| ANT & FOX Homes Limited | Real estate | 2021 |
| Anthony Eamens Design Ltd | Professional & scientific | 2019 |
| Anthony James Consulting Limited | Information & communication | 2013 |
| Anthony Medical Limited | Real estate | 2013 |
| Antony Reeves Ltd | Arts & recreation | 2017 |
| Anumaha Limited | Real estate | 2024 |
| Anymed Ltd | Wholesale & retail | 2024 |
| Anytime Hands Ltd | Administrative & support | 2026 |
| AP Economics Consulting Services Ltd. | Professional & scientific | 2013 |
| AP Learning Independent Services Ltd | Education | 2020 |
| Apac Services Limited | Construction | 2007 |
| APB Plumbing & Heating Limited | Construction | 2019 |
| Apex Building Systems Limited | Wholesale & retail | 2024 |
| Apex Car & Van Rental Limited | Professional & scientific | 1995 |
| Apex Car Hire Limited | Professional & scientific | 1995 |
| Apex Car Rental (Eastbourne) Limited | Professional & scientific | 1995 |
| Apex Car Rental UK Limited | Extraterritorial | 2006 |
| Apex Construction Surrey Limited | Construction | 2025 |
| Apex Easifleet Limited | Professional & scientific | 2001 |
| Apex Easyfleet Limited | Professional & scientific | 2001 |
| Apex Progress Property UK Ltd | Real estate | 2025 |
| Apex Renovations Ltd | Construction | 2025 |
| Apex Rental Limited | Professional & scientific | 1995 |
| Apex Structural Engineers Limited | Professional & scientific | 2021 |
| Apex Travel Consulting Ltd | Administrative & support | 2017 |
| Aphex Investments Limited | Financial services | 2017 |
| Aphrodite Esthetics Ltd | Other services | 2015 |
| Apis Interim Management Limited | Professional & scientific | 2014 |
| APJ Limited | Information & communication | 1999 |
| Apks Ltd | Health & social care | 2024 |
| APM Fire Protection Limited | Public administration | 2015 |
| Aporta Ltd | Real estate | 2024 |
| App Damon Ltd | Information & communication | 2010 |
| Apphardware Limited | Information & communication | 2013 |
| Applegem Limited | Professional & scientific | 2008 |
| Applied Applications Limited | Professional & scientific | 2017 |
| APR Associates Limited | Real estate | 2009 |
| Apsley (Gartloch) Limited | Real estate | 2025 |
| Apsley Academy International Ltd | Education | 2020 |
| Apsley Bristol Limited | Real estate | 2022 |
| Apsley Connect LLP | | 2025 |
| Apsley Drive Limited | Construction | 2025 |
| Apsley House Management Limited | Real estate | 2016 |
| Apsley NO 2 Limited | Real estate | 2021 |
| APT Transport Ltd | Other services | 2020 |
| Aqua Pups Limited | Education | 2026 |
| Aqualite Solutions Ltd | Wholesale & retail | 2025 |
| Aquamarine Oriental Limited | Wholesale & retail | 1997 |
| Aquazen Ltd | Manufacturing | 2026 |
| Aquila Aeropower Ltd | Manufacturing | 2020 |
| AR Health & Beauty Limited | Administrative & support | 2010 |
| Araam Health Ltd | Manufacturing | 2026 |
| Arac Consulting Limited | Professional & scientific | 2017 |
| Aragon Solutions Ltd | Professional & scientific | 2016 |
| Arbity Holdings Limited | Real estate | 2018 |
| Arbity Limited | Real estate | 2018 |
| Arbity Property Limited | Real estate | 2018 |
| Arbury Estates Limited | Professional & scientific | 1995 |
| ARC Autos Limited | Wholesale & retail | 2010 |
| ARC Osteopathy and Health Limited | Health & social care | 2016 |
| Arch Property Maintenance Services Limited | Households | 2019 |
| Archer Leisure Limited | Arts & recreation | 1982 |
| Archers ROW Management Limited | Households | 2013 |
| Architon LLP | | 2004 |
| Architon Media Graphics Limited | Extraterritorial | 1987 |
| Archive Sourcing Ltd | Wholesale & retail | 2025 |
| Archmead Construction Limited | Construction | 1976 |
| Arcro Ltd | Professional & scientific | 2018 |
| Arcville Limited | Real estate | 2021 |
| Arfedor Ltd | Wholesale & retail | 2026 |
| Argon E-Commerce Ltd | Wholesale & retail | 2024 |
| Aria Cadogan House Limited | Professional & scientific | 2017 |
| Aria Development Management Limited | Professional & scientific | 2015 |
| Arik Time Ltd | Wholesale & retail | 2025 |
| Arista Court Management Company Limited | Households | 2006 |
| Aristeos Consulting Ltd | Professional & scientific | 2019 |
| ARK Accountancy Limited | Professional & scientific | 2022 |
| ARK Atlantic & Co Ltd | Professional & scientific | 2025 |
| ARK Enterprises Holding Limited | Financial services | 2026 |
| ARK Fashion Agency Limited | Wholesale & retail | 2019 |
| ARK Innovations Solutions Ltd | Other services | 2026 |
| ARK Leisure Management Limited | Health & social care | 1999 |
| ARK Orthotics Limited | Health & social care | 2025 |
| ARK Plus Care Ltd | Health & social care | 2026 |
| ARK Software Ltd | Information & communication | 2020 |
| Arkadius Limited | Professional & scientific | 2010 |
| Arkay Software Solutions Limited | Information & communication | 2010 |
| Arkmore Developments Ltd | Real estate | 2023 |
| Arkstone Construction Limited | Construction | 2024 |
| Arkstone Group Limited | Financial services | 2024 |
| ARM Tile Expert Ltd | Construction | 2025 |
| Armac Consulting Ltd | Information & communication | 2025 |
| Armadillo Music Limited | Information & communication | 1999 |
| Armalyte Industries Ltd | Arts & recreation | 2013 |
| ARN Tech Limited | Information & communication | 2024 |
| Arni Investments Limited | Real estate | 2024 |
| Arrowmek Consultants Ltd | Professional & scientific | 2025 |
| Art Resistance Limited | Information & communication | 2021 |
| Art-House-Life Ltd | Hospitality | 2024 |
| Art-K Ewell Ltd | Education | 2021 |