| Astley Cars (NW) Limited | Wholesale & retail | 2015 |
| Astley Gorse Solar Limited | Construction | 2022 |
| Astley Hall Limited | Transport & logistics | 1998 |
| Aston & Global Ltd | Administrative & support | 2014 |
| Aston Point Limited | Construction | 2017 |
| Aston Projects Limited | Hospitality | 2018 |
| Astraea Online Limited | Other services | 2025 |
| Astro Academy Warrington CIC | Education | 2023 |
| Astro Project Control Limited | Professional & scientific | 2020 |
| ASU Holdings Limited | Professional & scientific | 2020 |
| ASU Investments Limited | Real estate | 2024 |
| ASW Integrated Ltd | Construction | 2026 |
| Aswi Recruitment Ltd | Administrative & support | 2017 |
| AT Flooring NW Ltd | Construction | 2025 |
| AT Home Neuro Rehab Limited | Other services | 2019 |
| AT Lettings (Warrington) Limited | Construction | 2021 |
| AT Property and Estates Ltd | Real estate | 2021 |
| AT Retirement Options Wealth Management Ltd | Financial services | 2013 |
| AT Software Consultancy Limited | Information & communication | 2018 |
| Atbol Holdco 123 Limited | Real estate | 2023 |
| ATD Engineering Limited | Professional & scientific | 2023 |
| ATD3D Ltd | Wholesale & retail | 2022 |
| Atdetail Ltd. | Professional & scientific | 2020 |
| ATE Holdings Ltd | Other services | 2023 |
| ATE Hospitality Ltd | Hospitality | 2021 |
| Atelier EC Limited | Administrative & support | 2026 |
| Ateliora Magna Ltd | Wholesale & retail | 2025 |
| Atex Explosion Hazards Limited | Manufacturing | 1973 |
| ATG Airports (Products) Limited | Extraterritorial | 2007 |
| ATG Airports Limited | Manufacturing | 1991 |
| ATG UK Limited | Professional & scientific | 1999 |
| Athelis Financial Ltd | Financial services | 2018 |
| Athena Energy Limited | Information & communication | 2018 |
| Athena IP Holdings Ltd | Professional & scientific | 2026 |
| Athena Projects Plus Ltd | Wholesale & retail | 2010 |
| Athens Value Creation Consultancy Limited | Financial services | 2025 |
| ATI Contracts Ltd | Construction | 2015 |
| ATI Insulation Contractors Limited | Construction | 2009 |
| Atier FHL Ltd | Wholesale & retail | 2025 |
| Atika Group Holdings Ltd | Financial services | 2025 |
| Atika Limited | Other services | 2018 |
| Atika London Limited | Wholesale & retail | 2011 |
| Atino Group Limited | Financial services | 2024 |
| ATK Civil Engineering Ltd | Professional & scientific | 2024 |
| ATK Housing Rentals Limited | Real estate | 2025 |
| Atkinson Services Ltd | Professional & scientific | 2024 |
| Atlantic Technology Solutions Limited | Administrative & support | 2025 |
| Atlas 21 Ltd | Manufacturing | 1958 |
| Atlas Environmental Solutions Limited | Administrative & support | 2011 |
| Atlas Hair and Beauty Agencies Limited | Other services | 2021 |
| Atlas Management Consultancy Services Ltd | Professional & scientific | 2023 |
| Atlas Mortgages Ltd | Financial services | 2006 |
| Atlas Northwest Motors Ltd | Wholesale & retail | 2025 |
| Atlas Parcel Delivery Ltd | Transport & logistics | 2026 |
| Atlas QA Ltd | Administrative & support | 2026 |
| Atlas Warrington Ltd | Hospitality | 2026 |
| Atmos Associates Limited | Administrative & support | 2008 |
| Atmosphere-Warrington Ltd | Education | 2026 |
| Atmospheric Products Limited | Professional & scientific | 1983 |
| Atoam Marc Ltd | Administrative & support | 2023 |
| Atom Freelance Ltd | Professional & scientific | 2023 |
| Atom FX Ltd | Arts & recreation | 2023 |
| Atom Global Ltd | Professional & scientific | 2023 |
| Atom Hub Limited | Professional & scientific | 2023 |
| Atom Umbrella Ltd | Professional & scientific | 2023 |
| Atomic Analysis Ltd | Professional & scientific | 2026 |
| Atomic Digital Marketing Ltd | Information & communication | 2020 |
| Atomic Talent Agency Ltd | Arts & recreation | 2025 |
| Atoz Haulage Ltd | Transport & logistics | 2021 |
| Atpfury Limited | Administrative & support | 2014 |
| Atputas Engineering Ltd | Administrative & support | 2026 |
| Atria Project Solutions Limited | Information & communication | 2016 |
| Atrotor Limited | Professional & scientific | 2018 |
| ATS 100 Consultancy Limited | Administrative & support | 2016 |
| ATS Trans Ltd | Transport & logistics | 2016 |
| Attain HR Solutions Limited | Professional & scientific | 2015 |
| Attitude Mens Hair Academy Limited | Education | 2011 |
| Attiva Property Ltd | Real estate | 2021 |
| Attribute Intelligent Engineering Limited | Administrative & support | 2025 |
| Attwood Engineering Services Ltd. | Professional & scientific | 2016 |
| Atug Properties Ltd | Real estate | 2025 |
| AU + IO Ltd | Professional & scientific | 2023 |
| Auckland & SON Autos & Commercial Limited | Professional & scientific | 2017 |
| Audio Skills Ltd | Information & communication | 2019 |
| Audition London Limited | Wholesale & retail | 2021 |
| Auditvault Limited | Information & communication | 2025 |
| Audrey Tamba Consulting Ltd | Wholesale & retail | 2019 |
| AUF Ltd | Wholesale & retail | 2012 |
| AUF Properties Limited | Financial services | 2012 |
| Augens Limited | Financial services | 2023 |
| Augur Properties Limited | Real estate | 2018 |
| Augustin Borfotina Ltd | Transport & logistics | 2016 |
| AUH Engineering Ltd | Professional & scientific | 2025 |
| AUM PVT Ltd | Information & communication | 2020 |
| Aura Zero Ltd. | Financial services | 2017 |
| Aurora Consultancy Services Limited | Information & communication | 2023 |
| Aurora Flow AI Ltd | Transport & logistics | 2025 |
| Aurore Caron Engineering Ltd | Professional & scientific | 2023 |
| Austin Civils Limited | Administrative & support | 2025 |
| Austin Fraser International Limited | Administrative & support | 2023 |