| Arslan SRS UK Limited | Administrative & support | 2024 |
| Art B Property Ltd | Real estate | 2020 |
| Art by Thea Emilie Ltd | Wholesale & retail | 2021 |
| Art Studio and Events Ltd | Arts & recreation | 2025 |
| Art-Pol Construction Limited | Construction | 2004 |
| Art-Pol Development Ltd | Real estate | 2019 |
| Art-Pol Joinery Limited | Manufacturing | 2007 |
| Artans Basements & Extensions Ltd | Construction | 2026 |
| Arteum Group Ltd | Arts & recreation | 2023 |
| Arthur LEE & Sons (Hot Rolling Mills) Limited | Extraterritorial | 1948 |
| Artisan Perfection Ltd | Information & communication | 2024 |
| Arto Investments Ltd | Households | 2017 |
| Aruk Group Ltd | Transport & logistics | 2023 |
| ARW Estate Ltd | Real estate | 2024 |
| ARZ Business Solutions Ltd | Professional & scientific | 2025 |
| Arzar Transtech Enterprises Ltd | Wholesale & retail | 2024 |
| AS Autofix Limited | Wholesale & retail | 2023 |
| Asafoods UK Ltd | Wholesale & retail | 2026 |
| Ascend Training Ltd. | Education | 2013 |
| ASF Supplier Ltd | Wholesale & retail | 2026 |
| Asghar Surveys Ltd | Professional & scientific | 2025 |
| ASH Nail & Beauty Ltd | Other services | 2023 |
| Ashanti Driving School Limited | Education | 2012 |
| Ashanti Properties Ltd | Real estate | 2020 |
| Ashbal Services Limited | Transport & logistics | 2014 |
| Ashcroft Commercial Property Limited | Real estate | 2026 |
| Ashiq Studio Limited | Manufacturing | 2017 |
| Ashkira Limited | Real estate | 2025 |
| Ashley Industrial Solutions Ltd | Construction | 2026 |
| Ashve Ltd | Hospitality | 2013 |
| Ashwini Properties Ltd | Real estate | 2013 |
| Asiaw Studio Ltd | Information & communication | 2019 |
| Asif Builders Ltd | Construction | 2021 |
| ASK Law Legals Ltd | Professional & scientific | 2021 |
| Asmar DV Ltd | Construction | 2016 |
| Asmart Design Limited | Professional & scientific | 2025 |
| Aspa Properties Ltd | Real estate | 2021 |
| Aspect Care Services Ltd | Health & social care | 2023 |
| Aspect Realty Limited | Real estate | 2024 |
| Aspire Care Services Ltd | Health & social care | 2016 |
| Aspire Knight Limited | Administrative & support | 2018 |
| Aspire Skincare Limited | Wholesale & retail | 2015 |
| Aspyre Health Care Ltd | Health & social care | 2014 |
| ASR Management Consultants Ltd | Professional & scientific | 2021 |
| Asset Grove Investments Limited | Real estate | 2016 |
| Asset Property & Management Ltd | Construction | 2026 |
| Aster Buildwell Ltd | Real estate | 2022 |
| Aster Desizn Ltd | Real estate | 2023 |
| Asteur Films Ltd | Information & communication | 2014 |
| Astral Ascend Ltd | Financial services | 2026 |
| Astronova Ltd | Administrative & support | 2024 |
| Astrum Wine Cellars Limited | Wholesale & retail | 1997 |
| AT & C Ltd | Construction | 2019 |
| AT Your Help Limited | Health & social care | 2021 |
| At&K Ltd | Wholesale & retail | 2012 |
| ATL ALL Transport London Ltd | Transport & logistics | 2014 |
| Atlass Motors Ltd | Wholesale & retail | 2021 |
| ATN Tech Ltd | Construction | 2025 |
| ATP World Limited | Wholesale & retail | 2016 |
| Atra Foods Ltd | Hospitality | 2025 |
| Atra Ltd | Hospitality | 2016 |
| Atra Properties Ltd | Real estate | 2024 |
| ATS Creative Academy CIC | Information & communication | 2019 |
| Attachment IT Limited | Information & communication | 2024 |
| Attax Accountants Ltd | Professional & scientific | 2020 |
| AU Wholesalers Limited | Wholesale & retail | 2025 |
| Audio Sphere Limited | Information & communication | 2023 |
| Aulakh Movers Ltd | Transport & logistics | 2025 |
| Aurora Wellbeing Limited | Education | 2021 |
| Austin Black Ltd | Real estate | 2026 |
| Australian Card Clothing Limited | Extraterritorial | 1979 |
| Auto Diagnostics Solutions Ltd | Wholesale & retail | 2025 |
| Auto Logic Crawley Ltd | Wholesale & retail | 2025 |
| Auto Logic Gatwick Ltd | Wholesale & retail | 2024 |
| Auto Pickup Ltd | Transport & logistics | 2026 |
| Autoaestheticsuk Ltd | Administrative & support | 2023 |
| Autonomy Health Ltd | Health & social care | 2019 |
| Autopartstrader Limited | Wholesale & retail | 2021 |
| Autotdech Balham Ltd | Wholesale & retail | 2025 |
| Autotech of Wandsworth Ltd | Wholesale & retail | 2010 |
| Autumn Drive Investments Limited | Real estate | 2026 |
| Auzm Ltd | Wholesale & retail | 2024 |
| Avantgarde Renovations Ltd | Construction | 2016 |
| Avanti Mental Well-Being CIC | Education | 2018 |
| Avax Ltd | Construction | 2025 |
| Aventro Labs Ltd | Information & communication | 2026 |
| Avess Ltd | Professional & scientific | 2025 |
| AVG Digital Ltd | Professional & scientific | 2020 |
| Avia Media Ltd | Information & communication | 2024 |
| Aviexpress Ltd | Wholesale & retail | 2020 |
| AVM London Attraction Ltd | Wholesale & retail | 2010 |
| Avoross Ltd | Wholesale & retail | 2011 |
| AVS Electrical Limited | Construction | 2017 |
| AW Elite Properties Limited | Real estate | 2025 |
| AW Estates & Lettings Ltd | Real estate | 2025 |
| Awais Motors Ltd | Wholesale & retail | 2025 |
| Awesome Homeware Limited | Wholesale & retail | 2020 |
| Awesomesource Ltd | Information & communication | 2016 |
| AWK Construction Ltd | Construction | 2020 |
| AWK Rentals Ltd | Real estate | 2025 |