| Anroja Ltd | Wholesale & retail | 2025 |
| Ansell Drainage Ltd | Construction | 2022 |
| Ansell Property Holdings Ltd | Real estate | 2026 |
| ANT Neuro UK Limited | Manufacturing | 2015 |
| Antagrade Electrical Limited | Construction | 1983 |
| Anthony Devine (Investments) Limited | Real estate | 2022 |
| Anthony Hull Limited | Information & communication | 2016 |
| Anthony Joseph & Co. Limited | Professional & scientific | 2012 |
| Anthony Pitt & Bond Limited | Real estate | 2022 |
| Antler Wood Limited | Extraterritorial | 2025 |
| Antn Projects Ltd | Construction | 2022 |
| ANY Kitchen Limited | Wholesale & retail | 2014 |
| Anyam Limited | Professional & scientific | 2016 |
| Anytyre.Com Ltd | Wholesale & retail | 2018 |
| AOG Consultancy Limited | Information & communication | 2017 |
| AOG Support Limited | Extraterritorial | 2015 |
| AOM Assets Limited | Wholesale & retail | 2025 |
| AP Engineering Enterprise Ltd | Administrative & support | 2026 |
| AP Pipefitting Ltd | Construction | 2017 |
| APA Construction Ltd | Construction | 2026 |
| APA Contract Services Limited | Administrative & support | 2013 |
| Apache Solutions Limited | Manufacturing | 1986 |
| Aparna Limited | Information & communication | 2010 |
| Aperture Way Ltd | Information & communication | 2026 |
| Apex Architectural Glazing Ltd | Manufacturing | 2024 |
| Apex Art Services Limited | Arts & recreation | 2005 |
| Apex Cambridge Lets Limited | Real estate | 2023 |
| Apex Cambridge Lettings Ltd | Other services | 2024 |
| Apex Cambridge Management Limited | Administrative & support | 2025 |
| Apex Cambridge Properties Ltd | Real estate | 2023 |
| Apex Landscapes & Patios Ltd | Administrative & support | 2026 |
| Apex PE and Sport Limited | Arts & recreation | 2018 |
| Apex Peterborough Properties Limited | Other services | 2022 |
| Apex Serviced Lets Limited | Other services | 2021 |
| Apex UK Lettings Ltd | Other services | 2024 |
| Apex UK Properties Ltd | Real estate | 2017 |
| Apex UK Properties Management Ltd | Real estate | 2017 |
| Apex UK Services Limited | Other services | 2019 |
| Apexar Ltd | Information & communication | 2026 |
| Aplin Consultancy Ltd | Professional & scientific | 2017 |
| Aplus Frederick and Associates Ltd | Administrative & support | 2021 |
| APM Property Refurbishments Ltd | Construction | 2008 |
| Apollo Living Spaces Ltd | Hospitality | 2022 |
| Apollo Marketing Solutions Ltd | Other services | 2019 |
| Apollo Pretium Limited | Other services | 2022 |
| Appeal Properties Limited | Real estate | 2017 |
| Appletrees Management Limited | Households | 1979 |
| Appliance Angels Ltd | Other services | 2012 |
| Applied Exomics Ltd | Professional & scientific | 2012 |
| Applied Procurement Ltd | Administrative & support | 2020 |
| Apsley Developments Limited | Real estate | 1997 |
| Aptitude Fitness HQ Ltd | Other services | 2022 |
| APW Group Ltd | Financial services | 2025 |
| Aqua Engineering Services Ltd | Professional & scientific | 2025 |
| Aqua Fiat Ltd. | Extraterritorial | 2016 |
| Aquacraft Plumbing Ltd | Households | 2026 |
| Aquamaintenance Limited | Construction | 2013 |
| Aquania Consultancy Limited | Professional & scientific | 2014 |
| Aquarius Worthington Ltd | Real estate | 2024 |
| Aquason Ltd | Wholesale & retail | 2024 |
| Aquastone Properties Limited | Real estate | 2022 |
| Aquatec Pools Ltd | Construction | 2026 |
| Aquilina Enterprise Ltd | Health & social care | 2015 |
| Aquinix Solutions Ltd | Information & communication | 2025 |
| AR Foods Stevenage Ltd | Hospitality | 2023 |
| AR Simply Electrical Ltd | Manufacturing | 2019 |
| Aramik Trading Company UK Ltd | Wholesale & retail | 2025 |
| Aran Energy Funding Limited | Administrative & support | 2016 |
| Aran Energy Holdings Limited | Financial services | 2017 |
| Aran Group Holdings Limited | Other services | 2019 |
| Aran Insulation Limited | Construction | 2012 |
| ARB Art & Design Ltd | Arts & recreation | 2023 |
| ARB Capital Limited | Information & communication | 2014 |
| Arbons Plumbing Limited | Construction | 2013 |
| ARC and BE Limited | Wholesale & retail | 2013 |
| ARC Locksmiths Ltd | Other services | 2013 |
| Arcadeimage Limited | Information & communication | 2023 |
| Arce UK Limited | Information & communication | 2017 |
| Arch Catering and Refrigeration Ltd | Manufacturing | 2021 |
| Arch Prep and Paint Ltd | Construction | 2024 |
| Archway Heating and Plumbing Services LLP | | 2024 |
| Archway Screenwriting Limited | Arts & recreation | 2021 |
| Arcimedia Limited | Information & communication | 2017 |
| Arckaingel Limited | Administrative & support | 2025 |
| Arcona Group Limited | Administrative & support | 2026 |
| Arctos Consulting Limited | Other services | 2024 |
| Ardeley Village Green Management Company Limited | Other services | 2011 |
| Ardent Media Productions Ltd | Information & communication | 2021 |
| Ardent PAY Partners Ltd | Administrative & support | 2024 |
| Ardentpower Ltd | Construction | 2019 |
| Area Fifty FUN Limited | Wholesale & retail | 2023 |
| Area Flooring Limited | Construction | 2018 |
| Arendt OWL II Limited | Professional & scientific | 2023 |
| Arete Project Management Ltd | Professional & scientific | 2019 |
| ARG General Construct Ltd | Construction | 2024 |
| Argent Advancements Limited | Administrative & support | 2020 |
| Arges Engineering Limited | Professional & scientific | 2021 |
| Aria Residential Care Newton House Ltd | Health & social care | 2025 |
| Ariaye Limited | Health & social care | 2013 |
| Arion Property Limited | Real estate | 2013 |