| Ace Payroll Services Ltd | Professional & scientific | 2022 |
| Ace Preferred Ltd | Professional & scientific | 2015 |
| Ace Realtor Ltd | Real estate | 2019 |
| Ace Vehicle Solutions Ltd | Administrative & support | 2025 |
| Aceso Healthcare Limited | Wholesale & retail | 2014 |
| ACJ Creative Limited | Professional & scientific | 2025 |
| ACM Tuina Ltd | Other services | 2021 |
| ACN Plumbing & Heating Ltd | Energy | 2012 |
| Acorn Direct Limited | Administrative & support | 2022 |
| ACP1 Ltd | Financial services | 2020 |
| Acquire Performance Marketing Limited | Professional & scientific | 2014 |
| Acre Invest (Luton) Limited | Construction | 2016 |
| Acre Invest (ST Albans) Limited | Construction | 2016 |
| Acrelon Limited | Construction | 1978 |
| ACS Synergy Limited | Professional & scientific | 2024 |
| Active Body Osteopathy Limited | Other services | 2024 |
| Active Resilience Limited | Arts & recreation | 2026 |
| Active Training Organisation Limited | Wholesale & retail | 2004 |
| Activecare Online Limited | Wholesale & retail | 2019 |
| Actura Ltd | Professional & scientific | 2022 |
| Actus Software Ltd | Professional & scientific | 2016 |
| Aculytics Ltd | Information & communication | 2022 |
| Acupuncture 1ST Limited | Health & social care | 2015 |
| AD Hazell Limited | Other services | 2014 |
| Adahsa Limited | Health & social care | 2014 |
| Adam Eastman Management Ltd | Construction | 2010 |
| Adams Independent Assessors Limited | Administrative & support | 2010 |
| Adarama Limited | Information & communication | 2021 |
| Addana Property Limited | Construction | 2017 |
| Addis Consulting Limited | Professional & scientific | 2010 |
| Addis Fine Art Limited | Wholesale & retail | 2014 |
| Adebanke Tade Limited | Professional & scientific | 2014 |
| Adelaide Stewart Limited | Construction | 2014 |
| Adelphi Property Investments Ltd | Real estate | 2024 |
| Adeo Secondary SPV LLP | | 2021 |
| Adept Automation Ltd | Manufacturing | 2021 |
| Adesa Ltd | Professional & scientific | 2026 |
| Adhab Ltd | Wholesale & retail | 2024 |
| Aditus Limited | Professional & scientific | 1999 |
| ADL Electrical Services Ltd | Construction | 2020 |
| Adleigh Building Services Ltd | Construction | 2005 |
| ADMIN2DAY Ltd | Administrative & support | 2020 |
| Admiral (UK) Contracting Limited | Construction | 2005 |
| Admo Financials Limited | Professional & scientific | 2012 |
| Adooa Limited | Information & communication | 2014 |
| Adrian J Wright Consulting Ltd | Professional & scientific | 2015 |
| ADS Medi Care Ltd | Wholesale & retail | 2014 |
| Advance Change Ltd | Professional & scientific | 2008 |
| Advance Edtech Limited | Education | 2017 |
| Advance Group Holdco Limited | Manufacturing | 2024 |
| Advance Innovation Limited | Manufacturing | 2006 |
| Advanced Drainage Solutions Limited | Construction | 2006 |
| Advanced Oral Implants Limited | Health & social care | 2010 |
| Advantage Itech Ltd | Construction | 2022 |
| Advaya IT Consultants Ltd | Information & communication | 2023 |
| Adway AI Limited | Information & communication | 2021 |
| Aegir Crest Limited | Real estate | 1999 |
| Aegis Advisory Services Ltd | Professional & scientific | 2025 |
| AEM24 Ltd | Real estate | 2024 |
| Aequitas Consulting Limited | Administrative & support | 2009 |
| Aero Consulting Ltd | Professional & scientific | 2024 |
| Aerorama Ltd | Manufacturing | 2024 |
| Aerosmart Training Ltd | Transport & logistics | 2021 |
| Aesthatony Limited | Health & social care | 2018 |
| Aesthetics by Aina Ltd | Other services | 2022 |
| Aesthetics by Ireland Ltd | Health & social care | 2026 |
| AF Strategic Marketing Solutions Limited | Professional & scientific | 2026 |
| Afih Limited | Real estate | 2023 |
| Afih Services Limited | Professional & scientific | 2025 |
| AFK Group Holdings Ltd | Financial services | 2026 |
| African Art Contemporary Ecosystems | Arts & recreation | 2016 |
| Afrikey ENT Ltd | Arts & recreation | 2019 |
| Afrin Investment Ltd | Real estate | 2023 |
| AFS67 Ltd | Wholesale & retail | 2025 |
| Afternoonify Ltd | Information & communication | 2015 |
| AG 147 Limited | Real estate | 2025 |
| AG Consultancy & Facade Management Limited | Construction | 2018 |
| AG Roofing Services Ltd | Construction | 2025 |
| Agard Forever Limited | Wholesale & retail | 2023 |
| Agaur Ltd | Wholesale & retail | 2001 |
| Agelis Peltier Properties Ltd | Real estate | 2023 |
| Agentic A.I. Consulting Limited | Information & communication | 2025 |
| Agentic First Limited | Professional & scientific | 2025 |
| Agentic Impact Limited | Professional & scientific | 2025 |
| Agentic Value Limited | Professional & scientific | 2025 |
| Agile Architecture Consulting Ltd | Information & communication | 2022 |
| Agile Data Warehouse Solutions Ltd | Information & communication | 2013 |
| Agile Governance Ltd | Information & communication | 2023 |
| Agile Innovation Limited | Information & communication | 2023 |
| AGM Centre Limited | Education | 2021 |
| Agoura Limited | Professional & scientific | 2013 |
| Agrippa Digital Ltd | Information & communication | 2026 |
| Agritrade News Limited | Information & communication | 2014 |
| AGW Plumbing & Heating Limited | Construction | 2015 |
| AGX Combat and Performance Ltd | Education | 2026 |
| AH Evolve Limited | Professional & scientific | 2024 |
| Ahbab ALI Ltd | Professional & scientific | 2019 |
| Ahead Mediation and Consulting Ltd | Administrative & support | 2026 |
| Aheadstyle Ltd | Other services | 2023 |
| Ahmed Akhtar Properties Limited | Real estate | 2018 |