UK Publishes Sustainability Assurance Standard Ahead of Mandatory Reporting Decision

The Financial Reporting Council has published the International Standard on Sustainability Assurance (UK) 5000, a new standard for practitioners carrying out assurance engagements on sustainability reporting, as the UK government considers introducing mandatory sustainability disclosure requirements. The standard is available for voluntary use by UK assurance providers and is aligned with the global benchmark standard developed by the International Auditing and Assurance Standards Board.

The IAASB published the finalized global ISSA 5000 standard in November 2024, designed for use across multiple sustainability reporting frameworks including those issued by the EU, ISSB, GRI, ISO and others. The UK version, ISSA (UK) 5000, adapts this for the UK market and has been released ahead of a series of UK government consultations on mandatory sustainability reporting standards, climate-related transition plan requirements and a voluntary registration regime for sustainability assurance providers. The FRC said the standard is intended for voluntary use for now.

The FRC's own research indicated that a majority of sustainability reporting users express concerns about ESG data quality, including the use of outdated or inaccurate data and estimates. By establishing a consistent framework for sustainability assurance, the standard aims to increase the credibility of UK sustainability reports and support more informed investment decision-making. The FRC said the standard also reinforces the UK's attractiveness as a leading destination for sustainable finance.

The release of ISSA (UK) 5000 ahead of mandatory reporting requirements reflects a sequencing strategy in which assurance capacity is built before disclosure obligations become enforceable, reducing implementation risk. For Indian companies with UK market exposure—including dual-listed firms and those with significant UK investor bases—the development of the UK sustainability assurance framework provides advance notice of the quality expectations that will apply to UK-mandated disclosures. India's own SEBI-mandated BRSR assurance requirements for the top 150 listed companies offer a parallel example of this approach.

Key figure — 48% of ESG rating users cited transparency concerns about methodologies and data sources