| Amazing Polish Properties Ltd | Real estate | 2021 |
| AMC Rise Ltd | Health & social care | 2018 |
| Amega Sciences Limited | Manufacturing | 1984 |
| Amivi Ltd | Professional & scientific | 2024 |
| Amore by RAE Limited | Other services | 2025 |
| AN Finance Limited | Wholesale & retail | 2025 |
| Anamagus Inns Limited | Hospitality | 2022 |
| Andolite Daventry Limited | Financial services | 2026 |
| Andolite International Limited | Manufacturing | 2026 |
| Andrei Bogdan Transport Ltd | Transport & logistics | 2024 |
| Andrite Ltd | Professional & scientific | 2014 |
| Andro Surfaces Limited | Manufacturing | 2022 |
| Andy Ibbott Training Ltd | Education | 2019 |
| Aneca Management Services Limited | Professional & scientific | 1976 |
| Aneko Accounting Services Ltd | Professional & scientific | 2024 |
| Angel of Hope Company Ltd | Health & social care | 2013 |
| Angel of Hope Healthcare Ltd | Health & social care | 2023 |
| Angel.V Services Ltd | Transport & logistics | 2013 |
| Anglian Service International Ltd | Professional & scientific | 2025 |
| Anglo Earth Resourcing Ltd | Mining & quarrying | 1996 |
| Angry Badger Brewhouse Ltd | Wholesale & retail | 2021 |
| Angry Badger Gaming Ltd | Information & communication | 2021 |
| Anirajstores Limited | Wholesale & retail | 2022 |
| ANMAR1 Limited | Transport & logistics | 2014 |
| Ansa Parking Consultants Ltd | Professional & scientific | 2026 |
| Anthony Eydon Limited | Professional & scientific | 2026 |
| Antonia Wills Saddles Ltd | Manufacturing | 2023 |
| ANY Pond Limited | Extraterritorial | 2023 |
| AP Home Improvements (Daventry) Ltd | Construction | 2021 |
| Apex Center Development Limited | Professional & scientific | 2025 |
| Apex Edge Developments Ltd | Construction | 2025 |
| Apex Timber Imports Ltd | Manufacturing | 2026 |
| Apexo Co., Limited | Professional & scientific | 2010 |
| Appka Ltd | Wholesale & retail | 2021 |
| Applied Science (UK) Ltd | Wholesale & retail | 2014 |
| Apro Energy Trading Ltd | Professional & scientific | 2023 |
| Aqua Pure Vitality Ltd | Water & waste | 2023 |
| Aquacert Ltd | Administrative & support | 1994 |
| Aquaflames Spas Limited | Manufacturing | 2015 |
| AR Wright Holdings Ltd | Financial services | 2025 |
| ARB Build Ltd | Construction | 2025 |
| Arbscape Tree Consultancy Ltd | Agriculture & fishing | 2022 |
| Arbscape Tree Surgeons Ltd | Agriculture & fishing | 2022 |
| Arcalot Holdings Ltd | Professional & scientific | 2015 |
| Arden Grace Interiors Limited | Professional & scientific | 2025 |
| Argeia Consulting Ltd | Professional & scientific | 2022 |
| Argenti Motorsport Ltd | Professional & scientific | 2019 |
| Argenti Racing Ltd | Arts & recreation | 2024 |
| ARM Build Ltd | Construction | 2020 |
| Arroyo UK International Trade Ltd. | Professional & scientific | 2010 |
| Art Angels (England) Limited | Wholesale & retail | 2020 |
| Asenware Ltd. | Professional & scientific | 2008 |
| Ashbro Composites Ltd | Professional & scientific | 2026 |
| Ashby Farms Power Limited | Energy | 2013 |
| Ashdc Ltd | Professional & scientific | 2024 |
| Ashley James Property Ltd | Real estate | 2026 |
| Ashworth Court Daventry Limited | Real estate | 2016 |
| Asia Pharmparter Co., Ltd. | Wholesale & retail | 2008 |
| Asiaflow Ltd | Wholesale & retail | 2024 |
| Asmolatin Limited | Information & communication | 2021 |
| Assertive Ltd | Construction | 2025 |
| Asset Engineering Services Limited | Construction | 2018 |
| Asset Servicing and Maintenance Ltd | Construction | 2020 |
| Asteria Beauty & Aesthetics Ltd | Other services | 2021 |
| Astrum Associates Limited | Professional & scientific | 2007 |
| Astute Engineering Ltd | Construction | 2025 |
| Asun Laboratory Limited | Professional & scientific | 2011 |
| AT Copperworks Ltd | Construction | 2018 |
| AT Your Door Limited | Administrative & support | 2024 |
| Ataraxia Soul Food Ltd | Hospitality | 2016 |
| Atat Properties Ltd | Real estate | 2023 |
| Atelier Equine Ltd | Agriculture & fishing | 2024 |
| Atkins & Co. Connections Ltd | Financial services | 2025 |
| Atlantico Intelligent Limited | Manufacturing | 2020 |
| Atlas Facilities Ltd | Real estate | 2015 |
| Atomisation Limited | Wholesale & retail | 2003 |
| Attlefield Farm Machinery Ltd | Wholesale & retail | 2009 |
| Audi International Commodities Ltd | Wholesale & retail | 2025 |
| August Engineering Ltd | Wholesale & retail | 2018 |
| Auto Door Repairs Limited | Other services | 2013 |
| Autodrome Limited | Extraterritorial | 2020 |
| Autogreen Limited | Water & waste | 2004 |
| Automation Technology Limited | Professional & scientific | 2001 |
| AV Euro Design Group Ltd | Construction | 2021 |
| Avandorr Ltd | Transport & logistics | 2018 |
| Avenger Couriers Ltd | Transport & logistics | 2022 |
| Avhm Ltd | Construction | 2021 |
| Avrol GB Ltd | Construction | 2025 |
| AWB Contracting Limited | Information & communication | 2003 |
| Axess International Limited | Wholesale & retail | 1986 |
| Axon Public Safety UK Limited | Wholesale & retail | 2010 |
| Ayrshire Metals Ltd | Manufacturing | 2015 |
| AZS Automotive Limited | Wholesale & retail | 2026 |
| B & K Bunting & SON Ltd | Construction | 2009 |
| B - Tech International Limited | Wholesale & retail | 1972 |
| B Building Ltd | Construction | 2022 |
| B Cheeky Ltd | Wholesale & retail | 2023 |
| B Reynolds Ltd | Financial services | 2025 |
| B-Independent Therapy Ltd. | Health & social care | 2018 |
| B-Tech AV Mounts Corporation Ltd | Financial services | 2022 |