Internal Audit Outsourcing Companies in the UK: A Practical Guide
AC
Acumon Chartered Accountants·16 min read
For many organisations, maintaining an effective internal audit function is becoming increasingly challenging. Growing regulatory expectations, evolving risks and the need for specialist expertise often make it difficult to resource every requirement internally. As a result, many businesses, charities and public sector organisations choose to outsource all or part of their internal audit activities.
The UK market offers a wide range of internal audit outsourcing providers, from global professional services firms to independent advisory practices with specialist sector expertise. Each brings a different approach, whether the focus is governance, regulatory compliance, operational controls, technology risk or strategic assurance.
This guide provides an overview of selected companies offering internal audit outsourcing services in the UK. Rather than ranking providers, it aims to help organisations understand the range of options available, the services commonly offered, and the types of clients these firms typically support. Whether you're reviewing your existing internal audit arrangements or exploring outsourcing for the first time, having a clear view of the market can make it easier to identify a provider that aligns with your governance objectives, risk profile and organisational needs.
Acumon
Acumon is a UK firm of chartered accountants and advisors providing internal audit outsourcing services to organisations across the UK.
The firm works with organisations ranging from growing businesses and charities through to corporate groups and regulated organisations. Internal audit outsourcing services are designed to provide independent assurance while supporting governance, risk management and internal control frameworks.
Acumon provides internal audit outsourcing services as part of its wider governance and risk advisory offering. Engagements are tailored to an organisation's operational structure, regulatory environment and internal assurance requirements, providing independent reviews of processes, controls and governance arrangements.
Acumon holds a Public Interest Entity (PIE) audit licence, enabling the firm to support organisations subject to enhanced regulatory oversight in the United Kingdom. In addition to its UK statutory audit registration, the firm also maintains audit licences in the Cayman Islands, British Virgin Islands (BVI), Jersey and Isle of Man. These licences enable the firm to support organisations operating across multiple jurisdictions.
Many organisations choose to outsource their internal audit function to obtain independent assurance, access specialist expertise and support effective governance without maintaining a dedicated in-house internal audit team. Outsourced internal audit services can help organisations evaluate risks, strengthen controls and support regulatory compliance.
Acumon works with boards, audit committees, senior management and finance teams to support internal audit requirements while helping organisations strengthen governance arrangements, risk management processes and internal controls.
Internal Audit Outsourcing Capabilities
Acumon provides internal audit outsourcing services across a wide range of organisational structures and sectors.
These include:
UK companies and corporate groups
regulated organisations
charities and not-for-profit organisations
owner-managed businesses and growing companies
UK subsidiaries of international groups
organisations operating across multiple jurisdictions
Internal audit outsourcing engagements are typically led by experienced professionals with direct involvement throughout the engagement.
Regulatory Licences and Registrations
Acumon holds several audit registrations that enable it to support organisations operating across multiple jurisdictions.
These include:
UK statutory audit registration
Public Interest Entity (PIE) audit licence
Jersey audit licence
Isle of Man audit licence
Cayman Islands audit licence
British Virgin Islands audit licence
These registrations allow the firm to support organisations operating across both the UK and key international financial centres.
Core Services
In addition to internal audit outsourcing services, Acumon provides a range of services that support governance, risk management and financial reporting.
These include:
internal audit outsourcing services
governance and internal control reviews
statutory external audit
group and subsidiary audits
Public Interest Entity (PIE) audits
charity and not-for-profit audit
internal audit and governance reviews
risk management and compliance support
Internal audit work is often delivered alongside discussions with management and boards regarding governance arrangements, risk management frameworks and organisational controls.
Many organisations seek outsourced internal audit support as governance requirements evolve, regulatory expectations increase and business operations become more complex.
Acumon works with organisations that are:
expanding business operations
strengthening governance frameworks
managing regulatory obligations
operating across multiple jurisdictions
preparing for future growth
Early engagement can help ensure that governance arrangements, internal controls and assurance activities remain aligned with organisational objectives and regulatory expectations.
Address: 1-2 Craven Road, Ealing, London, W5 2UA, UK
Phone: 020 8567 3451
Bishop Fleming
Bishop Fleming offers internal audit and risk assurance services to organisations across the UK, supporting both public and private sector bodies through outsourced and co-sourced internal audit arrangements. Their approach covers everything from individual reviews of key controls to full internal audit programmes, depending on the size, structure and governance requirements of the organisation. Alongside assurance work, they look at how risk management, governance and internal controls operate in day-to-day practice.
Their internal audit activity is closely linked with wider risk advisory services, giving organisations an independent view of control frameworks and areas where processes may need strengthening. They are involved in sectors where internal audit is often a regulatory requirement, including education, housing, healthcare and government, while adapting the scope of reviews to reflect each organisation's operational risks and assurance priorities.
Key Highlights
Internal audit outsourcing and co-sourcing
Risk assurance and governance reviews
Support for public and private sector organisations
Experience across regulated industries
Internal audit plans and one-off assurance reviews
Focus on governance, risk management and internal controls
Kreston Reeves deliver internal audit outsourcing services for organisations looking to strengthen governance, improve oversight and review how key controls operate across the business. Their work covers corporate organisations, public sector bodies and not-for-profit organisations, with support ranging from fully outsourced internal audit functions to co-sourced arrangements and specialist advisory projects. Assignments are planned around each organisation's objectives, risk profile and regulatory environment.
Alongside core internal audit work, they carry out reviews in areas such as technology, fraud prevention, operational performance and governance. Their team also undertakes external quality assessments, audit committee advisory work and audit transformation projects, helping organisations review how their internal audit function operates while supporting ongoing improvements where needed.
Key Highlights
Complete internal audit outsourcing and co-sourcing
Internal audit advisory and technical support
Experience across corporate, public and not-for-profit sectors
Institute of Internal Auditors aligned methodology
Governance, technology and fraud-focused reviews
External quality assessments and audit committee support
Services
Internal audit outsourcing
Internal audit co-sourcing
Internal audit advisory
External Quality Assessments (EQA)
Governance audits
Technology and IT audits
Fraud reviews and investigations
Audit committee advisory
Contact Information
Website: www.krestonreeves.com
Twitter: x.com/KrestonReeves
LinkedIn: www.linkedin.com/company/kreston-reeves
Address: 2nd Floor, 168 Shoreditch High Street, London, E1 6RA
Phone: +44 (0)20 7382 1820
Grant Thornton
Grant Thornton delivers internal audit outsourcing services as part of their wider business risk offering, supporting organisations that need independent assurance over governance, internal controls and risk management. Their internal audit teams work with businesses in different sectors through outsourced, co-sourced and temporary resource arrangements, allowing organisations to access additional expertise when required. Reviews are designed around each client's assurance needs, with attention given to both established controls and emerging business risks.
One aspect of their approach is the involvement of specialists from different technical disciplines where specific knowledge is needed. This allows internal audit engagements to cover areas beyond financial controls, including operational processes, technology and regulatory change. They also carry out external quality assessments and can provide experienced audit professionals to support organisations facing temporary resource gaps within their internal audit function.
Key Highlights
Internal audit outsourcing, co-sourcing and staff secondments
Focus on governance, risk management and internal controls
Support for organisations across a range of industries
External Quality Assessments (EQA)
Access to specialist risk and technical expertise
Internal audit resource support for in-house teams
BDO approaches internal audit as part of a broader governance and risk framework, helping organisations review how controls, compliance and oversight operate across the business. Their internal audit services are available as fully outsourced or co-sourced arrangements and can also support organisations that already have an in-house audit function. Engagements are planned around each organisation's structure, industry and assurance requirements, with reporting aimed at management, boards and audit committees.
Technology and emerging risks form an important part of their internal audit work. Alongside traditional assurance reviews, they assess areas such as cyber security, data governance, digital transformation and continuous monitoring. Their offering also includes external quality assessments, audit committee support and data analytics, reflecting the wider role internal audit often plays in modern governance.
Henderson Loggie focuses on internal audit outsourcing for organisations looking to strengthen governance, manage risk and review how their control environment operates. Their internal audit team supports clients through outsourced, co-sourced and consultancy engagements, giving organisations flexibility depending on the level of assurance they need. Their work spans the public, private and third sectors, with reviews tailored to the operational and regulatory challenges of each organisation.
Alongside core internal audit activity, they examine areas such as enterprise risk management, digital governance, fraud prevention and business process improvement. Their portfolio also includes third-party assurance and information governance reviews, allowing organisations to assess both operational controls and wider organisational resilience through a single assurance programme.
Key Highlights
Internal audit outsourcing, co-sourcing and consultancy
Experience across public, private and third sector organisations
Finnovative takes a different approach to audit support, working primarily with UK accountancy firms that need additional capacity for audit engagements. Their services focus on outsourced audit support, helping firms manage routine audit work and documentation while maintaining established workflows. Alongside external audit support, they contribute to internal audit assignments where additional resources are needed for control documentation and audit procedures.
Their team assists with audit working papers, testing and control reviews across a range of non-judgemental audit areas. Internal audit support is available for organisations that need help documenting control design, reviewing control environments and carrying out audit procedures as part of a wider assurance engagement.
Key Highlights
Audit outsourcing support for UK accountancy firms
Assistance with internal and external audit engagements
Support with audit documentation and working papers
Corient Business Solutions support UK accountancy practices with outsourced audit services that fit into existing audit processes and regulatory requirements. Their delivery model is designed for firms that need additional audit capacity without expanding internal teams. Audit work is completed in line with UK financial reporting and audit standards, with support available for both individual assignments and ongoing engagements.
Their audit services cover statutory audit work, financial reporting requirements and assurance activities across different sectors. Practices can choose project-based assistance or broader outsourcing arrangements, depending on workload and client needs. The company also integrates its services with commonly used accounting platforms, making collaboration part of the day-to-day audit process.
Key Highlights
Outsourced audit support for UK accountancy practices
Knowledge of UK audit and financial reporting requirements
Project-based and ongoing engagement options
Support across statutory and financial audits
Integration with major accounting software
Focus on regulatory compliance and audit documentation
Address: The Techno Centre, Puma Way, Coventry, CV1 2TT, United Kingdom
Phone: +44 24 7610 3333
Albion Audit
Albion Audit focuses on outsourced and co-sourced internal audit services for organisations that need an independent audit function or additional support for an existing team. Their approach allows organisations to access internal audit resources without recruiting permanent staff, making it easier to adjust audit capacity as business needs change. Internal audit work is carried out against agreed audit plans and reported directly to audit committees as part of the assurance process.
Their co-sourcing model is designed for organisations that already have an internal audit function but need specialist skills or extra resources for specific assignments. This gives audit teams additional capacity while allowing internal audit activities to continue without disruption and in line with governance requirements.
Address: 279 Chanterlands Avenue, Hull, HU5 4DS, United Kingdom
Phone: +44 7594 738595
Insight Audit Group
Insight Audit Group focuses on outsourced audit support for accountancy firms that need additional audit capacity without expanding their internal teams. Alongside financial and statutory audit work, they carry out internal audit assignments that examine internal controls, operating processes and areas where governance can be strengthened. Their audit support covers the full engagement, from planning through to completion, with flexibility around documentation and audit file preparation.
A significant part of their offering is helping firms manage audit workloads across different types of organisations and regulated sectors. Internal audit reviews are complemented by operational, compliance and forensic audit services, giving firms access to a wider range of assurance work through a single outsourcing partner.
Key Highlights
Audit outsourcing support for accountancy firms
Internal and external audit services
Full audit engagement support
Experience across regulated sectors
Operational, compliance and forensic audit capability
Address: Unit 7, Navigation Business Village Navigation Ways, Ashton-On-Rubble, Preston, Lancashire, PR2 2YP
Phone: 0204-553-9540
Forvis Mazars
Forvis Mazars approach internal audit as part of a wider governance and risk management framework. Their teams support organisations that are building a new internal audit function as well as those looking to outsource or strengthen an existing one. Engagements are planned around business risks, regulatory requirements and organisational priorities, with input from specialists across different industries where required.
Internal audit sits alongside broader consulting and risk advisory services, allowing reviews to cover governance, compliance, technology, operational risk and board responsibilities. Their sector experience spans financial services, public organisations, infrastructure, manufacturing and other regulated industries, giving them a broad perspective on different assurance environments.
Key Highlights
Internal audit outsourcing and advisory
Risk-based audit approach
Governance and compliance reviews
Industry-specific audit expertise
Support for new and existing internal audit functions
Address: 3 Chamberlain Square, Birmingham, B3 3AX, United Kingdom
Phone: +44 (0) 121 232 9500
Crowe
Crowe specialises in internal audit outsourcing for banks and financial services organisations. Their audit teams support firms that need independent assurance across operational, regulatory and technology risks while helping internal audit programmes keep pace with changing industry requirements. Engagements are adapted to each organisation's structure, with a single audit provider covering multiple areas of assurance where needed.
Beyond core internal audit activity, they assess specialist areas including anti-money laundering, consumer compliance, IT controls and lending operations. Their experience is concentrated within financial services, making their audit programmes closely aligned with the governance and regulatory expectations faced by banks and similar organisations.
Address: 3rd Floor, St George's House, 56 Peter Street, Manchester M2 3NQ
Phone: +44 (0)161 214 7500
RSM
RSM delivers internal audit and control services that combine assurance with practical reviews of business processes and governance arrangements. Their approach centres on risk-based audit planning, helping organisations focus assurance work on areas where controls and operational risks have the greatest impact. Reviews cover both the design of controls and how effectively they operate in practice.
Audit findings are supported by recommendations aimed at improving internal processes, reporting and oversight. Their teams also work with boards and audit committees by presenting clear information on control issues, governance and follow-up actions, making internal audit part of wider organisational decision-making.
Key Highlights
Risk-based internal audit planning
Internal control testing
Governance and board reporting support
Operational process reviews
Audit committee support
Performance and control improvement
Services
Internal audit
Internal control reviews
Risk-based audit planning
Control effectiveness testing
Operational audits
Governance reviews
Audit committee support
Board reporting
Contact Information
Website: www.rsmuk.com
LinkedIn: www.linkedin.com/company/rsm-uk
Instagram: www.instagram.com/rsm.uk
Address: 4th Floor, The Capitol, 431 Union Street,Aberdeen, AB11 6DA
Phone: +44 (0)1224 321133
Deloitte
Deloitte offers internal audit outsourcing, co-sourcing and advisory services for organisations looking to strengthen assurance across governance, risk and compliance. Their internal audit teams support both established audit functions and organisations creating new ones, with assignments designed around changing business risks, regulatory expectations and organisational objectives. Their methodology follows recognised professional internal audit standards.
The scope of their internal audit work extends beyond routine assurance reviews to include audit transformation, benchmarking and improvements to existing audit functions. Organisations can use their support on a fully outsourced basis, alongside in-house teams or for specific projects where additional expertise is needed.
Key Highlights
Internal audit outsourcing and co-sourcing
Internal audit advisory
Support aligned with professional audit standards
Audit transformation and benchmarking
Governance and risk assurance
Flexible engagement models
Services
Internal audit outsourcing
Internal audit co-sourcing
Internal audit advisory
Internal audit function design
Audit transformation
Internal audit assessments
Governance reviews
Risk assurance
Contact Information
Website: www.deloitte.com
Facebook: www.facebook.com/deloitteuk
Twitter: x.com/deloitteuk
LinkedIn: www.linkedin.com/company/deloitte
Address: 1 New Street Square, London, EC4A 3HQ, United Kingdom
Phone: +44 (0)20 7936 3000
Protiviti
Protiviti focuses on internal audit outsourcing for organisations that want to combine assurance with technology, risk and operational expertise. Their sourcing models range from fully outsourced internal audit functions to staff augmentation and specialist support for individual projects. Internal audit engagements are built around changing business risks and are supported by specialists in areas such as technology, compliance and operational controls.
Another area of their work is helping organisations modernise internal audit through data-driven techniques, automation and audit transformation. Their teams carry out reviews across technology, fraud risk, regulatory compliance and internal controls while supporting audit committees and management with broader assurance programmes.
Key Highlights
Internal audit outsourcing and strategic sourcing
Audit transformation support
Technology and IT audit expertise
Controls and compliance advisory
Fraud risk management
Data-driven internal audit approaches
Services
Internal audit outsourcing
Technology audits
Audit transformation
Controls advisory
Fraud risk assessments
Regulatory compliance reviews
SOX compliance support
Internal audit staff augmentation
Contact Information
Website: www.protiviti.com
Facebook: www.facebook.com/Protiviti
Twitter: x.com/ProtivitiUK
LinkedIn: www.linkedin.com/company/protiviti-uk-
Instagram: www.instagram.com/protiviti.uk
Address: Second Floor, AIR, 35 Homer Road, Solihull B91 3QJ, United Kingdom
Phone: +44.20.7930.8808
Final Thoughts
Choosing an internal audit outsourcing provider is not only about technical capability. It is equally important to consider whether the provider has experience in your sector, understands your regulatory environment, and can adapt their approach to the size and complexity of your organisation. Some businesses need a fully outsourced internal audit function, while others only require additional support for their existing team or specialist reviews in specific areas.
The providers included in this guide offer different strengths, service models and areas of expertise. Comparing their approach, industry experience and range of internal audit services can help you identify which one is the best fit for your governance, risk management and assurance needs. The aim of this guide is to provide a practical starting point, making it easier to understand the UK market before deciding which provider to speak with.
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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