| A.H. Spares Limited | Wholesale & retail | 1981 |
| A.J. Meechan Ltd. | Professional & scientific | 1995 |
| A.M. Forster Properties Limited | Real estate | 2017 |
| A.S. Audhali (Broiler Farms) Limited | Extraterritorial | 1982 |
| A.S. Audhali Farm Gate Fresh Poultry Limited | Manufacturing | 1981 |
| A2Z Distributor Ltd | Wholesale & retail | 2022 |
| A5 Precision Tooling Ltd | Professional & scientific | 2009 |
| AA & ME Limited | Administrative & support | 2022 |
| AAA Executives Limited | Other services | 2014 |
| AAA GP Services Ltd | Health & social care | 2025 |
| AAH Builders Supplies Limited | Professional & scientific | 1957 |
| AAH Pharmaceuticals Limited | Manufacturing | 1912 |
| Aatos Legal Technology Ltd | Professional & scientific | 2023 |
| AB Hort Limited | Wholesale & retail | 2024 |
| AB K9 Training Limited | Other services | 2023 |
| AB Willows Care Services Ltd | Professional & scientific | 2022 |
| Abbey END Builders Ltd | Construction | 2025 |
| Abbey Grange Boat Lane Residents Management Company Limited | Households | 2025 |
| Abbey House Pharmacy (Daventry) Limited | Wholesale & retail | 2008 |
| Abbey Office Park Ltd | Real estate | 2015 |
| Abbey Park Shelters Limited | Other services | 2020 |
| ABG Management Limited | Professional & scientific | 2024 |
| Abicom International Limited | Information & communication | 2002 |
| ABM Catering (Holdings) Limited | Financial services | 2011 |
| ABM Catering Solutions Limited | Extraterritorial | 2015 |
| ABM Property Investments Limited | Real estate | 2010 |
| Abode Consultancy Ltd | Real estate | 2013 |
| Absolutely Couriers Limited | Extraterritorial | 2016 |
| Abstracta Limited | Information & communication | 2019 |
| ABT Consultants Ltd | Professional & scientific | 2022 |
| AC Electrical & Installation Ltd | Construction | 2026 |
| Academy Plus Group Limited | Information & communication | 2013 |
| Accelerating Talent Limited | Professional & scientific | 2008 |
| Access Engineering Supplies Limited | Wholesale & retail | 2007 |
| Accountancy Advice for YOU Limited | Professional & scientific | 2012 |
| Accounts & Returns (London) Limited | Extraterritorial | 2016 |
| Accounts & Returns Limited | Professional & scientific | 2008 |
| Accurate Video Ltd | Information & communication | 2020 |
| Ace Insight Business Solutions Ltd | Professional & scientific | 2016 |
| Ace Scaffolding Hire Ltd | Construction | 2013 |
| Ace Scaffolding Midlands Ltd | Construction | 2017 |
| Ace the Company Limited | Wholesale & retail | 2023 |
| Acerta Group Limited | Administrative & support | 2016 |
| Aceve UK Ltd | Wholesale & retail | 2021 |
| ACN Consultancy Limited | Professional & scientific | 2020 |
| Acne Limited | Administrative & support | 2008 |
| Acoustics Limited | Professional & scientific | 2001 |
| Acqius Ltd | Professional & scientific | 2023 |
| Acrow UK Ltd | Wholesale & retail | 2005 |
| Action Strategies LLP | | 2004 |
| Action Ventures Limited | Information & communication | 2020 |
| Active Woodlands Limited | Professional & scientific | 2025 |
| Activeu Fitness Solutions Ltd | Health & social care | 2019 |
| Actonia Limited | Professional & scientific | 2021 |
| AD Commerce Ltd | Manufacturing | 2026 |
| AD Fire Limited | Administrative & support | 2012 |
| AD Tours of Egypt Limited | Administrative & support | 2012 |
| Adam Greenwood Design Ltd | Other services | 2025 |
| Adaptos Limited | Professional & scientific | 1993 |
| Adastec UK Limited | Information & communication | 2025 |
| Adat Technologies Limited | Professional & scientific | 2013 |
| Addington Development Company Limited | Administrative & support | 2017 |
| Additae Valorem Limited | Other services | 2015 |
| ADE Engineering Limited | Professional & scientific | 2024 |
| Adelon Capital, LP | | 2020 |
| Adgero UK Limited | Transport & logistics | 2017 |
| Adloox Limited | Professional & scientific | 2013 |
| ADM Business Limited | Real estate | 2023 |
| Admenta Pension Trustees Limited | Professional & scientific | 1980 |
| Admenta UK Limited | Professional & scientific | 1995 |
| Adore the Floor Ltd | Wholesale & retail | 2021 |
| Adr-Class Ltd | Transport & logistics | 2026 |
| Adsoft Consulting Ltd | Information & communication | 2024 |
| Advance Fumigation and Pest Control Limited | Agriculture & fishing | 1992 |
| Advance to Go Limited | Professional & scientific | 2015 |
| Advanced Design & Development Limited | Professional & scientific | 1992 |
| Advanced Fertility and Gynaecology Care Ltd | Health & social care | 2013 |
| Advanced Field Solutions UK Limited | Administrative & support | 2010 |
| Advanced Handling Limited | Manufacturing | 2011 |
| Advanced Therapeutics (UK) Limited | Wholesale & retail | 2005 |
| Advanced Vehicle Contracts Limited | Administrative & support | 2000 |
| Advantage Global Trade Exports Limited | Extraterritorial | 2012 |
| Advantage Global Trade Solutions Limited | Financial services | 2011 |
| Advena Limited | Health & social care | 1998 |
| Adventure Sports (Warwickshire) Limited | Arts & recreation | 1987 |
| Adventures Inn Limited | Hospitality | 2006 |
| Adzp Ltd | Construction | 2024 |
| AEB (International) Limited | Information & communication | 2000 |
| AEC Software Ltd | Wholesale & retail | 2020 |
| Aeds Consultants Limited | Professional & scientific | 2004 |
| AEM Associates Limited | Professional & scientific | 1997 |
| Aeros Atpl Limited | Education | 2017 |
| Aeros Aviation Group Limited | Professional & scientific | 2006 |
| Aeros Global Limited | Transport & logistics | 2000 |
| Aeros Leasing Limited | Transport & logistics | 2006 |
| Aeros Limited | Transport & logistics | 2002 |
| Aeros Maintenance Limited | Manufacturing | 1997 |
| AF Offshore Decom UK Ltd | Construction | 2008 |
| AFE Digital Ltd | Professional & scientific | 2025 |
| Aftermarketuk Ltd | Wholesale & retail | 2021 |