| ASR Cars Ltd | Administrative & support | 2018 |
| Assa Trade Supply Ltd | Wholesale & retail | 2025 |
| Assal Cars Ltd | Transport & logistics | 2025 |
| Assani Ltd | Real estate | 2020 |
| Assavel Ltd | Professional & scientific | 2024 |
| Assayer Limited | Administrative & support | 2015 |
| Assessify Health Ltd | Information & communication | 2026 |
| Asset Protection Facilities Management Limited | Professional & scientific | 2015 |
| Assia Limited | Real estate | 2007 |
| Assist Bridging Ltd | Financial services | 2022 |
| Associates Enterprise Limited | Administrative & support | 2019 |
| Association of Mongolian Women in the UK Limited | Other services | 2025 |
| Assured Roots CIC | Education | 2025 |
| Assureline Compliance Ltd | Professional & scientific | 2026 |
| Astar Building & Construction Ltd | Construction | 2019 |
| Astara Travels Ltd | Transport & logistics | 2025 |
| Astha Group UK Ltd | Wholesale & retail | 2023 |
| Aston Management Services Limited | Administrative & support | 2011 |
| Astonish Solutions Ltd | Construction | 2020 |
| Astor CON Ltd | Professional & scientific | 2022 |
| Astra UK Retail Ltd | Manufacturing | 2025 |
| Astra Wholesale Ltd | Wholesale & retail | 2023 |
| Astrid Properties Ltd | Construction | 2013 |
| Astryx Limited | Information & communication | 2026 |
| Asudacity Ltd | Information & communication | 2023 |
| Asumah Holding Group Ltd | Financial services | 2025 |
| Asya Technologies Ltd | Information & communication | 2016 |
| ASZ Car Hire Ltd | Transport & logistics | 2023 |
| AT K Global Limited | Health & social care | 2022 |
| AT Khaleel Ltd | Real estate | 2024 |
| ATA Management Limited | Real estate | 2023 |
| Atai Property Holding Limited | Real estate | 2023 |
| Ataman Trading Limited | Information & communication | 1999 |
| Atariya Foods Retail (UK) Limited | Wholesale & retail | 2017 |
| Atco Pharma Ltd | Wholesale & retail | 2024 |
| Atelier Bohemia Limited | Construction | 2025 |
| Atenai London Limited | Wholesale & retail | 2024 |
| Atgshop Ltd | Wholesale & retail | 2025 |
| Athenic Food Limited | Wholesale & retail | 2024 |
| Athens Eyes Limited | Health & social care | 2018 |
| Athleticoapparel Ltd | Manufacturing | 2024 |
| ATL Ocean Limited | Administrative & support | 2021 |
| Atlanta F&B Limited | Hospitality | 2025 |
| Atlanta Investment Group Limited | Hospitality | 2023 |
| Atlantas Bulk Ship Management Ltd. | Administrative & support | 2020 |
| Atlantas Offshore Ship Management Limited | Administrative & support | 2026 |
| Atlantas Ship Group Limited | Administrative & support | 2016 |
| Atlantas Ship Management Limited | Administrative & support | 2014 |
| Atlantas Technical Services Limited | Administrative & support | 2016 |
| Atlantis Management Ltd | Real estate | 2009 |
| Atlas Core Cloud Ltd | Information & communication | 2025 |
| Atlas GAS Services Ltd | Construction | 2023 |
| Atlas Teck Ltd | Wholesale & retail | 2017 |
| Atoken Limited | Information & communication | 2019 |
| Atputha Vinayagar | Other services | 2017 |
| Atrion Ltd | Wholesale & retail | 2026 |
| Atrium Event Solutions Ltd | Administrative & support | 2023 |
| ATS Carpets Ltd | Wholesale & retail | 2015 |
| ATS Premier Services Ltd | Construction | 2024 |
| AU International Ltd | Wholesale & retail | 2020 |
| AU Solutions Ltd | Construction | 2025 |
| Audiology Care Limited | Wholesale & retail | 2020 |
| Auditsail Limited | Information & communication | 2026 |
| August 17 Limited | Professional & scientific | 2006 |
| Augustus Developments Ltd | Real estate | 2025 |
| AUK Group Limited | Real estate | 2022 |
| Auke Limited | Hospitality | 2026 |
| AUM Kitchen Ltd | Manufacturing | 2021 |
| Aung World Ltd | Other services | 2014 |
| Auntie A'S Daycare Limited | Education | 2026 |
| Aunty Jenny’S Food Ltd | Hospitality | 2024 |
| Aunty Madge Caribbean Cuisine Limited | Hospitality | 2017 |
| Aura Bespoke Construction Ltd | Construction | 2020 |
| Aura Beverages Limited | Wholesale & retail | 2024 |
| Auranotes Ltd | Wholesale & retail | 2026 |
| Aurasyia Scop Group Investment UK Ltd | Financial services | 2025 |
| Aurasyia Scop Group OIL & GAS UK Limited | Financial services | 2019 |
| Aurea Star Traders Ltd | Wholesale & retail | 2025 |
| Aurelia Events Limited | Arts & recreation | 2025 |
| Aureva Ritual Ltd | Wholesale & retail | 2026 |
| Aurevion Ltd | Information & communication | 2026 |
| Aurixa Services Limited | Wholesale & retail | 2025 |
| Aurora Star Ltd | Other services | 2025 |
| Aurorium London Limited | Construction | 2024 |
| Authentic Cedar Development Ltd | Construction | 2014 |
| Auto 4U Ltd | Wholesale & retail | 2012 |
| Auto Accident Assist (UK) Limited | Administrative & support | 2003 |
| Auto Assist Claims Ltd | Administrative & support | 2016 |
| Auto Body Zone Limited | Wholesale & retail | 2016 |
| Auto Dubbz Ltd | Wholesale & retail | 2023 |
| Auto Group Customs Ltd | Wholesale & retail | 2024 |
| Auto Group Ltd | Wholesale & retail | 2020 |
| Auto London Ltd | Manufacturing | 2022 |
| Auto Serve Vehicle Solutions Limited | Wholesale & retail | 2011 |
| Auto Tech UK Ltd | Wholesale & retail | 2018 |
| Auto Trans (UK) Limited | Wholesale & retail | 2014 |
| Auto VEK Limited | Wholesale & retail | 2021 |
| Autocare Pro Ltd | Wholesale & retail | 2024 |
| Autokaaran Ltd | Hospitality | 2024 |
| Autolabs Services Limited | Wholesale & retail | 2024 |