| Angie Delivery Services Ltd | Transport & logistics | 2023 |
| ANH Leisure Ltd | Arts & recreation | 2023 |
| ANIM8 Productions Limited | Information & communication | 2013 |
| Anjt Properties Limited | Real estate | 2024 |
| Ankr Property Investments Ltd | Real estate | 2025 |
| Annabel Sweet Limited | Administrative & support | 2016 |
| Annami Property Limited | Real estate | 2016 |
| ANS Elite Properties Ltd | Real estate | 2022 |
| Ans-Greenways Limited | Real estate | 2024 |
| Anshh Property Ventures Limited | Real estate | 2023 |
| Anson Road Limited | Households | 1990 |
| Ansvenus Limited | Real estate | 2024 |
| Anthemion Limited | Wholesale & retail | 2002 |
| Anthony J Hulse Limited | Professional & scientific | 2010 |
| Anto Cladding Ltd | Construction | 2013 |
| Anton Lines Services Limited | Administrative & support | 2010 |
| AOX Logistics Ltd. | Transport & logistics | 2016 |
| APB Resin Refinishing Limited | Construction | 2026 |
| Apex Branch Media Ltd | Professional & scientific | 2024 |
| Appian Advisory Limited | Professional & scientific | 2026 |
| Apptelic Ltd | Information & communication | 2011 |
| April Banbury Bridal Ltd | Professional & scientific | 2025 |
| Aprite (GB) Limited | Wholesale & retail | 1996 |
| Aproov Ltd | Information & communication | 2024 |
| APS Fitness Limited | Arts & recreation | 2011 |
| Aquam Liberum Ltd | Manufacturing | 2025 |
| Aquashine Auto Spa Ltd | Administrative & support | 2025 |
| Aquity Limited | Real estate | 2018 |
| Aqumen Consulting Limited | Professional & scientific | 2018 |
| AR Patel Properties Ltd | Real estate | 2025 |
| AR Prime Ltd | Wholesale & retail | 2024 |
| AR UK Solutions Limited | Information & communication | 2026 |
| AR19 Ltd | Professional & scientific | 2024 |
| Araaya Properties Limited | Real estate | 2022 |
| Aras Property Services Ltd | Real estate | 2021 |
| Aravali Properties Ltd | Real estate | 2019 |
| Arbol Euro Consulting Ltd | Other services | 2012 |
| Arborem Limited | Administrative & support | 2007 |
| ARC Electrics Ltd | Energy | 2023 |
| ARC Insights Ltd | Information & communication | 2008 |
| Arcadia Desiccant Technology Limited | Manufacturing | 2021 |
| Arcaz Ltd | Professional & scientific | 2016 |
| Archangel Capital Partners LLP | | 2026 |
| Archbold Residence Limited | Real estate | 2025 |
| Archer Rusby Solicitors Ltd | Professional & scientific | 2011 |
| Architectural Brickwork Services Limited | Construction | 2025 |
| Architectural Design + Build Limited | Construction | 2020 |
| Archmen Ltd | Wholesale & retail | 2021 |
| Archplan Designs Limited | Professional & scientific | 2004 |
| Arck Dental Care Limited | Health & social care | 2010 |
| Arcl Investments Ltd | Real estate | 2021 |
| Ardmore New Projects Limited | Financial services | 2025 |
| Areaview Limited | Construction | 1996 |
| Arem Consulting Limited | Professional & scientific | 2013 |
| Arghya Enterprises Ltd | Wholesale & retail | 2008 |
| Argyle Ealing Limited | Construction | 2015 |
| Arka Mahaganapathy | Health & social care | 2007 |
| Arkley Accounting Solutions Ltd | Professional & scientific | 2018 |
| Arkley Care Services Ltd | Health & social care | 2015 |
| Arklow Court Management Company Limited | Households | 1999 |
| Arky Limited | Information & communication | 2016 |
| Arnold Homes (UK) Limited | Wholesale & retail | 2001 |
| Arnold Homes Chalfont Limited | Construction | 2019 |
| Arosco Golf Promotions Ltd | Other services | 2025 |
| Arpx Ltd | Information & communication | 2025 |
| Arrowroot Limited | Professional & scientific | 2008 |
| Art Time Barber Ltd | Other services | 2021 |
| Art Wood DE Corfu Limited | Manufacturing | 2021 |
| Arte Sano Limited | Professional & scientific | 2019 |
| Arthav Venture Ltd | Real estate | 2025 |
| Artificial Intelligence Pioneers Ltd | Administrative & support | 2024 |
| Artis Architects Limited | Professional & scientific | 2012 |
| Artworld Agency Limited | Other services | 2018 |
| Arunagiri UK Ltd | Wholesale & retail | 2007 |
| Arven Capital Holdings Limited | Financial services | 2019 |
| ARW Consulting Ltd | Professional & scientific | 2016 |
| ARW Energy Consulting Ltd | Professional & scientific | 2026 |
| Arwa Properties Ltd | Real estate | 2021 |
| Arya Restaurant Limited | Hospitality | 2025 |
| As&Aa Plumbing Limited | Construction | 2021 |
| Asap Repairs Limited | Wholesale & retail | 2020 |
| Ascendancy Digital Limited | Professional & scientific | 2018 |
| Asgard House Limited | Professional & scientific | 2002 |
| Ashby Business Consulting Limited | Information & communication | 2010 |
| Ashcroft IT Design Limited | Information & communication | 2014 |
| Ashiana Partnership LLP | | 2021 |
| Ashiana Real Estate Ltd | Real estate | 2022 |
| Ashley Medical Communications Limited | Professional & scientific | 2000 |
| Ashon Limited | Professional & scientific | 2008 |
| Ashridge Associates Limited | Professional & scientific | 2013 |
| Ashurst Property Developments Limited | Real estate | 2020 |
| Asid Tech PVT Ltd | Information & communication | 2020 |
| ASJ Living Ltd | Real estate | 2024 |
| Askal Consulting Ltd | Other services | 2021 |
| Aspiring Capital Partners Ltd | Professional & scientific | 2023 |
| Asrg Limited | Other services | 2021 |
| Asset Finance Policy Limited | Professional & scientific | 2014 |
| Assisted Solutions Limited | Information & communication | 2024 |
| Associate Consulting Ltd | Professional & scientific | 2003 |
| Assured Projects Limited | Construction | 2007 |