Guides, analysis, and reference material on the April 2026 CIS regime, the “knew or should have known” standard, and what defensible compliance looks like in practice. Built for procurement directors, finance directors, accountants, and the advisers who support them.
Construction has been a strategic enforcement priority for HMRC's Fraud Investigation Service for over a decade. The April 2026 reforms are the next step in a fifteen-year arc, not a one-off legislative event. The strategic context for the new regime.
Read the articleQuick Reference
Plain-English answers to the questions contractors are asking. Thirty-eight questions on the April 2026 changes, reasonable care, Gross Payment Status, director liability, subcontractor verification, and how Tax Radar fits in.
Go to the FAQEvery technical term used in the new regime, defined in working English. Forty-one terms across CIS, case law, supply chain risk indicators, and the Tax Radar methodology.
Go to the GlossaryPrimary legislation, HMRC guidance, and the case law construction will be judged against. The original sources behind the rules, gathered in one place.
Go to the Compliance ReferencesGuides and Analysis
A comprehensive guide to the new CIS fraud measures coming into effect in April 2026, what they mean for principal contractors, and how to prepare. The starting point if you are new to the new regime.
By Jack Sloggett.
Read the guideThe “knew or should have known” standard now in CIS was not invented for CIS. It is a VAT principle with nearly twenty years of UK case law behind it. These six cases tell construction contractors what HMRC will do next.
By Jack Sloggett.
Read the articleHMRC has been extending joint and several liability across the tax code for two decades. From 6 April 2026, construction contractors are formally in scope under sections 62A and 62B of the Finance Act 2004. The strategic context for the new regime.
By Jack Sloggett.
Read the articleConstruction has been a strategic enforcement priority for HMRC’s Fraud Investigation Service for over a decade. The April 2026 reforms are the next step in a fifteen-year arc, not a one-off legislative event. The structural drivers behind why the new regime exists.
By Jack Sloggett.
Read the articleHow HMRC tests reasonable care, and how contractors lose. The George Star Builders ruling explained.
By Jack Sloggett.
Read the articleWhy anomaly detection outperforms checklist-based CIS due diligence, and what “reasonable care” looks like under the Finance Bill 2025-26 in software terms.
By Josian Quintana Arroyo.
Read the articleWhat HMRC’s CIS verification covers, what it doesn’t, and why the new regime requires both.
By Jack Sloggett.
Read the articleIn the Press
Construction Enquirer reports on the new CIS fraud legislation effective from April 2026. The article features Tax Radar director Jack Sloggett’s analysis of the “knew or should have known” test and how HMRC can now hold principal contractors responsible for fraud committed elsewhere in their supply chain.
Construction Enquirer.Tax Radar director Jack Sloggett joined HardHats to discuss the new CIS fraud legislation taking effect from April 2026. The conversation covers what the “knew or should have known” test means in practice for construction contractors, how HMRC’s new powers to immediately withdraw Gross Payment Status will work, and the practical steps contractors can take now to protect their businesses.
HardHats.Jack Sloggett, co-founder of Tax Radar, breaks down the April 2026 CIS fraud legislation changes and what they mean for tax advisers and their clients. Published in Tax Adviser, the monthly journal of the Chartered Institute of Taxation.
Tax Adviser Magazine.See It in Action
The most useful conversation we have with a contractor is not the one where we describe the new regime. It is the one where we run their actual supply chain through CIS Defence and show them how their current position would survive contact with it.
This page is designed as a working navigation surface for live Tax Radar guidance, reference material, and press coverage on the April 2026 CIS regime.