From Voluntary to Mandatory: The UK Regulatory TrajectoryFor much of the past decade, Scope 3 emissions reporting in the UK has occupied an awkward middle ground: strongly encouraged, widely recognised as important, but ultimately voluntary, but that is changing with notable speed. The Streamlined Energy and Carbon Reporting (SECR) framework, which has applied to large UK companies since 2019, requires disclosure of Scope 1 and 2 emissions alongside energy use and an intensity metric in annual reports. Scope 3 data remains voluntary under SECR but strongly recommended for companies whose value chains generate significant indirect emissions. This means the majority of their carbon footprint in most sectors.The more consequential development is the publication, on 25 February 2026, of the finalised UK Sustainability Reporting Standards (UK SRS) S1 and S2 by the Department for Business and Trade. Based on the International Sustainability Standards Board's IFRS S1 and S2, these standards are currently available for voluntary adoption. However, the direction of travel towards mandatory application is unambiguous as the Financial Conduct Authority launched Consultation Paper CP26/5 on 30 January 2026, proposing that listed companies be required to report in line with UK SRS from accounting periods beginning 1 January 2027. For finance directors and audit committees, this is not a future consideration. Organisations whose data, governance structures, and internal controls are not audit-ready before mandatory requirements arrive will face both regulatory exposure and the reputational consequences of being seen to scramble. Building that foundation now, whilst reporting remains voluntary, is the lower-risk path.The EU Framework: A Non-Negotiable Baseline for Businesses Trading Across BordersFor any UK business with trading relationships in Europe, the EU regulatory framework adds a further and immediate layer of obligation. The EU Corporate Sustainability Reporting Directive (CSRD) and the EU Corporate Sustainability Due Diligence Directive (CSDDD) together require large companies, including non-EU companies with significant EU revenues, to report in detail on ESG performance and to conduct due diligence across their value chains. Critically, CSRD mandates Scope 3 emissions disclosure and applies a double-materiality lens, requiring disclosure both of how sustainability issues affect financial performance and of how the company's activities affect people and the planet. This is broader than the UK SRS financial-materiality approach, meaning companies operating across both jurisdictions face genuinely different reporting obligations from the same underlying data.The financial stakes are most directly visible in the EU Carbon Border Adjustment Mechanism (CBAM), which completed its transition period in 2024. CBAM places a carbon price on imports of iron and steel, aluminium, cement, fertilisers, electricity, and hydrogen, targeting the emissions embedded in the production process itself. For any UK company sourcing or exporting these materials across the EU border, the carbon intensity of the supply chain is now a direct cost factor. The Scope 3 Data Gap: Ambition Without the Infrastructure to Support ItAgainst this backdrop of converging regulatory pressure, the state of Scope 3 data quality across organisations remains a material concern. Sphera's 2025 Scope 3 Report reveals that 79% of companies already reporting on greenhouse gas emissions now disclose across all three scopes, up from just 52% in 2024, yet 62% internal data quality as a major barrier, and 79% say obtaining supplier data remains a top challenge.The significance of this gap is financial as well as reputational. Under UK SRS S2, material Scope 3 categories must be disclosed alongside direct emissions, and those disclosures must be explicitly linked to financial performance and climate risk assessments. Inconsistent or estimated Scope 3 data will not withstand the scrutiny of mandatory assurance. For listed companies preparing for 2027 compliance, and for their supply chain partners who will face increasing data requests as a consequence, the lead time to build reliable, traceable, assurance-ready emissions data is already running short.Sustainability Teams Cannot Close This Gap ManuallyThe challenge is structural as much as it is technical. Sustainability teams in most organisations remain small and overstretched: a handful of employees managing ESG reporting, supplier engagement, emissions accounting, and regulatory monitoring simultaneously. As reporting obligations multiply and assurance requirements raise the bar on data quality, the expectation that these teams can manually collect, validate, and disclose Scope 3 data across complex, multi-tier supply chains is no longer feasible. Yes#ESGData #SustainableFinanceSimon ThompsonVP Northern EuropeJAGGAER28 May, 2026