| Arksoft Limited | Information & communication | 2014 |
| Arley Gardens Management Company Limited | Households | 2016 |
| Armchair Explorer Limited | Information & communication | 2022 |
| Armco Direct (Holdings) Ltd | Financial services | 2016 |
| Armco Direct Limited | Construction | 2005 |
| Armis Solutions Limited | Professional & scientific | 2025 |
| Armour (Midlands) Limited | Education | 2017 |
| Arms Production Music Limited | Information & communication | 2021 |
| Armstrong Bidco Limited | Financial services | 2018 |
| Armstrong Consultants Limited | Professional & scientific | 1993 |
| Armstrong Developments & Investments Ltd | Real estate | 2025 |
| Armstrong Midco Limited | Financial services | 2018 |
| Armstrong Sub-Holdings Limited | Financial services | 2018 |
| Armstrong Topco Limited | Financial services | 2018 |
| ARO 2 Ltd | Wholesale & retail | 2025 |
| ARQ Suppliers Limited | Wholesale & retail | 2025 |
| Art Azur Limited | Extraterritorial | 2018 |
| Art Strategic Land Limited | Real estate | 2026 |
| Artemis Financial Planning Limited | Financial services | 2025 |
| Arthur Capital Limited | Construction | 2022 |
| Arthur Civil Engineering Limited | Construction | 2017 |
| Arthur Consultancy Services Limited | Construction | 2021 |
| Arthur Developments 2 Limited | Real estate | 2021 |
| Arthur Group Holdings Limited | Financial services | 2025 |
| Arthur Group Property Limited | Real estate | 2025 |
| Arthur Meica Limited | Construction | 2024 |
| Artificial Lawn Solutions Ltd | Administrative & support | 2019 |
| Arts Health and Wellbeing CIC | Health & social care | 2024 |
| Artspace Loughborough Limited | Arts & recreation | 2011 |
| Artymys Limited | Real estate | 2022 |
| Arwina Food Limited | Hospitality | 2025 |
| ARY and Sheena Saaman Ltd | Professional & scientific | 2020 |
| Asap Promo Ltd | Professional & scientific | 2008 |
| ASD Support Ltd | Health & social care | 2019 |
| ASH Developments (Nottingham) Limited | Construction | 2018 |
| ASH Gordon Property Ltd | Construction | 2016 |
| Asha House Management Company Limited | Households | 2007 |
| Ashby Accounting Limited | Extraterritorial | 2008 |
| Ashby Chemical Co. Ltd. | Manufacturing | 1990 |
| Ashby Maintenance Limited | Administrative & support | 2014 |
| Ashby Mini Market Ltd | Wholesale & retail | 2024 |
| Ashby Road Mini Market Ltd | Wholesale & retail | 2026 |
| Asher Facilities Ltd | Construction | 2024 |
| Ashgate Consulting Limited | Professional & scientific | 2020 |
| Ashley Hall Plumbing Ltd | Construction | 2024 |
| Ashton Lees Limited | Real estate | 2007 |
| Asio Ecology LLP | | 2023 |
| ASJ Truck Mount Hire Ltd | Administrative & support | 2024 |
| ASK Accountancy Limited | Professional & scientific | 2003 |
| Asmar Limited | Construction | 2012 |
| ASP Marketing Limited | Professional & scientific | 2018 |
| Aspect (Charnwood) Ltd | Real estate | 2003 |
| Aspects Engineering (Control & Automation) Limited | Manufacturing | 2020 |
| Aspects Engineering Limited Liability Partnership | | 2009 |
| Asperry Limited | Professional & scientific | 2023 |
| Aspire :Lifeskills | Education | 2007 |
| Aspire Care Solutions Recruitment Limited | Administrative & support | 2025 |
| Aspire Fine Jewellery Limited | Wholesale & retail | 2012 |
| Aspire Scaffolding (Leicester) Ltd | Construction | 2025 |
| Aspire Scaffolding (Midlands) Ltd | Construction | 2021 |
| Asqa Limited | Hospitality | 2025 |
| Assett Ltd | Professional & scientific | 2021 |
| Assign Property Limited | Real estate | 2025 |
| Assisted Medicare Properties Limited | Construction | 2025 |
| Assisted Medicare Services Limited | Health & social care | 2023 |
| Association for Mathematics in Education | Other services | 2006 |
| Association for the Study of Obesity | Professional & scientific | 2003 |
| Association of Certified Non-Executive Directors | Other services | 2025 |
| Assured Civil Design Services Limited | Professional & scientific | 2019 |
| Assured Nova Limited | Real estate | 2025 |
| AST Lettings Limited | Real estate | 2009 |
| Astley Business Consulting Limited | Professional & scientific | 2023 |
| Astroclothes Limited | Wholesale & retail | 2026 |
| Astropace Limited | Arts & recreation | 2024 |
| Astute Chemical Development Consulting Limited | Professional & scientific | 2014 |
| Asyst UK Bidco Limited | Financial services | 2022 |
| Asyst UK Midco Limited | Financial services | 2022 |
| Asyst UK Topco Limited | Financial services | 2022 |
| AT & CL Brown Construction Limited | Construction | 2006 |
| AT CMC Solutions Limited | Professional & scientific | 2011 |
| AT Global Limited | Extraterritorial | 2012 |
| AT Home by Laura Ltd | Wholesale & retail | 2024 |
| At-Tarteel Ltd | Education | 2021 |
| ATG International Holdings Limited | Wholesale & retail | 2020 |
| ATG International Limited | Wholesale & retail | 2020 |
| Atkinson & Associates Ltd | Professional & scientific | 2019 |
| Atkinson Acoustics Limited | Professional & scientific | 2017 |
| Atlantic South West Ltd | Hospitality | 2025 |
| Atlantis Fish Shop Limited | Hospitality | 2025 |
| Atlas Retail Limited | Professional & scientific | 2009 |
| Atol Limited | Manufacturing | 1991 |
| Atol Racking and Buildings Limited | Manufacturing | 1990 |
| Attari Properties Ltd | Real estate | 2024 |
| Attracktion Limited | Arts & recreation | 2025 |
| Aucott Properties Ltd | Real estate | 2019 |
| Auction Salerooms Limited | Wholesale & retail | 2018 |
| Audacter Consultancy Limited | Information & communication | 2014 |
| Audiolite (UK) Ltd | Construction | 2013 |
| Augin Tech Solutions Limited | Information & communication | 2025 |
| Augment Properties Limited | Real estate | 2021 |