| Ares Foreign Trade Ltd | Wholesale & retail | 2019 |
| ARI Drivers Ltd | Transport & logistics | 2008 |
| Aria Education Ltd | Education | 2020 |
| Arian Medical Ltd | Wholesale & retail | 2020 |
| Arian Medical Retail Ltd | Wholesale & retail | 2022 |
| Aristos IT Limited | Information & communication | 2014 |
| Aristos SPV Limited | Real estate | 2026 |
| Ariya Florist Ltd | Wholesale & retail | 2026 |
| Arjai Properties Ltd | Real estate | 2016 |
| Arkle Finance Limited | Financial services | 1997 |
| Arkley Asset Ltd | Financial services | 2023 |
| Arlson Global Limited | Other services | 2018 |
| Armodias Distribution Limited | Wholesale & retail | 2026 |
| Armour Scent Ltd | Wholesale & retail | 2022 |
| Armstrong Plumbing and Heating Services Ltd | Construction | 2014 |
| Arolite Ltd | Professional & scientific | 2009 |
| Aroma Taste Limited | Hospitality | 2020 |
| Aromadrive Ltd | Wholesale & retail | 2025 |
| Aromatan UK Ltd | Wholesale & retail | 2020 |
| Arra Services Limited | Other services | 2023 |
| Arrow Design Services Ltd | Professional & scientific | 2020 |
| Arthur Fitzhugh Decorating Limited | Construction | 2014 |
| Artifact (Weston Favell) Ltd | Arts & recreation | 2018 |
| Artifact Tattoo Ltd | Other services | 2013 |
| Artists for GOD Ltd | Information & communication | 2025 |
| Artizan Construction Ltd | Construction | 2021 |
| Artmat Brickwork and Construction Ltd | Manufacturing | 2024 |
| Artminds Ltd | Education | 2020 |
| Arty Limited | Information & communication | 2024 |
| ARW Management Limited | Professional & scientific | 1998 |
| Aryan International Foods Ltd | Wholesale & retail | 2025 |
| AS Barbers Shop Ltd | Other services | 2024 |
| AS Golden Barbers Ltd | Other services | 2026 |
| Asakyem UK Ltd | Health & social care | 2026 |
| Ascend Pharma Services Ltd | Wholesale & retail | 2025 |
| Ascenda Lifts Ltd | Manufacturing | 2024 |
| Ascent Trinity Limited | Wholesale & retail | 2021 |
| Aseld Limited | Public administration | 2010 |
| ASG Moto Ltd | Wholesale & retail | 2021 |
| ASH Planning Ltd | Professional & scientific | 2020 |
| ASH Services GB Limited | Construction | 2007 |
| Ashanti Services Ltd | Health & social care | 2015 |
| Ashdon Consultants Ltd | Other services | 2020 |
| Ashiana Takeaway Colchester Ltd | Hospitality | 2019 |
| Ashton Pumps Ltd | Wholesale & retail | 2009 |
| ASK Packaging Ltd | Administrative & support | 2018 |
| Aspirational Homes Limited | Real estate | 2018 |
| Aspire Property Renovations Ltd | Construction | 2018 |
| ASR Motor Body Engineering Limited | Manufacturing | 2004 |
| Asset Finance Northampton Limited | Financial services | 2017 |
| Asset Homes Ltd | Real estate | 2023 |
| Assure Safe UK Ltd | Administrative & support | 2025 |
| AST Transporter Ltd | Transport & logistics | 2018 |
| Astera Kitchen Ltd. | Wholesale & retail | 2026 |
| Astraseal (Holdings) Limited | Financial services | 1999 |
| Astraseal Limited | Extraterritorial | 2018 |
| AT My Smile Studio Limited | Health & social care | 2024 |
| AT4 Limited | Professional & scientific | 2024 |
| Athenaeum Proform Ltd | Health & social care | 2025 |
| Athletes Best Source Ltd | Manufacturing | 2023 |
| Athlias Management Ltd | Construction | 2026 |
| Atim Empire Ltd | Construction | 2018 |
| ATL Windows & Home Improvements Limited | Construction | 2013 |
| Atline Services Ltd | Construction | 2015 |
| ATN - ASK the Networks Ltd | Information & communication | 2025 |
| ATO Training Limited | Construction | 2020 |
| Aton Solutions Limited | Administrative & support | 2022 |
| Atosa Catering Equipment UK Ltd | Wholesale & retail | 2012 |
| Attain Financial Solutions Limited | Financial services | 2018 |
| Aubury Tree Services Limited | Administrative & support | 2015 |
| Audacious Jooce Ltd | Wholesale & retail | 2015 |
| August Media Ltd | Information & communication | 2020 |
| AUM Associates LLP | | 2017 |
| AUM Tech Ltd | Information & communication | 2021 |
| Aura Cleaning Group Limited | Administrative & support | 2025 |
| Auravia Ecommerce Ltd | Wholesale & retail | 2025 |
| Aurela Orthodontics Ltd | Health & social care | 2025 |
| Aurelia Transport Ltd | Transport & logistics | 2016 |
| Austintacious Ltd | Other services | 2015 |
| Autism Kids Club Services Ltd | Health & social care | 2025 |
| Auto Prime Recovery Limited | Wholesale & retail | 2025 |
| Auto Spares & Salvage Limited | Water & waste | 2006 |
| Auto Spectrum 2 Ltd | Wholesale & retail | 2023 |
| Autobusu Ltd | Wholesale & retail | 2018 |
| Autoflow Limited | Information & communication | 2000 |
| Autowerx Limited | Wholesale & retail | 2014 |
| AUX Energy Ltd | Wholesale & retail | 2025 |
| AV CON Ltd | Administrative & support | 2026 |
| Avenue Architectural Design Limited | Professional & scientific | 2018 |
| Avenue Group Holdings Limited | Financial services | 2026 |
| AW Corrporation Ltd | Wholesale & retail | 2025 |
| AW Haulage(Uk) Ltd | Transport & logistics | 2018 |
| AW Searches Ltd | Professional & scientific | 2002 |
| Awesome G Assets Ltd | Hospitality | 2019 |
| Awnings Online Ltd | Extraterritorial | 2024 |
| Awtomation Limited | Professional & scientific | 2020 |
| Axell Sportswear Ltd | Wholesale & retail | 2019 |
| Axis Equipment Ltd | Administrative & support | 2010 |
| Axor Limited | Transport & logistics | 2020 |
| Aydin Food Ltd | Hospitality | 2022 |