| Assensus Ltd | Other services | 2014 |
| Asset Concierge Ltd | Real estate | 2025 |
| Asset Protect Solutions Ltd | Administrative & support | 2016 |
| Assigned Limited | Professional & scientific | 2014 |
| Assist Care Agency Limited | Health & social care | 2003 |
| Associate Films Limited | Information & communication | 2014 |
| Association of Managing Agents CIC | Professional & scientific | 2024 |
| Association of Property Buyers (National) Limited | Other services | 2014 |
| Assured Home Improvement Solutions Limited | Construction | 2026 |
| Aston Executive Consulting Ltd | Administrative & support | 2019 |
| Astra Demolition Limited | Construction | 2004 |
| Astracolour Photographic Services Limited | Professional & scientific | 2020 |
| Astric Medical Limited | Manufacturing | 2010 |
| Astro Kobi Limited | Information & communication | 2026 |
| Astrox Properties Ltd | Real estate | 2025 |
| At-Taqwa Nest UK Limited | Transport & logistics | 2025 |
| ATB Boxall Limited | Construction | 2024 |
| ATC Fashions (Sussex) Limited | Information & communication | 2018 |
| ATC Fire Alarms Ltd | Administrative & support | 2016 |
| Atelier Petworth Limited | Wholesale & retail | 2016 |
| Ather Medicals Limited | Administrative & support | 2010 |
| Atherton's Construction Ltd | Construction | 2013 |
| Atlantic IVD Ltd | Professional & scientific | 2023 |
| Atlas Global Commodities Ltd | Administrative & support | 2015 |
| Atlas Scaffolding (UK) Ltd | Construction | 2007 |
| Atlas Trade Finance Limited | Financial services | 1997 |
| Atlas UK Properties Ltd | Real estate | 2017 |
| Atmospheric Zone Limited | Wholesale & retail | 2002 |
| Atom Promotions Ltd | Arts & recreation | 2015 |
| Atonal Music Agency Ltd | Administrative & support | 2018 |
| Attain Limited | Information & communication | 2004 |
| Attentive Records Limited | Information & communication | 2011 |
| ATV Media Ltd | Information & communication | 2022 |
| Aude Sapere Pharma Services Limited | Information & communication | 2026 |
| Audience Growers Limited | Information & communication | 2022 |
| Augustus Brandt Antiques International Limited | Administrative & support | 2008 |
| Aura Property Ventures Ltd | Construction | 2023 |
| Aura Vardis Leasehold Ltd | Real estate | 2025 |
| Aura Vardis Ltd | Real estate | 2025 |
| Auralight Living Ltd | Construction | 2024 |
| Auramarket Accessories Ltd | Wholesale & retail | 2025 |
| Aurea Fides Limited | Wholesale & retail | 2024 |
| Aurea Properties Ltd | Real estate | 2024 |
| Aurelia Hive Ltd | Wholesale & retail | 2026 |
| Aurex Power Solutions Ltd | Construction | 2026 |
| Aurora Building Group Ltd | Construction | 2023 |
| Austen Smith Limited | Real estate | 2012 |
| Austens Apartments Ltd | Hospitality | 2017 |
| Authentic Taekwon-Do Association CIC | Arts & recreation | 2022 |
| Authoring House Limited | Administrative & support | 2009 |
| Auto Cosmetix Limited | Wholesale & retail | 2001 |
| Auto Empire Garages Limited | Wholesale & retail | 2020 |
| Autochek Holdings Limited | Financial services | 2022 |
| Automarine Diesel Services Limited | Wholesale & retail | 2012 |
| Automation Design Systems Limited | Professional & scientific | 2003 |
| Automatrope Ltd | Information & communication | 2020 |
| Automotive Body Consultancy Limited | Professional & scientific | 1989 |
| Autopaints (Brighton) Limited | Wholesale & retail | 2003 |
| Auzar Surgical Ltd | Manufacturing | 2023 |
| AV Care Consultancy Ltd | Professional & scientific | 2025 |
| AV Plastering and Damp Limited | Construction | 2023 |
| AV1 Tiling & Bathrooms Limited | Construction | 2019 |
| AV8 (GB) Limited | Information & communication | 2010 |
| AVA Electrical Ltd | Construction | 2010 |
| AVA of Norway UK Ltd | Wholesale & retail | 2022 |
| AVA Services Group Limited | Professional & scientific | 2019 |
| Avanti Consult Limited | Professional & scientific | 2024 |
| Avereco (Basingstoke) Limited | Real estate | 2008 |
| Avereco Limited | Real estate | 2010 |
| Avery Design and Engineering Ltd | Professional & scientific | 2022 |
| Avesar Group Ltd | Wholesale & retail | 2025 |
| Aviation Claims Limited | Administrative & support | 2021 |
| Avolon Sun Ltd | Professional & scientific | 2021 |
| Avon Sussex Limited | Real estate | 1997 |
| Avonstour Limited | Professional & scientific | 2017 |
| AW Holman Property Limited | Real estate | 2026 |
| AXE Investments Ltd | Real estate | 2021 |
| Axelsonics Ltd | Information & communication | 2024 |
| Axios Finance Ltd | Financial services | 2026 |
| Axtell Food Safety Limited | Professional & scientific | 2023 |
| Aylina Limited | Hospitality | 2023 |
| Ayres Bright Vickers Limited | Professional & scientific | 2002 |
| Ayres Driveways Limited | Construction | 2019 |
| Azucu Limited | Extraterritorial | 2009 |
| Azuvu Limited | Extraterritorial | 2012 |
| B & B Electrical Installations Limited | Wholesale & retail | 1977 |
| B & K Construction (South) Ltd | Construction | 2018 |
| B Bell Plastering Ltd | Construction | 2024 |
| B F J Engraving Limited | Administrative & support | 2002 |
| B G Groundworks Ltd | Construction | 2026 |
| B LUX Nails Ltd | Other services | 2024 |
| B M Builders (Southern) Ltd | Construction | 2006 |
| B Rock 1 Ltd | Hospitality | 2025 |
| B Rock 2 Ltd | Hospitality | 2025 |
| B Smart Interiors Limited | Construction | 2021 |
| B Ventures Limited | Real estate | 2025 |
| B W Kitchens Limited | Construction | 2019 |
| B Yourself Properties & Investments Ltd | Real estate | 2017 |
| B&B Beauty Limited | Other services | 2026 |
| B&O Martial Arts Ltd | Other services | 2022 |