known” fraud was occurring anywhere in their supply chain — even several tiers removed. The updated Construction Industry Scheme (CIS) rules align the deduction scheme more closely with VAT’s Kittel principle, shifting real accountability upward and promising £205 million in additional revenue in the first year.

This is not a theoretical tightening. HMRC has explicitly signaled it will examine whether main contractors took “reasonable steps” to ensure fraud-free supply chains. Previous measures, including the 2021 Domestic Reverse Charge for VAT and stricter GPS tests in 2024, failed to stamp out serious non-compliance. Construction businesses remain disproportionately represented among deliberate defaulters, according to HMRC data released in November 2025.

“The change that will really land with contractors and subcontractors is the new power to cancel gross payment status under the CIS immediately when HMRC believes a business knew or should have known it was involved in a transaction connected to fraud,” said Barbara Bento, partner for tax disputes and investigations at Buzzacott. “Importantly, that can include cases where a business has suspicions about fraudulent activity somewhere in the supply chain but doesn’t act on them.”

What the April 6 Changes Actually Require

The reforms introduce three material shifts:

• Expanded “knew or should have known” test: Contractors and directors can now face transfer of tax liability and penalties reaching 30% of the tax lost. GPS revocation is immediate rather than delayed, with the reapplication ban extended from one year to five years.
• Mandatory nil returns reinstated: Contractors whose businesses include construction operations must submit monthly CIS returns even when no payments were made to subcontractors in the tax month — unless they proactively notify HMRC of inactivity. Late filing penalties will now apply in full.
• Public body exemption formalized: Payments to certain public bodies are removed from the definition of “contract payment,” eliminating unnecessary deductions and reporting on qualifying public sector work.

HMRC’s updated internal manual (CISR80000) outlines expected due diligence: ongoing monitoring of subcontractors, red-flag detection systems, documented evidence of checks, and use of technology for supply chain visibility. Box-ticking exercises will no longer suffice.

The Cash Flow and Compliance Cost Implications

For subcontractors, loss of GPS means 20% or 30% CIS deductions at source — a direct hit to working capital on already thin-margin projects. Main contractors face indirect pressure: strained subcontractor relationships, potential liability for transferred tax debts, and higher administrative burden.

Early estimates suggest thousands of firms will need to upgrade compliance processes. Those already managing VAT reverse charge, IR35, and CIS simultaneously will find the new anti-fraud layer adds meaningful cost — particularly for mid-sized contractors managing dozens of subcontractors across multiple sites.

Firms without centralized subcontractor onboarding, automated verification, or audit-ready records face the highest risk. HMRC has indicated it will push responsibility up the chain, meaning tier-one contractors cannot simply rely on subcontractors’ self-certifications.

Practical Steps Construction Firms Must Take Now

Smart contractors are already moving beyond compliance theater. Recommended actions include:

• Map your full supply chain with documented risk assessments for every subcontractor and material supplier.
• Implement ongoing monitoring rather than one-time checks — monthly or quarterly reviews supported by data analytics where possible.
• Document everything: Retain evidence of red-flag investigations, communications, and decisions. “Should have known” is proven through absence of reasonable steps.
• Train project and finance teams on fraud indicators specific to CIS — from phantom workers to inflated invoices routed through connected entities.
• Review technology stack: Many firms are accelerating adoption of integrated compliance platforms that flag CIS status changes, VAT anomalies, and payment patterns in real time.
• Engage specialists early: Tax advisers recommend fresh health checks of CIS processes before the first post-April monthly return deadline.

The public body exemption offers minor relief for contractors heavily involved in government or local authority work, but the nil return requirement adds friction for smaller or intermittent operators.

Why This Enforcement Shift Matters for UK Construction Accounting Teams

Construction has long been a target for organized tax fraud due to fragmented supply chains, mobile workforces, and cash-intensive operations. By linking CIS compliance to the same “knew or should have known” standard used in VAT cases, HMRC is effectively demanding that financial and compliance teams treat subcontractor vetting with the same rigor as major financial controls.

Accounting and bookkeeping functions will bear much of the load. Monthly returns (including nils), enhanced record-keeping for due diligence defense, and potential liability calculations now require tighter integration between site operations, payroll, and finance systems.

Firms that treat the new rules as an opportunity to professionalize supply chain governance — rather than another compliance checkbox — will reduce risk while potentially improving project margins through better subcontractor performance monitoring.

The clock is running. With the first affected monthly CIS returns due in May, contractors have weeks, not months, to embed demonstrably robust processes. Those who wait for HMRC enforcement action will discover the five-year GPS ban creates far more than a temporary cash flow problem — it can reshape a firm’s entire competitive position in the industry.

The message from HMRC is clear: ignorance or inaction on supply chain fraud is no longer a defense. For construction contractors, stronger compliance is now table stakes for protecting both cash flow and operational freedom.