| Albatraoz Limited | Professional & scientific | 2024 |
| Alberca 1991 Limited | Real estate | 2019 |
| Albert Close Property Management Limited | Real estate | 2000 |
| Albi Cleaning Services Ltd | Administrative & support | 2023 |
| Albin & Co. Limited | Professional & scientific | 2013 |
| Albion Place (Newbury) Management Company Limited | Households | 2004 |
| Albs & Elms Limited | Manufacturing | 2026 |
| Albuhera Investment Group Limited | Wholesale & retail | 1998 |
| Albury Place (Kidmore END Road) Residents Management Company Limited | Households | 2007 |
| Alchemist Developments Ltd | Real estate | 2024 |
| Alchemy Coach Academy Ltd | Health & social care | 2008 |
| Alchemy Furniture Limited | Manufacturing | 2009 |
| Alchemy Process Solutions Ltd | Administrative & support | 2007 |
| Aldbrough Pathfinder Limited | Energy | 2023 |
| Alder Bridge Association for Steiner-Waldorf Education | Education | 1987 |
| Alder Tree (Home Education Centre) CIC | Education | 2022 |
| Alder Tree Consulting Ltd | Professional & scientific | 2011 |
| Aldermaston Services Limited | Agriculture & fishing | 2020 |
| Aldermore Bank PLC | Financial services | 1969 |
| Aldermore Group PLC | Financial services | 2008 |
| Aldermore Invoice Finance (Holdings) Limited | Extraterritorial | 2009 |
| Aldermore Invoice Finance (Oxford) Limited | Extraterritorial | 1987 |
| Aldermore Invoice Finance Limited | Extraterritorial | 1990 |
| Aldridge Landscaping Limited | Construction | 2017 |
| Aldworth Brewing Company Ltd | Manufacturing | 2021 |
| Aldworth Inns Limited | Hospitality | 2008 |
| Aldworth Intelligence Limited | Administrative & support | 2023 |
| Aldworth Rise Forecourt Ltd | Households | 2019 |
| Alebrije Consulting Ltd | Extraterritorial | 2020 |
| Alec Dresden (UK) Limited | Professional & scientific | 2023 |
| Alef Foods Limited | Hospitality | 2024 |
| Aleksander Oliver Property Services Ltd | Real estate | 2021 |
| Alem Property Ventures Ltd | Real estate | 2025 |
| Alessia Nyah Ltd | Information & communication | 2023 |
| Alex Igov Services Ltd | Construction | 2019 |
| Alex Newton Ltd | Wholesale & retail | 2023 |
| Alex Walters Consultancy Limited | Health & social care | 2012 |
| Alexander and Nicholas Courts Management Limited | Households | 1979 |
| Alexander Foster Fine Art Ltd | Wholesale & retail | 2016 |
| Alexander Preston Estates Limited | Extraterritorial | 2017 |
| Alexander Ross ARB Holdings Ltd | Financial services | 2026 |
| Alexander Rowan Financial Limited | Financial services | 2015 |
| Alexander Rowan LLP | | 2004 |
| Alexander Worldwide Shipping & Removals Limited | Transport & logistics | 2008 |
| Alexander Worth Ltd | Financial services | 1996 |
| Alexandra Estate Management Ltd | Real estate | 2011 |
| Alexandra Residents Management Company Limited | Households | 1990 |
| Alfa AID Ltd | Wholesale & retail | 2003 |
| Alfa Construct Ltd | Construction | 2012 |
| Alfadelta Ltd | Transport & logistics | 2021 |
| Alfajazz.Investments Ltd | Wholesale & retail | 2023 |
| Alfavita Ltd | Information & communication | 2026 |
| Alfie Homes Ltd | Construction | 2024 |
| Alfred M Building Services Ltd | Construction | 2025 |
| Algerie Advice C Ltd | Information & communication | 2020 |
| Algolia Limited | Information & communication | 2017 |
| Algovet Ltd | Wholesale & retail | 2021 |
| ALI Ahmad Goods Ltd | Wholesale & retail | 2026 |
| ALI Construction Ltd | Construction | 2018 |
| ALI Hair and Beauty Limited | Health & social care | 2017 |
| ALI Ibrahim Ltd | Administrative & support | 2015 |
| ALI Ibrahim Properties Limited | Real estate | 2016 |
| ALI Properties Ltd | Real estate | 2025 |
| Alia Smile Ltd | Health & social care | 2021 |
| Alica Limited | Wholesale & retail | 2005 |
| Alice Designs Limited | Professional & scientific | 1988 |
| Alice’S Wonderbands Ltd | Manufacturing | 2020 |
| Alicia Draws Ltd | Arts & recreation | 2026 |
| Alida Inc Limited | Wholesale & retail | 2026 |
| Alifa Consultants Ltd | Information & communication | 2006 |
| Alifa Estates Limited | Real estate | 2017 |
| Align'D Wellness Limited | Wholesale & retail | 2026 |
| Aligne Pilates Studio Ltd | Arts & recreation | 2025 |
| Alike Group Limited | Wholesale & retail | 2018 |
| Alina Gruia Ltd | Health & social care | 2014 |
| Alingoz Limited | Other services | 2026 |
| Aliseni Brothers Limited | Real estate | 2017 |
| Alitec Ltd | Wholesale & retail | 2018 |
| Ality Ltd | Professional & scientific | 2015 |
| Aliyna Limited | Public administration | 2024 |
| Alizeti Creative Exchange Limited | Other services | 2026 |
| Alk-Abello Limited | Wholesale & retail | 1999 |
| Alka Super Store Ltd | Wholesale & retail | 2020 |
| Alkaline Your Lifestyle Ltd | Wholesale & retail | 2021 |
| ALL About Carbon Ltd | Professional & scientific | 2019 |
| ALL About Results Limited | Professional & scientific | 2005 |
| ALL Aspects Pest Control Limited | Administrative & support | 2016 |
| ALL Building Maintenance Limited | Administrative & support | 2025 |
| ALL Cool Services Ltd | Administrative & support | 2016 |
| ALL Counties Holdings Ltd | Hospitality | 2019 |
| ALL Drain Services Ltd | Water & waste | 2025 |
| ALL Effects Limited | Information & communication | 2004 |
| ALL Electrics and Building Management Limited | Construction | 2017 |
| ALL Four Engineering Limited | Wholesale & retail | 2025 |
| ALL in One Go Ltd | Administrative & support | 2024 |
| ALL in Services (Hampshire) Limited | Wholesale & retail | 2003 |
| ALL in Touch Ltd | Information & communication | 2026 |
| ALL Maintenance Services Ltd. | Administrative & support | 2016 |
| ALL Occupation Services Ltd | Transport & logistics | 2023 |
| ALL Opal Ltd | Wholesale & retail | 2018 |