| Anthony Bates Limited | Professional & scientific | 2013 |
| Anthony Mark Kitchens Ltd | Manufacturing | 2024 |
| Anthony Seymour & Co Ltd | Professional & scientific | 2006 |
| Anthony Wells Associates Limited | Professional & scientific | 2020 |
| Antiars Limited | Real estate | 2004 |
| Antonious’S Estate Online Ltd | Real estate | 2024 |
| ANU Property Limited | Real estate | 2021 |
| Anvc Ltd | Real estate | 2016 |
| Anydata Holding Company Ltd | Information & communication | 2026 |
| Anydata Solutions Ltd | Information & communication | 2013 |
| AP Aircraft Maintenance Ltd | Professional & scientific | 2025 |
| Aperture Watch Limited | Wholesale & retail | 2025 |
| Apex Auctions Limited | Wholesale & retail | 2002 |
| Apex Chiropractic Limited | Health & social care | 2017 |
| Apex Decorators Hove Limited | Construction | 2010 |
| Apex EVO Ltd | Other services | 2023 |
| Apex Festival Services Ltd | Hospitality | 2020 |
| Apex Group Corporate Services Ltd | Professional & scientific | 2019 |
| Apex Roofing & General Building Ltd | Construction | 2024 |
| Apex Structural Design Limited | Professional & scientific | 2023 |
| Apex Supercar Club Limited | Other services | 2020 |
| Apexcaterer Ltd | Hospitality | 2019 |
| Apiaka Holdings Ltd | Financial services | 2026 |
| APM Contractors Ltd | Construction | 2011 |
| Apollo Tanning & Beauty Ltd | Other services | 2012 |
| Apoyar Limited | Information & communication | 2001 |
| Appcelerate LLP | | 2008 |
| Applicando Ltd. | Information & communication | 2023 |
| Applyshare Property Management Limited | Households | 1994 |
| Appnexus Ltd | Information & communication | 2024 |
| Appoid Ltd | Information & communication | 2026 |
| Appozo Ltd | Information & communication | 2015 |
| Approved Builders Group Limited | Professional & scientific | 2022 |
| Apptech Solutions Ltd | Information & communication | 2014 |
| April 11 Limited | Wholesale & retail | 2025 |
| APS Aegis (UK) Ltd | Construction | 2026 |
| APS Aegis Limited | Construction | 2007 |
| Apterro Ltd | Information & communication | 2025 |
| APX Solutions Limited | Construction | 2022 |
| AQ Brighton Ltd | Real estate | 2021 |
| AQ Willesden Limited | Real estate | 2021 |
| Aqua Fluency Ltd | Information & communication | 2015 |
| Aqua Moon Creative Ltd | Professional & scientific | 2021 |
| Aqua Safari UK Limited | Hospitality | 2019 |
| Aquakiddies/Babies in Essex Limited | Education | 2010 |
| Aquanaut Consulting Ltd | Professional & scientific | 2021 |
| Aquarius Test Engineering Ltd | Professional & scientific | 2024 |
| Aquatron Limited | Construction | 1996 |
| AR Fitness Solutions Ltd | Other services | 2013 |
| AR Freehold Ltd | Households | 2025 |
| Araminta Hall Limited | Information & communication | 2017 |
| Arar's Minimarket Ltd | Wholesale & retail | 2019 |
| Arash Sahoori Ltd | Hospitality | 2024 |
| Arbeyu Ltd | Hospitality | 2022 |
| Arbor Eatum Ltd | Hospitality | 2025 |
| Arbor Wood Floors Ltd | Construction | 2007 |
| ARC Organisation LLP | | 2008 |
| ARC Training Services Ltd | Administrative & support | 2015 |
| Arcadia Cigars Eastbourne Limited | Wholesale & retail | 2024 |
| Arcadia Cigars Gatwick Airport Limited | Wholesale & retail | 2025 |
| Arcadia Cigars Group Limited | Wholesale & retail | 2023 |
| Arcadia Cigars Heathrow T5 Limited | Wholesale & retail | 2025 |
| Arcadia Cigars Kensington Limited | Extraterritorial | 2023 |
| Arcadia Cigars Limited | Wholesale & retail | 2024 |
| Arcane Atlas Games LLP | | 2021 |
| Arch Michael Limited | Extraterritorial | 2015 |
| Archibald Butler Limited | Information & communication | 2012 |
| Archie's Brighton Ltd | Wholesale & retail | 2022 |
| Archipelagos Gyros Ltd | Hospitality | 2020 |
| Arco Hotels Limited | Hospitality | 2013 |
| Arco Telecoms Limited | Information & communication | 2016 |
| Ardea London Limited | Manufacturing | 2025 |
| Area Developments Limited | Construction | 2013 |
| Area Investments Limited | Real estate | 2016 |
| Area Residential Limited | Real estate | 2013 |
| Areley House Care Ltd | Health & social care | 2017 |
| Arena International Strategy Ltd | Financial services | 2018 |
| Aresidence Limited | Hospitality | 2025 |
| Arete Homelets Limited | Extraterritorial | 2011 |
| Argentum Project Management Ltd | Professional & scientific | 2025 |
| Argofy Limited | Professional & scientific | 2025 |
| Aria Auto and Tyre Ltd | Wholesale & retail | 2025 |
| Arialia Limited | Health & social care | 2025 |
| ARK Artists Ltd | Administrative & support | 2014 |
| ARK Investments Brighton Limited | Real estate | 2025 |
| Arkitex Design Limited | Information & communication | 2010 |
| Arktick Ltd | Wholesale & retail | 2026 |
| Arlow House Hove Limited | Households | 1999 |
| Armadillo Translation Limited | Other services | 2014 |
| Arman Cab's Ltd | Transport & logistics | 2025 |
| ARO Legal Ltd | Professional & scientific | 2020 |
| Aroa Property Developments Limited | Real estate | 2005 |
| Aroco Limited | Information & communication | 2020 |
| Aron Cleaning Ltd | Administrative & support | 2025 |
| Arpena Limited | Hospitality | 2019 |
| Arrow and Bull Ltd | Health & social care | 2016 |
| Arrow Factory UK Ltd | Hospitality | 2022 |
| Arseen & Raya Limited | Hospitality | 2021 |
| Art Consensus Limited | Arts & recreation | 2010 |
| Art Fair Services UK Ltd | Administrative & support | 2020 |