| Atwood Property Management Limited | Households | 2013 |
| ATX Holdings Ltd | Information & communication | 2026 |
| ATY 007 Ltd | Health & social care | 2017 |
| Atyaf Al-Numo Ltd | Wholesale & retail | 2026 |
| Atyd Property Ltd | Real estate | 2025 |
| Atyk Limited | Construction | 2025 |
| Atzaro Box Clever Limited | Construction | 2020 |
| Atzaro Consulting Limited | Construction | 2019 |
| Atzaro Developments Limited | Construction | 2019 |
| Atzaro Property Limited | Construction | 2019 |
| Atzaro Real Estate Limited | Construction | 2013 |
| AU Fait Health Care Consulting Ltd | Professional & scientific | 2022 |
| AU Goldsmith Ltd | Manufacturing | 2025 |
| AU Hulage (NW) Ltd | Transport & logistics | 2025 |
| AU Logistics Limited | Transport & logistics | 2024 |
| AU Wealth Management Ltd | Financial services | 2019 |
| AUA Group Limited | Health & social care | 2026 |
| AUA Trading Ltd | Wholesale & retail | 2016 |
| Aubifashions Ltd | Other services | 2021 |
| Aubrey Fragrance Ltd | Manufacturing | 2025 |
| Aubrey Isaacson Solicitors LLP | | 2013 |
| Aubrey LEE Homes Limited | Real estate | 2011 |
| Auburn Innovation Ltd | Wholesale & retail | 2017 |
| Auckland Transport Ltd | Transport & logistics | 2023 |
| Aucteris Limited | Financial services | 2025 |
| Auction Haven Ltd | Wholesale & retail | 2024 |
| Auction Price Industrial Ltd | Wholesale & retail | 2019 |
| Auctionlegals Limited | Professional & scientific | 2025 |
| Auctoritas Advisory Ltd | Professional & scientific | 2026 |
| Auctus Limited | Professional & scientific | 1997 |
| Audacious Foundation | Real estate | 2016 |
| Audacious Properties Ltd | Construction | 2026 |
| Audan Investments Ltd | Real estate | 2016 |
| Audco Limited | Professional & scientific | 1936 |
| Audenshaw Healthcare Ltd | Health & social care | 2024 |
| Audenshaw Motor Company Limited | Wholesale & retail | 2018 |
| Audenshaw Pharmacy Limited | Wholesale & retail | 2004 |
| Audenshaw School Academy Trust | Financial services | 2010 |
| Audeo Fortis Limited | Professional & scientific | 2014 |
| Auderia Ltd | Wholesale & retail | 2025 |
| Audex Holdings Limited | Real estate | 1944 |
| Audhd Space Ltd | Professional & scientific | 2025 |
| Audience Experts Ltd | Professional & scientific | 2023 |
| Audile Limited | Administrative & support | 2003 |
| Audio Bleach Global Ltd | Information & communication | 2025 |
| Audio Exports Limited | Wholesale & retail | 2023 |
| Audio Finance Limited | Professional & scientific | 2020 |
| Audio Industry Ltd | Wholesale & retail | 2021 |
| Audiodsp Limited | Information & communication | 2019 |
| Audiologics & Co UK Ltd | Professional & scientific | 2026 |
| Audiospillage Ltd | Information & communication | 2023 |
| Audiowellness Ltd | Administrative & support | 2024 |
| Audley Properties Ltd | Real estate | 2016 |
| Audra Limited | Real estate | 2012 |
| Audrey's Salon Ltd | Other services | 2025 |
| AUF Collection Ltd | Wholesale & retail | 2024 |
| AUF Creations Ltd | Wholesale & retail | 2025 |
| AUG Group Limited | Real estate | 2021 |
| Aughton Ainsworth International Foundation | Public administration | 2006 |
| Aughton Limited | Construction | 2012 |
| Augment Group Limited | Professional & scientific | 2025 |
| AUGMENT101 Ltd | Information & communication | 2024 |
| Augmenta Consultancy Limited | Information & communication | 2026 |
| Augmented Consulting Ltd | Information & communication | 2022 |
| Augmented Healthcare Ltd | Information & communication | 2025 |
| August 24/7 Care Ltd | Health & social care | 2024 |
| August Consulting Group Ltd | Other services | 2021 |
| Augusta Kenneth Global Ltd | Professional & scientific | 2022 |
| Augusta PUB Company Limited | Hospitality | 2013 |
| Augusta Tech Ltd | Information & communication | 2024 |
| Augustine Logistics Ltd | Transport & logistics | 2022 |
| AUH Holdings Ltd | Real estate | 2026 |
| Auhello Ltd | Professional & scientific | 2026 |
| AUI Consultancy Ltd | Health & social care | 2026 |
| AUK FM Ltd | Administrative & support | 2014 |
| Aulakh Estates Ltd | Real estate | 2024 |
| Aulakh Logistics Ltd | Transport & logistics | 2023 |
| Auld Reekie (HK) Limited | Real estate | 2023 |
| Aulola(Uk) Ltd | Wholesale & retail | 2013 |
| AUM 4U Ltd | Wholesale & retail | 2021 |
| AUM OIL Emporium Limited | Wholesale & retail | 2025 |
| Aumbow Global Link Ltd | Transport & logistics | 2019 |
| Aumbow UK Global Link Ltd | Transport & logistics | 2019 |
| Aumora Ltd | Wholesale & retail | 2023 |
| Aunex Global Limited | Professional & scientific | 2026 |
| Aunt Tilly's Limited | Hospitality | 2015 |
| Auntie | Education | 2009 |
| Auntie Tracey Housekeeping Limited | Other services | 2014 |
| Aunty Chani's Playgroup Ltd | Health & social care | 2026 |
| Aunty Rugs Business Enterprise Ltd | Wholesale & retail | 2019 |
| Auntydaren.Uk Ltd | Information & communication | 2025 |
| Aupex Ltd | Wholesale & retail | 2024 |
| AUR Solutions SP Limited | Information & communication | 2025 |
| AUR Traders Ltd | Wholesale & retail | 2022 |
| Aura Acai Ltd | Hospitality | 2025 |
| Aura Alcove Design Ltd | Wholesale & retail | 2022 |
| Aura and Ayla Limited | Professional & scientific | 2024 |
| Aura Boutique Fitness Limited | Arts & recreation | 2025 |
| Aura by Precious Ltd | Wholesale & retail | 2024 |
| Aura Conservation Limited | Administrative & support | 2006 |