| Arthitaya's Thai Flavours Ltd | Hospitality | 2025 |
| Artin Food Ltd | Hospitality | 2018 |
| Aruneal Ltd | Real estate | 2026 |
| Arven Capital Partners Limited | Financial services | 2018 |
| Arven Finance Limited | Financial services | 2019 |
| Aryan Property Services Limited | Real estate | 2025 |
| Arzum 02 Limited | Other services | 2020 |
| ASF Civils Ltd | Construction | 2023 |
| Ashbourne Willows Ltd | Real estate | 2020 |
| Ashcrest Joinery Ltd | Construction | 2017 |
| Ashraya Estates Ltd | Real estate | 2025 |
| Asian Fusion Northcamp Ltd | Hospitality | 2026 |
| ASK Tile Agency Limited | Administrative & support | 2023 |
| Assassin Tackle Ltd | Wholesale & retail | 2017 |
| Assen 1 Solution Ltd | Construction | 2019 |
| Asset Communications Ltd | Administrative & support | 2010 |
| Assetvalue Limited | Real estate | 1993 |
| Association of Convenience Stores Limited | Other services | 2000 |
| Assouline UK Limited | Wholesale & retail | 2013 |
| Astrajet Aviation Ltd | Transport & logistics | 2026 |
| Astrajet Ltd | Transport & logistics | 2023 |
| Asvr Holdings Ltd | Real estate | 2025 |
| Atanas Ivanov Zlatkov Ltd | Extraterritorial | 2024 |
| Athene Systems Limited | Information & communication | 1996 |
| Atlas Aerospace Ltd. | Manufacturing | 2018 |
| Atlas Removals Limited | Transport & logistics | 2022 |
| Atlas: Rigging & Action Design Ltd | Arts & recreation | 2021 |
| Atmosan Limited | Other services | 2020 |
| Atom Arthaus Ltd | Administrative & support | 2024 |
| Atom Care Ltd | Information & communication | 2025 |
| Atom Dudden Hill Ltd | Professional & scientific | 2024 |
| Atom Fire Safety Ltd | Professional & scientific | 2024 |
| Atom Maintenance Service Ltd | Construction | 2024 |
| Atom Management Services Limited | Administrative & support | 2023 |
| Atom Monohaus Ltd | Administrative & support | 2024 |
| Atom Operations Ltd | Administrative & support | 2024 |
| Atom Parkhaus Ltd | Other services | 2024 |
| Atom Property AID Ltd | Information & communication | 2024 |
| Atom Warehaus Ltd | Administrative & support | 2024 |
| Attis Ltd | Wholesale & retail | 2017 |
| Aubrun Limited | Health & social care | 2011 |
| Audio Fraternity Ltd | Manufacturing | 2019 |
| Audio Inventions Limited | Professional & scientific | 2016 |
| Audio Reference (UK) Ltd | Wholesale & retail | 2002 |
| Aujla Business Systems Limited | Information & communication | 1995 |
| AUM Gym Limited | Arts & recreation | 2020 |
| Aura Motor Company Ltd | Wholesale & retail | 2009 |
| Austin Phoenix Limited | Real estate | 2003 |
| Authentic Watch Co LLP | | 2024 |
| Auto Electriz Limited | Wholesale & retail | 2024 |
| Auto Service Centre Aldershot Limited | Wholesale & retail | 2018 |
| Autohub Ltd | Professional & scientific | 2003 |
| Automated Gate Solutions Limited | Construction | 2015 |
| Automation Holdco Limited | Financial services | 2025 |
| Automoco Limited | Wholesale & retail | 2022 |
| Autopot (Global) Limited | Manufacturing | 2005 |
| Autotek Servicing & MOT Limited | Wholesale & retail | 2018 |
| Auxlivia Properties Ltd | Real estate | 2022 |
| AV8 Holdings Limited | Administrative & support | 2025 |
| AV8 London Limited | Transport & logistics | 2025 |
| AVA Projects Ltd | Professional & scientific | 2012 |
| Avent Limited | Extraterritorial | 1936 |
| Avery Court Management Company Limited | Households | 1989 |
| AVG Training Ltd | Professional & scientific | 2011 |
| AVI Roofing Ltd | Construction | 2025 |
| Avi-Spl Limited | Information & communication | 2012 |
| Aviation Global Services Ltd | Transport & logistics | 2011 |
| Aviatrix Accountancy Limited | Professional & scientific | 2022 |
| Avidus JET Management Limited | Transport & logistics | 2016 |
| AW Coaching & Consulting Ltd | Professional & scientific | 2024 |
| Awgg Ltd | Construction | 2004 |
| AWR Electrical Design Services Limited | Administrative & support | 2014 |
| Axelbridge Ltd | Hospitality | 2025 |
| Axiome Consulting Ltd | Professional & scientific | 2019 |
| Axis Mundi Holdings Ltd | Administrative & support | 2015 |
| Axylus Limited | Information & communication | 2013 |
| Aynvos Limited | Financial services | 2025 |
| AZ Kitchen Ltd | Wholesale & retail | 2021 |
| Azatom Limited | Administrative & support | 2015 |
| B & MUK Investments Ltd | Real estate | 2024 |
| B and a Window Cleaning Ltd | Administrative & support | 2026 |
| B&E Maintenance Services Limited | Construction | 2014 |
| B. Strong Wellness Ltd | Health & social care | 2025 |
| B.G.T. Automatics Limited | Manufacturing | 1965 |
| B.T.R.S. Limited | Professional & scientific | 2002 |
| B2L Holdings Ltd | Real estate | 2022 |
| B4-GLOBAL Ltd | Professional & scientific | 2024 |
| B4A Inter Group Ltd | Hospitality | 2016 |
| Babar JAN (UK) Limited | Construction | 2008 |
| Bains Business Holding UK Ltd | Arts & recreation | 2026 |
| Baker Commercial Limited | Real estate | 2002 |
| Bakers Dozen North Camp Ltd | Wholesale & retail | 2024 |
| Balcombe Retreat Management Company Limited | Households | 2025 |
| BAM Group (UK) Limited | Financial services | 1978 |
| BAM Nuttall Limited | Construction | 1935 |
| Bamboo Garden Services Limited | Administrative & support | 2014 |
| BAMBOO42 Ltd | Arts & recreation | 2024 |
| Bantok Limited | Real estate | 2024 |
| Bara Group Ltd | Financial services | 2025 |
| Barabasz Recycling Ltd | Wholesale & retail | 2021 |