| ALU Pro Roofing & Building Ltd | Construction | 2024 |
| Alygn Media Ltd | Information & communication | 2025 |
| AM Source Limited | Information & communication | 2014 |
| Amalace Ltd | Information & communication | 2016 |
| Amaravathi Take Away Ltd | Hospitality | 2025 |
| Ambleside Services Ltd | Professional & scientific | 2009 |
| Ambrigs Ltd | Wholesale & retail | 2025 |
| AMD Technik Ltd | Extraterritorial | 2010 |
| Amigos Languages International Ltd | Education | 2016 |
| Amisten Consulting Limited | Information & communication | 2017 |
| Amor Properties Ltd | Real estate | 2026 |
| Analyzed Logic Ltd | Other services | 2014 |
| Anantara Property Limited | Real estate | 2023 |
| AND NOW WE Breathe Limited | Health & social care | 2022 |
| Andrew Seggins Limited | Information & communication | 2012 |
| Andy Newell Limited | Other services | 2000 |
| Angelo's Care Limited | Health & social care | 2021 |
| Angels Gardening Services Ltd | Administrative & support | 2019 |
| Aniafit Limited | Extraterritorial | 2024 |
| Anmut Consulting Ltd | Professional & scientific | 2018 |
| Anmut Ltd | Professional & scientific | 2018 |
| Annaleigh Place (Walton) Management Company Limited | Real estate | 2009 |
| Anniblemuirsmith Limited | Information & communication | 2026 |
| Antix Management Limited | Wholesale & retail | 2012 |
| Anwen Ashworth Limited | Education | 2015 |
| AOG Clinic Limited | Health & social care | 2016 |
| Apps Court Farm Ltd | Real estate | 2007 |
| Aqua South Ltd | Agriculture & fishing | 2026 |
| Aquaclean London Limited | Administrative & support | 2014 |
| AR14 UK Ltd | Professional & scientific | 2022 |
| Arbor Field Ltd | Professional & scientific | 2025 |
| ARCHIMEDIC5 Ltd | Health & social care | 2022 |
| Ardano Ltd | Information & communication | 2021 |
| Ardu Construction Ltd | Construction | 2017 |
| Arian Holdings Limited | Financial services | 2026 |
| Arian Property Investment Ltd | Real estate | 2023 |
| ARK Birch Customs Limited | Manufacturing | 2020 |
| Arlot Limited | Other services | 2023 |
| Armeya Ltd | Real estate | 2018 |
| Arslanbey Kebab Ltd | Hospitality | 2024 |
| Art DE Minuit UK Ltd | Manufacturing | 2025 |
| Art Definition Ltd | Professional & scientific | 2022 |
| Art in Marketing Ltd | Professional & scientific | 2024 |
| Artb PMS Ltd | Professional & scientific | 2013 |
| Artedomus Ltd | Wholesale & retail | 2025 |
| Artedomus Studio Ltd | Construction | 2025 |
| Arterial Developments Ltd | Real estate | 2025 |
| Artful Painters Limited | Construction | 2008 |
| Artowo Gallery Ltd | Wholesale & retail | 2026 |
| Arum 3D Solutions Ltd | Manufacturing | 2015 |
| Arum Implants Ltd | Manufacturing | 2023 |
| Arôme D’Ailleurs Ltd | Wholesale & retail | 2025 |
| Asan Holdings Ltd | Financial services | 2022 |
| Asan Investment 1 Ltd | Financial services | 2026 |
| Asan Investment 2 Ltd | Real estate | 2026 |
| Asbury Sewell Holdings Ltd | Financial services | 2023 |
| Ashcroft Interiors Ltd | Manufacturing | 2013 |
| Ashdwon Property Management Ltd | Households | 2025 |
| Ashley & Ace Cars Ltd | Transport & logistics | 2018 |
| Ashley MOT & Service Centre Limited | Wholesale & retail | 2010 |
| Ashoka Hersham Ltd | Hospitality | 2019 |
| Ashridge Holdings Limited | Construction | 1998 |
| Ashton Property Partnership Ltd | Real estate | 2025 |
| Aspect Floors Ltd | Construction | 2021 |
| Asranet Limited | Professional & scientific | 2022 |
| Associated 2 Digital UK Ltd | Information & communication | 2021 |
| Astor & Eden Ltd | Wholesale & retail | 2024 |
| Astraline Tools Ltd | Administrative & support | 1992 |
| Athena Physio Ltd | Health & social care | 2007 |
| Athene Leadership Coaching Ltd | Other services | 2019 |
| Athink Architects Ltd | Professional & scientific | 2020 |
| Atkins Care Services Limited | Health & social care | 2007 |
| Atkins Retail Ltd | Other services | 2016 |
| Atlas OS Ltd | Information & communication | 2026 |
| Audioexp Ltd | Information & communication | 2023 |
| Audley Firs Management Company Limited | Hospitality | 1983 |
| Auri Lifts Ltd | Manufacturing | 2025 |
| Auxbuss Ltd | Information & communication | 2011 |
| AV Wise Ltd | Information & communication | 2022 |
| Aviatech Consulting Ltd | Information & communication | 2025 |
| Azone Construction Ltd | Construction | 2024 |
| Azone Scaffolding Ltd | Construction | 2022 |
| B&R Steel & Formwork Ltd | Construction | 2024 |
| Babble Comms Ltd | Information & communication | 2013 |
| BAJ Developer Ltd | Real estate | 2024 |
| BAJ Real Estate Ltd | Real estate | 2024 |
| Balbus Investments Ltd | Real estate | 2020 |
| Bancroft Consult Ltd | Information & communication | 2025 |
| Bani & Bani Holdings Limited | Real estate | 2024 |
| Banns Advisors Ltd | Professional & scientific | 2024 |
| Banns Electrics Ltd | Construction | 2017 |
| Banyan Ltd | Real estate | 2025 |
| Barford Productions Limited | Information & communication | 1984 |
| Barkingaboutdogs Ltd | Other services | 2023 |
| Barnard Energy Consulting Ltd | Professional & scientific | 2025 |
| Barnton Park Group Ltd | Professional & scientific | 2023 |
| Barrell Properties Limited | Real estate | 2023 |
| Baseline Edge Ltd | Arts & recreation | 2025 |
| Bathroom Culture Ltd | Wholesale & retail | 2021 |
| Batlabs Limited | Information & communication | 2014 |