| Atelier Ellis Architecture Ltd | Professional & scientific | 2016 |
| Atelier Niche Limited | Wholesale & retail | 2025 |
| Atelier Steel Limited | Manufacturing | 2025 |
| ATG Auto Tuning Ltd | Wholesale & retail | 2016 |
| Atgtbt Property Ltd | Professional & scientific | 2019 |
| Athena Gardens Sussex Ltd | Administrative & support | 2025 |
| Athena Promotions Ltd | Information & communication | 2025 |
| Athletic-Iq Limited | Information & communication | 2020 |
| Athlome Limited | Professional & scientific | 2016 |
| Atkins GAS Services Limited | Construction | 2011 |
| Atlas Food and Transportation Limited | Professional & scientific | 2021 |
| Atlas Rise Chiropractic Ltd. | Health & social care | 2024 |
| Atom Business Consultants Ltd | Professional & scientific | 2024 |
| Atom Metalwork Ltd | Administrative & support | 2019 |
| Atomic Clouds Ltd | Information & communication | 2016 |
| Atomise Entertainment LLP | | 2017 |
| ATP Performance Ltd | Administrative & support | 2022 |
| ATR Auto Services Limited | Other services | 2017 |
| Attollo Health Ltd | Wholesale & retail | 2009 |
| Auction House Services Limited | Administrative & support | 2000 |
| Audio Description Services Ltd | Arts & recreation | 2024 |
| Audio Visual Services Ltd | Manufacturing | 2017 |
| AUK Consulting Limited | Administrative & support | 2006 |
| Aumeed&Co Limited | Real estate | 2023 |
| Aumeeddental&Co Limited | Health & social care | 2026 |
| Aurea Holidays Group Limited | Hospitality | 2024 |
| Aurora Digital Ventures Limited | Professional & scientific | 2024 |
| Ausome Caravans Limited | Administrative & support | 2026 |
| Austen Phillips Ltd | Construction | 2001 |
| Austins Cradles (Eastbourne) Limited | Construction | 1982 |
| Austins Holding Limited | Financial services | 2019 |
| Authentic Media Productions Ltd | Information & communication | 2010 |
| Auto Acquisitions Limited | Wholesale & retail | 2026 |
| Auto Bench Limited | Wholesale & retail | 2010 |
| Auto Foxx Limited | Wholesale & retail | 2023 |
| Auto-Bodycare Service Centre Limited | Wholesale & retail | 2003 |
| Autograph Dental Limited | Health & social care | 2022 |
| Autograph IT NOW Limited | Wholesale & retail | 2017 |
| AV8 Records Limited | Administrative & support | 2016 |
| Ava-Tia Limited | Other services | 2019 |
| Avanisa Limited | Other services | 2025 |
| Avebury Management (Langney) Limited | Households | 2020 |
| Avelon Network Ltd | Information & communication | 2021 |
| Avenor Solutions Limited | Professional & scientific | 2025 |
| Aventen Innovations Ltd | Wholesale & retail | 2022 |
| Avenue Employment Limited | Financial services | 2021 |
| Avenue Mansions Management RTM Company Limited | Households | 2009 |
| Avgp Ltd | Real estate | 2010 |
| Aviac Partners Limited | Real estate | 2026 |
| Aviacom Project Management Limited | Manufacturing | 2021 |
| Avinny Limited | Administrative & support | 2008 |
| Avon Mappi Group Ltd | Financial services | 2025 |
| Avon Mappi Ltd | Professional & scientific | 2025 |
| Avonmore Management Company(Eastbourne)Limited | Households | 1970 |
| Avron London Ltd | Manufacturing | 2021 |
| AW & X Ltd | Education | 2025 |
| AW Strategic Limited | Professional & scientific | 2023 |
| Awaremind Consultancy Ltd | Administrative & support | 2020 |
| Awssome Property Limited | Real estate | 2025 |
| Axecc Ltd | Health & social care | 2024 |
| Axer Limited | Professional & scientific | 2013 |
| Axieos Ltd | Professional & scientific | 2023 |
| Axisops Limited | Information & communication | 2013 |
| Axzam Consulting Limited | Professional & scientific | 2021 |
| Ayesha Estates Limited | Real estate | 2024 |
| Ayeyarwady Ltd | Hospitality | 2023 |
| Ayka Ltd | Wholesale & retail | 2023 |
| AYM Studio Ltd | Extraterritorial | 2018 |
| Aymat Consulting Ltd | Health & social care | 2023 |
| Aymond Grange Properties Limited | Real estate | 1998 |
| Ayosk Limited | Information & communication | 2019 |
| Ayrshire Dental Limited | Health & social care | 2024 |
| Azpropholdings Ltd | Real estate | 2025 |
| Azur Services Ltd | Wholesale & retail | 2025 |
| Azura SMG Ltd | Health & social care | 2019 |
| B Arslan Limited | Real estate | 2026 |
| B C Reinstating Ltd | Construction | 2020 |
| B C Surfacing Ltd | Construction | 2025 |
| B G Tarrant Ltd | Financial services | 2021 |
| B M Divis Group Limited | Financial services | 2023 |
| B M Divis Investments Limited | Real estate | 2023 |
| B M Divis Limited | Hospitality | 2022 |
| B Wilkinson Pest Control Ltd | Administrative & support | 2026 |
| B Y Retirement Property Ltd | Real estate | 2023 |
| B&B Real Assets Limited | Real estate | 2022 |
| B&C Pain Management Limited | Health & social care | 2018 |
| B&S Scaffolding Limited | Construction | 2015 |
| B.C.S.S. Car Sounds Limited | Wholesale & retail | 2005 |
| B.D.F. Commercial Ltd | Manufacturing | 2012 |
| B.E.M. Builders & Decorators Limited | Construction | 2001 |
| B.G.E Invest Ltd | Real estate | 2026 |
| B.G.E Properties Ltd | Real estate | 2023 |
| B.G.W. Limited | Real estate | 1988 |
| B.M. Hepburn Limited | Construction | 1978 |
| B.T. (Land and Development) Limited | Administrative & support | 2007 |
| B3TECH Limited | Professional & scientific | 2025 |
| BA Installations Limited | Construction | 2023 |
| Ba&Lu Ltd | Hospitality | 2023 |
| BAA & Barrel Limited | Hospitality | 2025 |
| Baba IT Services Limited | Professional & scientific | 2019 |