| Atlas Corporate Services Ltd | Administrative & support | 2025 |
| Atlas Motor Services Limited | Wholesale & retail | 2005 |
| Atlas Reach Marketing Ltd | Wholesale & retail | 2025 |
| Atlas Utilities Ltd | Construction | 2020 |
| Atme Limited | Administrative & support | 2009 |
| ATN Bakery Ltd | Manufacturing | 2026 |
| ATN Electrical Limited | Construction | 2019 |
| ATN Wholesale Ltd | Manufacturing | 2026 |
| Atom Valley Energy Partnership Ltd | Professional & scientific | 2023 |
| Atomeca Deansgate Square Ltd | Hospitality | 2021 |
| Atomeca Group Ltd | Financial services | 2020 |
| Atomeca Spinningfields Ltd | Hospitality | 2023 |
| Atrium Abodes Ltd | Real estate | 2024 |
| Atsports Coaching Limited | Education | 2022 |
| Attach-Manchester Limited | Health & social care | 2022 |
| Attarka Limited | Construction | 2022 |
| Attingham Partners Limited | Professional & scientific | 2026 |
| Attire Clothing (Holdings) Limited | Professional & scientific | 2016 |
| Attire Clothing Limited | Wholesale & retail | 1999 |
| Atto Digital Limited | Information & communication | 2022 |
| Attor UK Limited | Professional & scientific | 2015 |
| AU Bros Ltd | Wholesale & retail | 2025 |
| AU Construction Management Limited | Construction | 2017 |
| AU Group Ltd | Wholesale & retail | 2025 |
| Aubruley Veterinary Behaviour Referrals Ltd | Professional & scientific | 2026 |
| Auchan Corporation Ltd | Health & social care | 2014 |
| Aucoda Limited | Information & communication | 2018 |
| Auction OMS Limited | Wholesale & retail | 2016 |
| Auctionesm Limited | Households | 2024 |
| Audiam Consult Limited | Professional & scientific | 2020 |
| Audidoctor Ltd | Wholesale & retail | 2019 |
| Audio Broadcast Solutions Ltd | Information & communication | 2020 |
| Audio Enterprise Limited | Arts & recreation | 2018 |
| Audio Video Forensics Limited | Information & communication | 2008 |
| Audio Visual Interactive Technology Limited | Information & communication | 2016 |
| Audio Visual Media Ltd | Information & communication | 2019 |
| Audire Collective Ltd | Health & social care | 2024 |
| Audit & Consult Ltd | Extraterritorial | 2013 |
| Audley Mills EYE Services Limited | Health & social care | 2008 |
| Augtech Global Ltd | Wholesale & retail | 2024 |
| August Thai Limited | Hospitality | 2025 |
| Aulolaland Limited | Real estate | 2019 |
| Aunty Rannys Ltd | Hospitality | 2026 |
| Aunty Sybil's Ltd | Manufacturing | 2024 |
| Aura Home Furnishings Limited | Wholesale & retail | 2013 |
| Aura Luxury Scenting Limited | Wholesale & retail | 2023 |
| Aurabella Living Ltd | Other services | 2025 |
| Auraled Ltd | Wholesale & retail | 2011 |
| Auranic Limited | Wholesale & retail | 2012 |
| Aurea Collections Limited | Wholesale & retail | 2026 |
| Aurestead VI Investments Limited | Real estate | 2025 |
| Auriga Consultants Ltd | Professional & scientific | 2020 |
| Auriga Land and Development Limited | Construction | 2018 |
| Aurora Hills Ltd | Wholesale & retail | 2023 |
| Aurora Lifts Rise With Confidence Limited | Construction | 2025 |
| Aurora Rising Developments Ltd | Real estate | 2020 |
| Aurora Rising Holdings Ltd | Real estate | 2020 |
| Ausavi Ltd | Administrative & support | 2010 |
| Austin Court Residents Association Limited | Households | 1971 |
| Austin Siviour Limited | Professional & scientific | 2024 |
| Australian Academy of Reformer Pilates UK Ltd | Education | 2025 |
| Autista Lang Ltd | Wholesale & retail | 2025 |
| Auto Accumulators Ltd | Wholesale & retail | 2022 |
| Auto AID Windscreens Limited | Wholesale & retail | 2004 |
| Auto Cleanze Ltd | Administrative & support | 2024 |
| Auto Corner Limited | Wholesale & retail | 2024 |
| Auto Custom Kitchen Ltd | Wholesale & retail | 2024 |
| Auto Exchange Ltd | Administrative & support | 2016 |
| Auto Finance Technology Ltd | Administrative & support | 2023 |
| Auto Guide Limited | Wholesale & retail | 2021 |
| Auto Keys 247 Ltd | Professional & scientific | 2023 |
| Auto Legal Direct Limited | Wholesale & retail | 2002 |
| Auto Parts Express Ltd | Wholesale & retail | 2018 |
| Auto Plant Repair Services Ltd | Wholesale & retail | 2014 |
| Auto Point Stockport Ltd | Wholesale & retail | 2019 |
| Auto Rental Sweden Ltd | Administrative & support | 2015 |
| Auto Repair Centre MCR Ltd | Wholesale & retail | 2024 |
| Auto Van Hire Limited | Administrative & support | 2024 |
| Autobody-Uk Ltd | Wholesale & retail | 2025 |
| Autobox Limited | Administrative & support | 2012 |
| Autobrite Direct Limited | Wholesale & retail | 2012 |
| Autofast TEC Limited | Wholesale & retail | 2000 |
| Autogem Fleet Solutions Group Limited | Transport & logistics | 2026 |
| Autogem Fleet Solutions Ltd | Transport & logistics | 2025 |
| Autohub Northwest Ltd | Wholesale & retail | 2018 |
| Autoklinikk Ltd | Administrative & support | 2009 |
| Automate With James Ltd | Information & communication | 2019 |
| Automated Entrances Limited | Administrative & support | 2014 |
| Automated Laundry Equipment Limited | Administrative & support | 2021 |
| Automatica Integrations Ltd | Information & communication | 2026 |
| Automatica Intelligence Ltd | Professional & scientific | 2026 |
| Automation ID Ltd | Information & communication | 2020 |
| Automedi Limited | Manufacturing | 2014 |
| Automotive Carpets Limited | Wholesale & retail | 1992 |
| Automotive Leadership Network Limited | Other services | 2024 |
| Autonomous Vehicle Logistics Ltd | Transport & logistics | 2025 |
| Autostrada Logistics Limited | Transport & logistics | 2020 |
| Autotech Cheshire Limited | Wholesale & retail | 2015 |
| Autotune Limited | Real estate | 1958 |
| Auxano Technologies Limited | Manufacturing | 2009 |