| Alfred Bagnall & Sons (Support Services) Limited | Administrative & support | 1972 |
| Alfred Bagnall & Sons (West) Limited | Construction | 1972 |
| Alfred Bagnall & Sons (York) Limited | Construction | 1989 |
| Alfred Bagnall and Sons Limited | Professional & scientific | 1911 |
| Aliz Consulting CIC | Professional & scientific | 2025 |
| Aliz GB Solutions Ltd | Other services | 2018 |
| Aliz Group Ltd | Professional & scientific | 2025 |
| ALL - Printed Limited | Manufacturing | 2020 |
| ALL About Upvc Windows and Doors Ltd. | Construction | 2019 |
| ALL Around Air Source UK Limited | Construction | 2021 |
| ALL That Counts LLP | | 2018 |
| Allan Webster & SON Ltd | Construction | 2002 |
| Allanwood Press Limited | Manufacturing | 1963 |
| Alpaca Arcade Ltd | Professional & scientific | 2025 |
| Alpha Anodising and Finishing Limited | Wholesale & retail | 2022 |
| Alpha Fire & Air Solutions Limited | Construction | 2016 |
| Alpine Web Solutions Ltd | Information & communication | 2008 |
| Altitude Brand Ltd | Professional & scientific | 2024 |
| Altro Structural Design Ltd | Professional & scientific | 2021 |
| Alwaysshaw.Co.Uk Limited | Arts & recreation | 2019 |
| AM Civil Consultancy Ltd | Construction | 2026 |
| Amadeus Press Limited | Manufacturing | 1988 |
| Amairah Restaurant Ltd | Hospitality | 2026 |
| Amairah Restaurant Ltd Ltd | Hospitality | 2026 |
| Amanda Ruth Interiors Limited | Professional & scientific | 2022 |
| Amberhue Limited | Wholesale & retail | 2015 |
| AMF Recruitment Ltd | Administrative & support | 2016 |
| AMG Retail Consultancy Limited | Professional & scientific | 2024 |
| Amihc Limited | Professional & scientific | 2021 |
| Amizah Group Ltd | Construction | 2019 |
| Amno Properties Limited | Real estate | 2025 |
| AMW ENG Services Ltd | Professional & scientific | 2020 |
| Andrews Heart & Home Ltd | Real estate | 2024 |
| Angels Tyres Ltd | Wholesale & retail | 2025 |
| Angus Heron Ltd. | Construction | 1988 |
| Angus Testing Services Limited | Professional & scientific | 2014 |
| Animal Trax Academy Ltd | Other services | 2016 |
| Animal Trax Agriculture Ltd | Other services | 2016 |
| Animal Trax Aviation Ltd | Other services | 2016 |
| Animal Trax Corporate Services Ltd | Other services | 2016 |
| Animal Trax Financial Services Ltd | Other services | 2016 |
| Animal Trax International Holdings Ltd | Other services | 2016 |
| Animal Trax International Ltd | Other services | 2016 |
| Animal Trax Leisure Ltd | Other services | 2016 |
| Animal Trax Natural Resources Ltd | Other services | 2016 |
| Animal Trax Oceanic Ltd | Other services | 2016 |
| Animal Trax Retail & Mail Order Ltd | Other services | 2016 |
| Animal Trax Safari Park + Rescue Centre Ltd | Other services | 2016 |
| Animal Trax Ventures Ltd | Other services | 2016 |
| Ank.Art Ltd | Transport & logistics | 2015 |
| Anna Homes Ltd | Real estate | 2016 |
| Anna Upson Ltd | Real estate | 2023 |
| Annabelle Charles Associates Ltd | Administrative & support | 2015 |
| Ante Consulting Limited | Professional & scientific | 2025 |
| Anthem Consultancy Limited | Professional & scientific | 2018 |
| Anthem Investments Limited | Professional & scientific | 2017 |
| Anthem Property Limited | Real estate | 2023 |
| Anya FS Ltd | Manufacturing | 2023 |
| AO Properties Limited | Real estate | 2016 |
| Apex Taverns Ltd | Hospitality | 2024 |
| APM Developers Limited | Construction | 2019 |
| App Factor Ltd | Information & communication | 2018 |
| App Guardian Ltd | Information & communication | 2024 |
| Appletons Solicitors Ltd | Professional & scientific | 2017 |
| Applianceworks Limited | Administrative & support | 2013 |
| Applications Excellence Limited | Information & communication | 2010 |
| Approved Food Limited | Wholesale & retail | 2009 |
| Appytalk Ltd | Information & communication | 2018 |
| Aquatrust Water and Ventilation (Holdings) Ltd | Professional & scientific | 2020 |
| Aquatrust Water and Ventilation Group Limited | Professional & scientific | 2023 |
| Aquila Powder Coatings Limited | Manufacturing | 2007 |
| ARC Industrial Limited | Professional & scientific | 2026 |
| Arden Care Supplies Limited | Wholesale & retail | 2010 |
| Ardsley Boarding Kennels Limited | Other services | 2010 |
| Ariya Properties Limited | Real estate | 2023 |
| ARL Capital Ltd | Financial services | 2026 |
| Array Global Ltd | Wholesale & retail | 2020 |
| As-Computers Limited | Other services | 2013 |
| Asdent Ltd | Health & social care | 2014 |
| ASH ST Ltd | Real estate | 2025 |
| Askbob Limited | Professional & scientific | 2025 |
| Aspect Performance Limited | Manufacturing | 2023 |
| AST Managed Services Ltd | Wholesale & retail | 2022 |
| Astin Dawson & Family Ltd | Real estate | 2025 |
| Astute Pension Trustees Limited | Financial services | 2013 |
| ATI Green Energy Ltd | Other services | 2016 |
| ATI Property Holdings Ltd | Other services | 2016 |
| Atlas Contracting Group Ltd | Construction | 2026 |
| Atlas Haulage Limited | Wholesale & retail | 2023 |
| Aurum Online Limited | Wholesale & retail | 2014 |
| Aurum Retail Limited | Wholesale & retail | 2021 |
| Aurus Holdings Limited | Financial services | 2024 |
| Autoblast Limited | Manufacturing | 1993 |
| AV4BUSINESS Limited | Transport & logistics | 2000 |
| Avioly Ltd | Wholesale & retail | 2021 |
| AWC Utilities Consulting Limited | Administrative & support | 2025 |
| Azpro Developments Limited | Real estate | 2023 |
| Azuma Holdings Limited | Financial services | 2023 |
| B & W Services Ltd | Transport & logistics | 2019 |
| B a T (2000) Limited | Manufacturing | 2021 |