| Aspiring Futures C.I.C. | Education | 2010 |
| Aspro Bookkeeping Limited | Professional & scientific | 2015 |
| ASQ Estates Limited | Real estate | 2024 |
| Asra Digitals Ltd | Information & communication | 2025 |
| Asrtechtools Ltd | Wholesale & retail | 2025 |
| Asset Protection Properties Ltd | Real estate | 2021 |
| Assetflow Property Management Ltd | Real estate | 2024 |
| Assett Property Maintenance Limited | Construction | 2019 |
| Associated Control Systems Limited | Manufacturing | 1998 |
| Associated General Supplies Limited | Wholesale & retail | 2012 |
| Assure Solutions Ltd | Administrative & support | 2020 |
| Assured Vehicle Group Ltd. | Wholesale & retail | 2026 |
| Assurvey Limited | Professional & scientific | 2014 |
| AST Delivery Ltd | Transport & logistics | 2023 |
| AST Psychotherapy Ltd | Health & social care | 2022 |
| Aster Realty Limited | Real estate | 2022 |
| Astera Market Ltd | Wholesale & retail | 2022 |
| Astg Limited | Transport & logistics | 2023 |
| Astion Group Ltd | Professional & scientific | 2026 |
| Astm WM Ltd | Transport & logistics | 2010 |
| Aston Bond Property Ltd | Real estate | 2019 |
| Aston Hall (Garages & Transport) Limited | Wholesale & retail | 1985 |
| Aston Industrial Roofing (Walsall) Limited | Construction | 2004 |
| Aston Safety Signs Limited | Other services | 2011 |
| Aston Transitional Care Limited | Health & social care | 2014 |
| Aston Transport (Midlands) Ltd | Transport & logistics | 2025 |
| Astons of Coven Limited | Wholesale & retail | 2012 |
| Astraeus Limited | Wholesale & retail | 2021 |
| Astraeus Watches Limited | Wholesale & retail | 2015 |
| Astral Sheet Metal (Birmingham) Limited | Real estate | 1976 |
| Astute Financial Planning Limited | Financial services | 2024 |
| Asunik Care Services Ltd. | Administrative & support | 2014 |
| ASW Lettings Limited | Real estate | 2019 |
| ASW Property Limited | Real estate | 2018 |
| ASW Software Ltd | Information & communication | 2015 |
| Asylum Artist Quarter CIC | Arts & recreation | 2019 |
| AT Brothers Ltd | Transport & logistics | 2019 |
| AT Digitizing Ltd | Wholesale & retail | 2024 |
| AT Enterprises Limited | Real estate | 2024 |
| AT EVE Consulting Limited | Professional & scientific | 2014 |
| AT Home Stays Ltd | Real estate | 2025 |
| AT the Foot of the Tree Reflexology Limited | Health & social care | 2023 |
| AT Wholesale Limited | Wholesale & retail | 2023 |
| AT Your Assistance Ltd | Professional & scientific | 2019 |
| At&Ht Ltd | Construction | 2016 |
| ATA Foundation Limited | Other services | 2011 |
| ATA Software Solutions Ltd | Information & communication | 2017 |
| ATA Studios Ltd | Information & communication | 2007 |
| Ataman Ltd | Wholesale & retail | 2016 |
| Atcouriersuk Ltd | Transport & logistics | 2021 |
| Atec Security Limited | Information & communication | 1985 |
| Atec Security Products Limited | Professional & scientific | 2017 |
| Atees Europe (U.K) Ltd | Information & communication | 2023 |
| Atelier Aesthetics Limited | Health & social care | 2025 |
| Atelier DEL Cibo Ltd | Hospitality | 2023 |
| Atelier Gourmand by OC Ltd | Manufacturing | 2025 |
| ATF Electrics Ltd | Construction | 2026 |
| Atfil Limited | Administrative & support | 2019 |
| ATG Estates Limited | Real estate | 2018 |
| ATH RAD Ltd | Health & social care | 2026 |
| Athena Evolve Ltd | Administrative & support | 2020 |
| Athenian Express Ltd | Hospitality | 2025 |
| Atherstone Accident Repair Centre Limited | Wholesale & retail | 1998 |
| Athletape Ltd | Wholesale & retail | 2023 |
| Athletic Body Ltd | Wholesale & retail | 2011 |
| Athlone Road Property Management Limited | Professional & scientific | 2026 |
| Athwal Holdings Limited | Financial services | 2008 |
| Athwal Property Ventures Limited | Real estate | 2021 |
| Athwalsubs Ltd | Hospitality | 2024 |
| ATK PVT Ltd | Wholesale & retail | 2026 |
| Atkale Transport Ltd | Transport & logistics | 2025 |
| Atkin & Evans Limited | | 1965 |
| Atkins Promotions Limited | Arts & recreation | 2012 |
| Atlanta Kilts Ltd | Wholesale & retail | 2026 |
| Atlas Classical Easyward Ltd | Professional & scientific | 2026 |
| Atlas Echo Limited | Transport & logistics | 2025 |
| Atlas K9 Limited | Administrative & support | 2018 |
| Atlas Learning Holdings Limited | Manufacturing | 2026 |
| Atlas Property Services UK Limited | Construction | 2007 |
| ATM 1 Limited | Hospitality | 2025 |
| Atmos Tech AI Ltd | Information & communication | 2026 |
| Atom Carpentry & Construction Limited | Construction | 2017 |
| Atom Glass Projects Limited | Construction | 2025 |
| Atrek Ltd | Arts & recreation | 2025 |
| Atss Trading Ltd | Wholesale & retail | 2021 |
| Attim Services Limited | Administrative & support | 2017 |
| Attock Taxis Limited | Transport & logistics | 2012 |
| Attrayants Ltd | Transport & logistics | 2019 |
| Atwal Property Group Limited | Financial services | 2018 |
| Atwal Transport Limited | Transport & logistics | 2022 |
| Atwell Properties Services Limited | Construction | 2015 |
| Atwoz Media House Ltd | Information & communication | 2026 |
| AU Design Ltd | Manufacturing | 2016 |
| Auctus BID Consulting Ltd | Administrative & support | 2014 |
| AUD Traders Limited | Wholesale & retail | 2026 |
| Audacious Investments Limited | Real estate | 2020 |
| Audit My Freight Ltd | Transport & logistics | 2017 |
| Audota Ltd | Construction | 2021 |
| Augimono Ltd. | Administrative & support | 2016 |
| Augira Ltd | Wholesale & retail | 2013 |