ESG Assurance Companies in London: Firms and Services Guide (2026)
AC
Acumon Chartered Accountants·12 min read
This practical guide looks at companies offering ESG assurance services in London, rather than ranking them from first to last. The selection includes larger companies with broad audit, sustainability, and assurance capabilities as well as more focused specialists working with specific ESG disclosures, metrics, and reporting requirements. Each company differs in the types of clients it serves, the scope of assurance it covers, and the wider expertise available around sustainability reporting and controls. The aim is to give enough context to compare these companies on relevant strengths and decide which type of support fits the organisation’s reporting and assurance needs.
Acumon
Acumon is a UK firm of chartered accountants and registered auditors providing ESG assurance services to companies, charities, regulated organisations, and international corporate groups.
The firm works with organisations at different stages of ESG reporting maturity, from businesses preparing their first structured sustainability disclosures to larger groups already reporting environmental, social, and governance information to investors, lenders, customers, and other stakeholders. ESG assurance engagements focus on the reliability of reported information and the evidence, calculations, processes, and controls supporting it.
Acumon provides independent limited assurance over selected ESG metrics and disclosures. The scope can include greenhouse gas emissions, energy consumption, workforce information, and governance statements, with assurance procedures examining the underlying data and the way each reported figure has been produced.
The firm also carries out ESG assurance readiness reviews for organisations that are not yet prepared for formal external assurance. These reviews assess data ownership, reporting processes, documentation, and internal controls, helping identify gaps that need to be addressed before selected disclosures are independently assured.
Carbon and energy reporting forms another part of the ESG assurance service. Acumon reviews matters such as emission factors, estimation methods, reporting boundaries, and consistency between reporting periods, including information prepared in connection with Streamlined Energy and Carbon Reporting requirements.
For international groups, ESG information may be collected across several subsidiaries, business units, and jurisdictions. Acumon’s wider audit experience with corporate groups supports engagements where sustainability information needs to be consolidated from different parts of an organisation while maintaining consistent reporting methods and evidence.
ESG Assurance Capabilities
Acumon provides assurance and readiness services across a range of ESG reporting areas.
These include:
Independent limited assurance over selected ESG metrics and disclosures
Greenhouse gas emissions reporting
Energy consumption reporting
Workforce and social data
Governance statements and disclosures
ESG reporting readiness reviews
Sustainability data and controls assessments
Carbon and energy reporting methodology reviews
SECR-related reporting reviews
Assurance work focuses on the information selected for external reporting and the processes, evidence, and controls supporting those disclosures.
Regulatory Licences and Registrations
Acumon operates as a registered and authorised audit practice, providing a regulatory and quality-control framework for its wider assurance work.
These include:
ICAEW registered audit practice
FRC authorisation for Public Interest Entity audits
Jersey Recognised Auditor status
Isle of Man Recognised Auditor status
These registrations support assurance and audit work for UK organisations, regulated entities, and corporate groups with operations extending into relevant international jurisdictions.
Core Services
In addition to ESG assurance, Acumon provides services covering audit, reporting controls, governance, risk, and sustainability-related reporting.
These include:
ESG assurance
Sustainability reporting assurance
ESG assurance readiness reviews
Carbon and energy reporting reviews
SECR methodology reviews
ESG data and controls assessments
Statutory external audit
Public Interest Entity audits
Group and subsidiary audits
Internal audit and governance reviews
Risk management and compliance support
ESG assurance engagements can be performed as standalone assignments or considered alongside statutory audit where appropriate and subject to applicable independence requirements.
Many organisations begin strengthening ESG reporting when sustainability information becomes more important to investors, lenders, customers, regulators, or corporate group reporting.
Acumon works with businesses that are:
Preparing their first formal ESG or sustainability disclosures
Reviewing carbon and energy reporting methodologies
Responding to lender or supply-chain ESG information requests
Strengthening reporting controls and data ownership
Consolidating ESG information across corporate group structures
Early readiness work can help identify weaknesses in documentation, calculations, responsibilities, and controls before an organisation moves into a formal assurance engagement.
Address: 1-2 Craven Road, Ealing, London, W5 2UA, UK
Deloitte UK
Deloitte provides sustainability assurance through its UK Audit and Assurance practice. Their teams perform assurance over sustainability metrics and disclosures under standards including ISAE 3000 and ISAE 3410, with engagements available at limited or reasonable assurance levels. The subject matter can extend from greenhouse gas emissions to workforce, diversity and other non-financial indicators.
Their assurance capabilities extend to sustainability-linked finance, including verification related to sustainability-linked KPIs, impact reporting and certain green, social and transition financing arrangements. Deloitte also supports organisations as ESG reporting processes mature and the scope of independently assured disclosures expands.
Reporting areas: Environmental, social, workforce and governance information
Location: London and wider UK
Contact Information
Website: www.deloitte.com
Phone: +44 (0)20 7936 3000
Address: 1 New Street Square, London, EC4A 3HQ, United Kingdom
LinkedIn: www.linkedin.com/company/deloitte
Facebook: www.facebook.com/deloitteuk
Twitter: x.com/deloitteuk
Instagram: www.instagram.com/deloitte_uk
KPMG UK
KPMG UK provides independent sustainability assurance for organisations seeking external conclusions over ESG metrics and disclosures. Their work can be delivered at limited or reasonable assurance level under ISAE (UK) 3000, depending on the scope, reporting maturity and stakeholder requirements.
The firm also provides assurance readiness engagements before formal external assurance. These reviews examine whether sustainability reporting processes, supporting evidence and controls are sufficiently developed and can be useful when an organisation introduces new ESG data or expands the scope of an existing reporting programme.
PwC UK delivers ESG assurance as part of its wider non-financial assurance practice. Their work combines sustainability subject-matter knowledge with assurance procedures designed to determine whether reported ESG information is supported by appropriate evidence and reporting processes.
The scope can include sustainability and carbon reporting as well as social information such as diversity and inclusion disclosures. PwC also provides third-party and regulatory assurance, making the practice relevant where ESG information forms part of a broader non-financial reporting and controls environment.
Reporting areas: Sustainability, carbon, social and workforce information
Approach: Independent review of ESG reporting and supporting evidence
Additional capability: Third-party assurance
Location: London and wider UK
Contact Information
Website: www.pwc.co.uk
Phone: +44 (0)20 7583 5000
Address: 1 Embankment Place, London, WC2N 6RH, United Kingdom
LinkedIn: www.linkedin.com/company/pwc-uk
Facebook: www.facebook.com/PwCUK
Instagram: www.instagram.com/pwc_uk
EY UK
EY provides sustainability reporting and assurance services covering non-financial disclosures, ESG metrics and sustainability reports. Independent procedures can support either limited or reasonable assurance and may address information prepared under a range of sustainability reporting frameworks.
Potential assurance areas include ESG KPIs, integrated reports, greenhouse gas inventories, environmental claims, sustainability-related communications and green or social financing. EY also performs ESG pre-assessments covering data, reporting criteria, systems and controls before an organisation moves into formal assurance.
Additional capability: Reporting controls and readiness assessment
Location: London and wider UK
Contact Information
Website: www.ey.com
Phone: +44 20 7951 2000
Address: 1 More London Place, London SE1 2AF
LinkedIn: www.linkedin.com/company/ernstandyoung
Facebook: www.facebook.com/EY
Twitter: x.com/EYnews
Forvis Mazars UK
Forvis Mazars provides independent ESG assurance over sustainability information, data, targets and corporate disclosures. Their UK methodology supports engagements under ISAE (UK) 3000 and ISAE 3410, while the firm’s current sustainability offering also references ISSA 5000 for applicable assurance work.
Engagements can cover environmental, social and governance disclosures, corporate responsibility reporting and specific sustainability KPIs. Both limited and reasonable assurance are available, while pre-assurance services help organisations assess data quality and controls before an external conclusion is issued. The firm has sustainability assurance leadership based in London.
BDO UK has a dedicated ESG Readiness and Assurance practice covering the processes and controls behind non-financial reporting as well as external assurance over disclosed metrics. Their work includes pre-assurance readiness reviews, ESG internal audit assessments and independent limited assurance.
The firm provides limited assurance opinions under ISAE 3000 and ISAE 3410. Its broader sustainability practice covers areas such as carbon reporting, governance, ESG reporting, sustainable finance and supply-chain matters, allowing assurance engagements to be considered alongside wider reporting requirements where appropriate.
Key Facts
Core services: ESG assurance, ESG readiness reviews, internal control reviews
Assurance standards: ISAE 3000, ISAE 3410
Assurance level: Limited assurance
Reporting focus: ESG metrics and control frameworks
Additional capability: Sustainability and ESG advisory
Location: London and wider UK
Contact Information
Website: www.bdo.co.uk
Phone: 020 7486 5888
Address: 55 Baker Street London, W1U 7EU, United Kingdom
LinkedIn: www.linkedin.com/company/bdo-llp
Instagram: www.instagram.com/bdo_uk
Grant Thornton UK
Grant Thornton UK provides ESG assurance within its broader audit and assurance practice. The firm has dedicated ESG assurance expertise and has addressed limited and reasonable assurance, ESG data capture and controls, ISAE 3000 engagements and assurance over narrative as well as quantitative sustainability reporting.
The firm’s sustainability work also addresses the implications of CSRD and the assurance requirements attached to sustainability reporting under the European regime. Grant Thornton has a major London office at Finsbury Circus alongside its wider UK network.
Key Facts
Core services: ESG assurance, audit and assurance, sustainability reporting support
Assurance context: Limited and reasonable assurance
Relevant standard: ISAE 3000
Reporting focus: ESG information, KPIs, processes and controls
Crowe UK combines sustainability consulting with independent assurance over sustainability disclosures. Their published work covers limited assurance, emissions verification, sustainability-linked loan reporting and assurance associated with public sustainability reporting.
Their approach also includes readiness assessments for organisations entering external assurance for the first time. These reviews can test data capture, controls and reporting preparedness before a full limited assurance engagement proceeds. Crowe’s UK sustainability leadership is based in London.
Additional capability: Sustainability reporting and internal controls
Location: London and wider UK
Contact Information
Website: www.crowe.com
Phone: +44 (0)20 7842 7100
Address: 55 Ludgate Hill, London, EC4M 7JW
LinkedIn: www.linkedin.com/company/crowe-uk
Twitter: x.com/CroweUK
Instagram: www.instagram.com/crowe_uk
Price Bailey
Price Bailey provides ESG assurance through its Audit and Assurance practice, including work for companies seeking independent verification of environmental, social and governance disclosures. Their assurance procedures examine data capture, calculations, reporting frameworks and the processes supporting published ESG information.
Limited and reasonable assurance are both addressed within the service. Price Bailey also works with private equity-backed businesses where investors or portfolio reporting requirements create a need for independently assured ESG metrics. The firm’s ESG assurance capability includes specialists working from its City of London office.
Key Facts
Core services: ESG assurance, audit and assurance, ESG advisory
Assurance levels: Limited and reasonable
Reporting areas: Environmental, social and governance metrics
Client context: Private companies, international groups, PE-backed businesses
Moore Kingston Smith provides ESG assurance within a wider sustainability and advisory practice. Their teams issue assurance reports under ISAE 3000 and ISSA 5000, using a risk-based process that covers scoping, materiality assessment, data verification and validation before an assurance report is issued.
The firm also provides climate and sustainability reporting, ESG strategy, greenhouse gas calculations and sustainability due diligence. This combination can be relevant for companies that need to develop their ESG reporting processes before moving specific datasets or disclosures into independent assurance.
Menzies provides independent ESG assurance covering sustainability data, performance metrics and reporting disclosures. Their service includes verification of carbon emissions and energy information, sustainability reporting reviews, governance assessments and analysis of weaknesses within ESG reporting processes.
They also provide limited assurance over carbon footprint information and support reporting connected with frameworks and requirements such as SECR and CSRD. Menzies has an ESG and sustainability team operating from its City of London office, alongside additional UK locations.
Saffery combines sustainability reporting and advisory work with assurance over ESG metrics. Its sustainability specialists support organisations with carbon accounting, transition planning, reporting requirements and the development of ESG data and governance processes.
The firm’s sustainability team includes professionals who perform assurance services on ESG metrics, while its London-based specialists advise organisations preparing for evolving UK sustainability reporting and assurance requirements. This makes the service relevant to organisations that need both reporting preparation and independent scrutiny of selected sustainability information.
Address: 71 Queen Victoria Street, London EC4V 4BE, UK
LinkedIn: www.linkedin.com/company/saffery
Instagram: www.instagram.com/saffery_uk
HaysMac
HaysMac provides ESG assurance through its Risk Assurance and Advisory Services practice. Their ESG work includes assurance aligned with ISAE 3000, focused on adding independent credibility to ESG disclosures and reports.
The firm can also assess ESG frameworks, processes and reporting controls, alongside examining how changing sustainability requirements affect an organisation’s disclosures. This creates a route from initial ESG assessment through reporting improvement to independent assurance over selected information.
Choosing an ESG assurance company in London depends on business size, sector, the maturity of reporting processes, and the regulatory requirements that apply. Some companies combine assurance with broader sustainability reporting, controls, governance, and regulatory support, while others concentrate on narrower areas such as selected ESG metrics, emissions data, or specific disclosures. The right choice should provide credible independent assurance while also identifying practical steps that can reduce reporting risks and strengthen organisational resilience. This guide is intended to give neutral context for comparing different approaches and narrowing the search to companies that match specific assurance requirements. There is no single model that suits every organisation, so the scope and depth of support should remain central to the decision.
AC
Written by the Acumon team
Acumon is an ICAEW-registered firm of chartered accountants and registered auditors
based in London, with offices in Pitstone, Aylesbury and Bournemouth. Need advice on
anything covered here? Talk to us.
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