| Andrew Montgomery Limited | Agriculture & fishing | 1988 |
| Andrew Wittich Architects Limited | Professional & scientific | 2014 |
| Andrews Wildlife Consultants Ltd | Professional & scientific | 2019 |
| Andrzej Ltd | Transport & logistics | 2022 |
| Andy Chance Home Improvements Ltd | Construction | 2026 |
| Andys Engineers Mildura PTY. Limited | | 2023 |
| Angel Care Services Ltd | Health & social care | 2021 |
| Angel TIP Limited | Hospitality | 2022 |
| Angela Hirst Surveyors & Valuers Limited | Administrative & support | 2005 |
| Angie Collins Business Consultancy & Coaching Ltd | Administrative & support | 2020 |
| Anglian Tectonics (Downlands) Limited | Construction | 1984 |
| Anglian Tectonics (Kent) Limited | Construction | 1984 |
| Anglo French Team Limited | Arts & recreation | 2007 |
| Anima Sound Productions Limited | Information & communication | 2003 |
| Anko Capital Ltd | Construction | 2025 |
| ANN Forrest Design Ltd | Professional & scientific | 2025 |
| Annalix Ltd | Health & social care | 2019 |
| Annealing Pro Ltd | Wholesale & retail | 2023 |
| Ansari Real Estate Ltd | Real estate | 2025 |
| Anslow K Limited | Wholesale & retail | 2016 |
| Anthony Builders Ltd | Construction | 2017 |
| Anthony L.Young Limited | Wholesale & retail | 1961 |
| Anthony Sarjeant Fine Wines Limited | Administrative & support | 2013 |
| Anthronexus Ltd | Professional & scientific | 1999 |
| Antony Meire Associates Limited | Professional & scientific | 2012 |
| Anywhere Creative Ltd | Arts & recreation | 2018 |
| Aoci Consultants Limited | Professional & scientific | 2000 |
| AP Carpentry & Renovations Ltd | Manufacturing | 2025 |
| AP Development Consultants Ltd | Administrative & support | 2018 |
| Apertana Limited | Professional & scientific | 2025 |
| Apex Pipelines Limited | Professional & scientific | 2021 |
| Apex Robotics Limited | Information & communication | 2026 |
| APH Consulting Ventures Ltd | Education | 2025 |
| Apollo U.K. Ltd | Financial services | 2024 |
| Apotec Ltd | Information & communication | 2020 |
| Apoyo Architects Ltd | Professional & scientific | 2022 |
| Appeak Ltd | Information & communication | 2020 |
| Appleton Property Management Limited | Real estate | 2000 |
| Applied Real Estate Technologies Limited | Professional & scientific | 2019 |
| Applied Relational Technology Limited | Information & communication | 1981 |
| Apptitude Consulting Ltd | Information & communication | 2016 |
| APS Consultancy Ltd | Financial services | 2014 |
| APV Films Limited | Information & communication | 2001 |
| APX Architecture Ltd | Professional & scientific | 2019 |
| APX Project Management Ltd | Construction | 2020 |
| Aqix Ltd | Professional & scientific | 1998 |
| Aqmen AI Limited | Information & communication | 2024 |
| Aqua Roofing Limited | Construction | 2002 |
| Aquasof Softeners & Salt Limited | Wholesale & retail | 2016 |
| Aquasoftuk Ltd | Wholesale & retail | 2019 |
| AR Consultancy Solutions Ltd | Professional & scientific | 2026 |
| AR Group Ventures Limited | Information & communication | 2025 |
| AR Hopper Ltd | Wholesale & retail | 2023 |
| AR Sports Operations Limited | Information & communication | 2025 |
| AR Swift Ltd | Wholesale & retail | 2026 |
| ARA Environmental Solutions Limited | Professional & scientific | 2013 |
| Aras Food Ltd | Hospitality | 2023 |
| ARC Graphics LLP | | 2021 |
| Arcade Cars Ltd | Wholesale & retail | 2020 |
| Arch Technology Ltd | Information & communication | 2021 |
| Archangel Distilleries Ltd | Manufacturing | 2016 |
| Archgate Wealth Ltd | Financial services | 2025 |
| Archibald Legacy Limited | Administrative & support | 2026 |
| Arclian Ltd | Arts & recreation | 2020 |
| Arcspeed Digital Solutions Ltd | Information & communication | 2017 |
| Arctic Cape Investments Limited | Administrative & support | 2022 |
| Arctic Hare Logistics Limited | Transport & logistics | 2022 |
| Arcturus Digital Limited | Information & communication | 2012 |
| Arcturus Holdings Limited | Professional & scientific | 2008 |
| Arcturus Publishing Limited | Information & communication | 1993 |
| Arden Court (Canterbury) Management Limited | Households | 1988 |
| Area X Ltd. | Information & communication | 2012 |
| Aren Foreign Trade Ltd | Wholesale & retail | 2023 |
| Arena Pictures Limited | Information & communication | 2008 |
| Arena Productions Ltd | Information & communication | 2026 |
| Arican Foreign Trade Consultancy Ltd | Wholesale & retail | 2019 |
| Arise Well Ltd | Professional & scientific | 2022 |
| Arjay Print Ltd | Administrative & support | 2010 |
| ARK Kent Limited | Other services | 2017 |
| ARK Textiles Ltd | Wholesale & retail | 2026 |
| ARM (Canterbury) Limited | Administrative & support | 2004 |
| ARN Brothers Ltd | Wholesale & retail | 2015 |
| ARO Paraplanning Limited | Administrative & support | 2025 |
| Arrow Health Economics Limited | Professional & scientific | 2024 |
| Arry Rail Limited | Construction | 2014 |
| ARS Private Ltd | Real estate | 2024 |
| Arsea Ltd | Real estate | 2016 |
| Art With a Social Pulse Ltd | Arts & recreation | 2025 |
| Artemis Psychology Ltd | Health & social care | 2018 |
| Arterra Limited | Professional & scientific | 2021 |
| Artifact Music Limited | Manufacturing | 2001 |
| Artisan Memorials Limited | Other services | 2019 |
| Artiwise UK Ltd. | Information & communication | 2023 |
| Arto Contracts Ltd | Administrative & support | 2022 |
| Arto Recruitment Ltd | Administrative & support | 2019 |
| Artwork Films Limited | Arts & recreation | 2001 |
| Arundel Collection Limited | Financial services | 2025 |
| Arvance Consulting Ltd | Professional & scientific | 2026 |
| Asbestos Drilling Services Ltd | Construction | 2023 |
| Ascendancy London Limited | Professional & scientific | 2016 |