| Apex Corporate Center Ltd | Real estate | 2023 |
| Apex Data Cabling Limited | Information & communication | 2009 |
| Apex LUX Ltd | Wholesale & retail | 2026 |
| Apex Music Group Limited | Information & communication | 2026 |
| Apex Technologies Ltd | Information & communication | 2021 |
| Apollo Technology (UK) Ltd | Wholesale & retail | 2025 |
| Appeer Community Interest Company | Information & communication | 2019 |
| Appexx Global Ltd | Information & communication | 2024 |
| Applabs Odt+Adt Ltd | Information & communication | 2024 |
| Apple & Clover Ltd | Manufacturing | 2019 |
| Apple Seed Consulting Ltd | Administrative & support | 2021 |
| Appletree Holdings Limited | Financial services | 1986 |
| Applied Communications Inc. U.K. Holding Limited | Professional & scientific | 1993 |
| Applied Ingenuity Limited | Professional & scientific | 2001 |
| Approachways Projects Limited | Construction | 2025 |
| Approoved Ltd | Administrative & support | 2025 |
| Appsxchange Limited | Transport & logistics | 2001 |
| APS Catering Limited | Hospitality | 2025 |
| AQK Ventures Ltd | Wholesale & retail | 2024 |
| Aqua Capital SCP Limited | Construction | 2022 |
| Aqua Communications Limited | Other services | 2009 |
| Aqua Core Services Ltd | Construction | 2026 |
| Aqua-Flow Environmental Ltd. | Water & waste | 2023 |
| Aquastone Pool Finishes STS Ltd | Construction | 2020 |
| AR Express Impex Ltd | Transport & logistics | 2023 |
| AR Fine Dinners Ltd | Hospitality | 2020 |
| AR Friends Limited | Extraterritorial | 2023 |
| Arabidopsis Events UK Limited | Administrative & support | 2018 |
| Araceli's Kitchen Ltd | Hospitality | 2025 |
| Aragon Place (Brookwood) Management Company Limited | Households | 2004 |
| ARC & Co Private Finance Ltd | Financial services | 2009 |
| ARC8 Projects Limited | Professional & scientific | 2007 |
| Arcadian Marketing Ltd | Administrative & support | 2019 |
| Arcas Property Ltd | Real estate | 2025 |
| Archai Diagnostics Limited | Health & social care | 2024 |
| Archai Technology Limited | Health & social care | 2024 |
| Architecting Technology Ltd | Information & communication | 2014 |
| Archway Software Design Ltd | Information & communication | 2025 |
| Areawise Limited | Real estate | 1977 |
| Ares Sneakers Ltd | Manufacturing | 2024 |
| Argent Property Management Limited | Real estate | 2023 |
| Aria MGT Ltd | Households | 2026 |
| Aria Technologies Limited | Information & communication | 2018 |
| Arian Chauffeurs Limited | Transport & logistics | 2026 |
| Ariatech Limited | Information & communication | 2012 |
| ARK Scenic Ltd | Information & communication | 2025 |
| Arke Optics Ltd | Arts & recreation | 2023 |
| Arkfin Limited | Financial services | 2012 |
| Arkmore Limited | Professional & scientific | 2004 |
| ARM Secretaries Limited | Administrative & support | 1991 |
| ARM4G3DON Productions Ltd | Information & communication | 2026 |
| Arma Cine Ltd | Arts & recreation | 2023 |
| Armana Systems Limited | Information & communication | 2014 |
| Armani Food & Beverage Limited | Hospitality | 2023 |
| Armani Retailers Limited | Wholesale & retail | 2022 |
| Armybits Limited | Manufacturing | 2020 |
| Arnold Holdco Ltd | Professional & scientific | 2024 |
| Aroma Class Limited | Hospitality | 2026 |
| Arora Build & Development Ltd | Construction | 2026 |
| Arpina Ltd | Real estate | 2021 |
| ARQ Designs Limited | Wholesale & retail | 2018 |
| Arrampica Limited | Arts & recreation | 2002 |
| Arreton Mead Management Company Limited | Households | 1998 |
| Arrow Heating Ltd | Construction | 2019 |
| Arrow Legal Ltd | Professional & scientific | 2017 |
| Arrow Roofing Services Ltd | Construction | 2022 |
| Arrus Knoble Limited | Administrative & support | 2012 |
| Arsh Consulting Ltd | Wholesale & retail | 2024 |
| Arstorms Ltd | Wholesale & retail | 2021 |
| Art Angel Creations Ltd | Arts & recreation | 2019 |
| Art Native Ltd | Information & communication | 2022 |
| Art Research Creativity & Health | Health & social care | 1992 |
| Arta Travel Ltd | Transport & logistics | 2018 |
| Artfell Ltd | Real estate | 2013 |
| Arthur's Bridge Garage Limited | Wholesale & retail | 2001 |
| Artington Services Limited | Professional & scientific | 2012 |
| Artisan Fit Limited | Wholesale & retail | 2023 |
| Artisan Property & Investment Co. Limited | Construction | 1958 |
| Artists Rifles Clubhouse Events Limited | Arts & recreation | 2007 |
| Artists Rifles Clubhouse Ltd | Extraterritorial | 2006 |
| Artpart Limited | Construction | 2015 |
| Arts & Entertainment Productions Ltd | Arts & recreation | 2011 |
| Arvosta Limited | Professional & scientific | 2025 |
| AS Consultants International Ltd | Information & communication | 2025 |
| AS Dream House Ltd | Construction | 2020 |
| AS Landscapes Design & Build Ltd | Administrative & support | 2019 |
| AS Merchants Ltd | Transport & logistics | 2021 |
| AS Tiling Surrey Ltd | Construction | 2022 |
| Asahi Europe & International Ltd | Professional & scientific | 2017 |
| Asas Electrical Ltd | Construction | 2025 |
| Asasa Properties Limited | Real estate | 2020 |
| Asbestos Away OK Ltd | Water & waste | 2020 |
| Asde Limited | Extraterritorial | 2011 |
| Aselvia Marketing Limited | Information & communication | 2022 |
| ASH Cars Woking Limited | Wholesale & retail | 2026 |
| Ashamber Homes Limited | Health & social care | 2005 |
| Ashbell House Limited | Health & social care | 2001 |
| Ashbren Limited | Health & social care | 2013 |
| Ashbridge House Limited | Health & social care | 2000 |
| Ashbrook House Limited | Health & social care | 1998 |