| Appr Limited | Professional & scientific | 2018 |
| Appraise Fire Engineering Consultancy Limited | Professional & scientific | 2022 |
| Appraise Fire Group Limited | Financial services | 2026 |
| Apprentice Employment Agency Limited | Extraterritorial | 2011 |
| Approved Media Limited | Professional & scientific | 2006 |
| Appstation Limited | Information & communication | 1998 |
| Appt Online Solutions Ltd | Information & communication | 2013 |
| Apptimist Limited | Information & communication | 2015 |
| Appurtenance Limited | Other services | 2019 |
| April Bell Florist Limited | Financial services | 2018 |
| April Systems Limited | Administrative & support | 2018 |
| APS Management Consulting Limited | Professional & scientific | 2020 |
| Apsis Associates Ltd | Professional & scientific | 2014 |
| APT Metals Limited | Administrative & support | 2014 |
| APT-COVER24 Healthcare Limited | Health & social care | 2022 |
| Apt-Tech Solns Ltd | Information & communication | 2010 |
| Aptavision Limited | Health & social care | 2024 |
| Aptus 1 Holdco Limited | Real estate | 2025 |
| Aptus 1 Propco Limited | Real estate | 2025 |
| APW Finance BP Ltd | Information & communication | 2019 |
| APW Property Investments Ltd | Wholesale & retail | 2024 |
| AQ Clean Ltd | Administrative & support | 2026 |
| AQ Projects Ltd | Construction | 2025 |
| AQH Micklegate (Acres Hill) Management Company Limited | Households | 2008 |
| Aqlios Healthcare Ltd | Health & social care | 2026 |
| Aqlios Primary Care Ltd | Health & social care | 2026 |
| Aqlios Property Ltd | Real estate | 2026 |
| Aqua Drain Solutions Ltd | Water & waste | 2014 |
| Aqua GAS Services Ltd | Construction | 2018 |
| Aqua Vita Capital Ltd | Financial services | 2023 |
| Aqua With Ashleigh Limited | Arts & recreation | 2018 |
| Aqua Zone (GB) Limited | Professional & scientific | 2010 |
| Aquability OPS Limited | Professional & scientific | 2015 |
| Aquaculture Transformation Limited | Agriculture & fishing | 2025 |
| Aquae Arnemetiae Vintage Tea Rooms & Wine Bar Ltd | Hospitality | 2024 |
| Aquafun Sheffield Limited | Manufacturing | 2010 |
| Aquaport UK Ltd | Wholesale & retail | 2023 |
| Aquascience Consultancy Limited | Agriculture & fishing | 2014 |
| Aquaslate Group Ltd | Administrative & support | 2024 |
| Aquatic Ventures Ltd | Wholesale & retail | 2023 |
| Aquavolt Limited | Construction | 2014 |
| Aquila 2000 Limited | Information & communication | 1997 |
| Aquila Consortium Limited | Wholesale & retail | 2026 |
| Aquilo Marketing Limited | Professional & scientific | 2024 |
| AR Dental Services Limited | Health & social care | 2024 |
| AR DON Estates Ltd | Real estate | 2026 |
| AR DON Holdings Ltd | Financial services | 2026 |
| AR Kiveton Spice Box Limited | Hospitality | 2024 |
| AR Law Consultancy Ltd | Professional & scientific | 2025 |
| AR Pharma Ltd | Health & social care | 2023 |
| AR Plumbtech Limited | Construction | 2023 |
| Ar&K (UK) Property Ltd | Hospitality | 2025 |
| ARA Advisory Group Ltd | Professional & scientific | 2026 |
| ARA IDE Limited | Manufacturing | 2022 |
| Araa Services Limited | Administrative & support | 2020 |
| Arabella Parabellum Properties Limited | Real estate | 2020 |
| Arabian Coffee Limited | Manufacturing | 2025 |
| Arabian Diner Limited | Hospitality | 2022 |
| Arabica Holding International Ltd | Hospitality | 2026 |
| Arafgroup Limited | Professional & scientific | 2025 |
| Aragsan Limited | Hospitality | 2025 |
| Aran Hand Carwash Ltd | Administrative & support | 2026 |
| Ararat Inns Ltd | Hospitality | 2025 |
| Aras Eats Ltd | Hospitality | 2024 |
| Arash Grill Ltd | Hospitality | 2024 |
| Arb-Store Ltd | Wholesale & retail | 2024 |
| Arbee Properties Limited | Real estate | 2024 |
| Arberi Construction Limited | Real estate | 2023 |
| Arborist Tree Care Ltd | Administrative & support | 2014 |
| Arborlow Homes LLP | | 2025 |
| Arbour Business Consultancy Limited | Professional & scientific | 2023 |
| Arbourthorne 60 Limited | Extraterritorial | 2014 |
| Arbs Resources Ltd | Construction | 2025 |
| Arbscope Ltd | Professional & scientific | 2023 |
| Arbtron Ltd | Administrative & support | 2025 |
| Arbtron Solutions Limited | Real estate | 2025 |
| ARC 3 Ltd | Education | 2026 |
| ARC Electrical Engineering Ltd | Professional & scientific | 2011 |
| ARC Living Ltd | Construction | 2026 |
| ARC Orthopaedics Ltd | Wholesale & retail | 2026 |
| ARC Project Management Ltd | Professional & scientific | 2025 |
| ARC Restoration Limited | Construction | 2023 |
| Arc-Rite Engineering Limited | Manufacturing | 2021 |
| Arcade Talent Agency Ltd | Arts & recreation | 2018 |
| Arcadia Landscape & Design Limited | Administrative & support | 2013 |
| Arcadyan Technology Limited | Wholesale & retail | 2016 |
| Arcaic Studios Ltd | Information & communication | 2024 |
| Arcane Sanctum Ltd | Households | 2025 |
| Arcelormittal Sheffield Limited | Manufacturing | 1988 |
| Arch 8 Trading Ltd | Real estate | 2019 |
| Arch Dental Laboratory Ltd | Manufacturing | 2015 |
| Arch Lifestyle Limited | Wholesale & retail | 2024 |
| Archangel Events Ltd | Arts & recreation | 2023 |
| Archangel Property Ltd | Real estate | 2023 |
| Archangel Property Specialists Limited | Financial services | 2024 |
| Archcourt Limited | Wholesale & retail | 1991 |
| Archer Clinical Ltd | Other services | 2019 |
| Archer Project Enterprises Ltd | Manufacturing | 2010 |
| Archer Real Estate Services Limited | Real estate | 2024 |
| Archer Studios Ltd | Information & communication | 2026 |