A curated reference of the primary legislation, HMRC guidance, case law, and professional sources that govern reasonable care and “knew or should have known” liability in the Construction Industry Scheme.
This page is maintained by the Tax Radar team and updated as new guidance or case law is published. If you spot something missing, contact us and we will add it.
A note on linking out
We publish this page because the law and guidance behind the April 2026 CIS changes are public, and contractors defending themselves under the new regime should be able to read the source material directly. We are not a substitute for legal advice. Where a specific issue affects your business, consult a qualified tax adviser or solicitor.
The statutory framework for the new CIS regime sits in the Finance Act 2004, as amended by the Finance Act 2026. The pre-2026 framework remains relevant for historical periods and for terms that were not amended.
For consolidated current text, legislation.gov.uk is the canonical source.
HMRC’s published guidance is the primary public statement of how the rules are administered. The Guidelines for Compliance series is particularly important because it sets out HMRC’s expectations of reasonable care in specific sectors.
The internal HMRC manuals are public and set out, in detail, how HMRC officers approach individual issues. They are not law, but they are the strongest available indication of how a case will be handled in practice.
The “knew or should have known” test originates in case law and now appears on the face of the statute at s.62A(1)(b) FA 2004. The cases below built the test that the statutory words carry. The cases below are the foundation of the test that construction will now be judged against. Most are available in full on BAILII.
Construction-specific case law on the new s.62A/62B framework is still emerging. We will list cases here as they are decided and reported. For background on construction tax disputes, the First-tier Tribunal (Tax) decisions database is searchable.
The professional bodies below publish guidance, hold technical updates, and run forums where CIS reform is actively debated. They are useful references for contractors, advisers, and procurement teams alike.
CIS reform is being covered actively in the trade press. The titles below are the ones most commonly read by procurement, finance, and supply chain leaders in UK construction.
For analysis from the Tax Radar team on how these rules apply in practice:
This page is for information only. It is not, and does not purport to be, legal or tax advice. The inclusion of an external source does not constitute endorsement of that source.
Last reviewed: 19 July 2026
CIS Defence implements the due diligence framework set out in GfC12 and refined by the Kittel case law — continuously, automatically, and with a documented audit trail.