| Alltechtraining Limited | Information & communication | 2025 |
| Almond-Blossoms Events Ltd | Administrative & support | 2010 |
| Alpha BMC Limited | Construction | 2014 |
| Alpharm Trading Limited | Administrative & support | 2016 |
| Alston Partners Consulting Limited | Professional & scientific | 2025 |
| ALT Consulting Services Limited | Professional & scientific | 2026 |
| Always Believe in Miracles Ltd | Wholesale & retail | 2026 |
| Amastic Construction Limited | Construction | 2023 |
| Amastic Roofing, Building & Scaffolding Services Ltd | Construction | 2013 |
| Amazontee Limited | Manufacturing | 2004 |
| Ambershire Holdings Limited | Extraterritorial | 2025 |
| Ambershire Limited | Agriculture & fishing | 1976 |
| Ambrose Creative Ltd | Professional & scientific | 2014 |
| Amca Belle Trailers Ladies and Girls Trials Championship Limited | Arts & recreation | 2025 |
| Amerdale IT Limited | Information & communication | 2011 |
| AMI Access Solutions Limited | Manufacturing | 2023 |
| Ammonite Technical Solutions Limited | Administrative & support | 2024 |
| Amnis Homes Limited | Real estate | 2018 |
| Amroco Group Limited | Wholesale & retail | 2016 |
| Amy-Jo Simpson Limited | Professional & scientific | 2022 |
| AN Artful Life Limited | Wholesale & retail | 2022 |
| Andrew Allen Limited | Administrative & support | 2007 |
| Andrew Banks Trading Limited | Wholesale & retail | 1998 |
| Andrewsfieldflightstudio Ltd | Education | 2020 |
| Andy Griffin Photography Ltd | Professional & scientific | 2008 |
| Anglian Land Drainage Limited | Administrative & support | 1997 |
| Anntina Carpentry and Building Limited | Construction | 2023 |
| Anomalies Limited | Real estate | 2000 |
| Anthea Thornton Occupational Therapy Services Limited | Health & social care | 2013 |
| Anthony and Nicholas Limited | Wholesale & retail | 2019 |
| AOF Building Services Limited | Construction | 2024 |
| Apeiro Advisory & Business Solutions Limited | Professional & scientific | 2020 |
| Apeiro Technology Solutions Limited | Information & communication | 2022 |
| Apfb Limited | Real estate | 2026 |
| APM GAS and Heating Limited | Administrative & support | 2015 |
| Apollo Swim Limited | Manufacturing | 2024 |
| Appletree Analogue Limited | Information & communication | 2019 |
| APS Computing Limited | Information & communication | 2018 |
| APS Supplier Ltd | Wholesale & retail | 2024 |
| APT21 Fire Safety Ltd | Professional & scientific | 2025 |
| Aquasam Limited | Professional & scientific | 2017 |
| Aquavista Limited | Professional & scientific | 2007 |
| Arba Consultancy (UK) Ltd | Professional & scientific | 2005 |
| Architectural Design Studio Ltd | Professional & scientific | 2022 |
| Ardeley Faraday Limited | Extraterritorial | 2020 |
| Argent Street "D" Management Limited | Households | 1987 |
| Argonaught Network Technologies Limited | Wholesale & retail | 2000 |
| Argy Design & Consultants Limited | Administrative & support | 2012 |
| Arke Consulting Limited | Information & communication | 2013 |
| ARM Abodes Limited | Real estate | 2023 |
| Armadillo Customs Ltd | Manufacturing | 2020 |
| Armadillo Marketing Limited | Manufacturing | 1996 |
| Armark Group Ltd | Manufacturing | 2024 |
| Armoured 4X4 Ltd | Wholesale & retail | 2022 |
| Armourtec Property Maintenance Limited | Construction | 2018 |
| Armourtec Security & Electrical Limited | Construction | 2011 |
| Arnold & Arnold Co. Limited | Manufacturing | 1982 |
| ASH and Stone Ltd | Administrative & support | 2025 |
| ASH Tree Retail Services Limited | Wholesale & retail | 2016 |
| Ashmah Ltd | Real estate | 2025 |
| Ashwood ARB Ltd | Agriculture & fishing | 2026 |
| Aslan 75 Limited | Real estate | 2025 |
| Asori UK Ltd | Wholesale & retail | 2023 |
| ATE Trans Ltd | Transport & logistics | 2020 |
| Athens Corporate Limited | Professional & scientific | 2013 |
| Athleticdev Ltd | Arts & recreation | 2023 |
| ATK Insulations Limited | Construction | 2013 |
| Atkins Capital Limited | Financial services | 2013 |
| ATM Solar Ltd | Construction | 2024 |
| Atworth Limited | Real estate | 2016 |
| Audio Genius Ltd | Information & communication | 2026 |
| Aurea Tanning Ltd | Other services | 2026 |
| Aurora Building Services Limited | Construction | 2025 |
| Autocoffee Ltd | Hospitality | 2023 |
| Autonomy Four Properties Limited | Real estate | 2018 |
| Autos Kraal Ltd | Wholesale & retail | 2025 |
| Autumn Falls Music Productions Limited | Information & communication | 2024 |
| Avatar (UK) Limited | Information & communication | 1997 |
| Averon Scaffolding Limited | Construction | 2022 |
| Aviation Advisory Services Limited | Professional & scientific | 2022 |
| Aviation Safety Initiatives Limited | Professional & scientific | 2013 |
| Avus Property Limited | Real estate | 2025 |
| Aweid Knee Clinic Limited | Health & social care | 2022 |
| AWM General Aviation Limited | Arts & recreation | 2015 |
| AWM Group of Companies Limited | Financial services | 2016 |
| AWM Technologies Limited | Extraterritorial | 2014 |
| AWS (UK) Limited | Professional & scientific | 2014 |
| Aztec Property Repairs Ltd | Water & waste | 2010 |
| Azure Capital Group Limited | Financial services | 2019 |
| B.B. Grounds Care Limited | Administrative & support | 2002 |
| B.I.G. Consultancy Limited | Water & waste | 2013 |
| B.M. & D.V. Rutterford Limited | Agriculture & fishing | 1958 |
| Back River Management Ltd | Professional & scientific | 2022 |
| Badger Commissioning Limited | Wholesale & retail | 1997 |
| Bailey Site Solutions Limited | Construction | 2025 |
| Baker & Metson Limited | Agriculture & fishing | 1960 |
| Bakerpierce Ltd | Administrative & support | 1993 |
| Balance Your Brain Ltd | Education | 2023 |
| Ballers Group Limited | Administrative & support | 2020 |
| Balro Limited | Agriculture & fishing | 2000 |