| Ahlan London Limited | Arts & recreation | 2026 |
| AI Digital Consulting Limited | Professional & scientific | 2021 |
| AI Integrate Ltd | Information & communication | 2024 |
| Airsocket Limited | Wholesale & retail | 2006 |
| Airzair Property Investment Company Limited | Real estate | 2026 |
| AJH Projects Ltd | Professional & scientific | 2026 |
| AJK Builders and Property Maintenance Limited | Construction | 2012 |
| AJK Energy Ltd | Construction | 2018 |
| AJP Benning Estates Limited | Real estate | 2021 |
| AJP Benning Group Limited | Financial services | 2022 |
| AJS Building & Maintenance Ltd | Administrative & support | 2016 |
| AJT South East Ltd | Construction | 2022 |
| AK Supported Housing Limited | Health & social care | 2006 |
| Akrivia Supply Chain Ltd | Professional & scientific | 2018 |
| AL UK Fitness Ltd | Arts & recreation | 2025 |
| Alaias House Ltd | Hospitality | 2025 |
| Alan Bond Supplies Ltd | Wholesale & retail | 2020 |
| Albjam Services Ltd | Real estate | 2017 |
| Alcan Construction Ltd | Construction | 2009 |
| Alchemy Flame Retardants Limited | Administrative & support | 2025 |
| Alcor Technologies Limited | Wholesale & retail | 2007 |
| Alex London Limited | Construction | 2004 |
| Alfa Asset Solutions Ltd | Professional & scientific | 2025 |
| Algra Clinical Services Limited | Health & social care | 2025 |
| Algra Property Solutions Limited | Real estate | 2025 |
| ALL 4 Tiling JB Ltd | Construction | 2016 |
| ALL Around Property Maintenance Limited | Administrative & support | 2007 |
| ALL Living Properties Limited | Real estate | 2025 |
| ALL on ME Ltd | Arts & recreation | 2022 |
| ALL Renewables Britain Limited | Manufacturing | 2022 |
| Allfloors Contracts Ltd | Construction | 2005 |
| Alliance Electrical (London) Ltd | Construction | 2019 |
| Almads Holdings Limited | Professional & scientific | 2002 |
| Alokin Ltd | Construction | 2023 |
| Alpha (Overseas) Limited | Transport & logistics | 1996 |
| Alpha Forwarding Limited | Transport & logistics | 2011 |
| Alternative Energy Services Ltd | Professional & scientific | 2019 |
| Alvm UK Limited | Information & communication | 2022 |
| Alymos Limited | Other services | 1978 |
| AM FX Ltd | Administrative & support | 2026 |
| Amber Architectural Ltd | Professional & scientific | 2025 |
| AML Business Change Ltd | Information & communication | 2025 |
| AMP PMS Group Ltd | Construction | 2023 |
| Amrose Evexa Properties Limited | Real estate | 2020 |
| Amrose Property Limited | Real estate | 2020 |
| Ananda Ventures Ltd | Real estate | 2016 |
| Anastasia Coles Ltd | Health & social care | 2026 |
| Anderson Quantrend Limited | Financial services | 1995 |
| Andy Manston Entertainment Ltd | Arts & recreation | 2024 |
| ANG Impex Ltd | Wholesale & retail | 2025 |
| Angel Health & Wellbeing Ltd | Wholesale & retail | 2017 |
| Angle Paving Limited | Construction | 2025 |
| Anglo Caledonia Company Limited | Transport & logistics | 2025 |
| Anita Seth Limited | Professional & scientific | 2017 |
| Anla Healthcare Limited | Health & social care | 2017 |
| Antique Reclaimed Floors Ltd | Construction | 2026 |
| Anton DEK Construction Ltd | Construction | 2025 |
| AO Realtech Ltd | Wholesale & retail | 2025 |
| AOA Liquor Ltd | Wholesale & retail | 2023 |
| AOM Consulting Ltd | Professional & scientific | 2020 |
| AP Consulting and Advisory Ltd | Professional & scientific | 2022 |
| Apatite Service Solutions Ltd | Manufacturing | 2022 |
| Apex Construction Essex Ltd | Construction | 2022 |
| Apex Essentials Ltd | Wholesale & retail | 2024 |
| Apex Payroll Services Ltd | Professional & scientific | 2023 |
| Apollo Roofing Ltd | Construction | 2018 |
| Apps Delivery Ltd | Information & communication | 2014 |
| Aquarend Contracting Limited | Construction | 1991 |
| Aquarend Holdings Limited | Administrative & support | 1982 |
| Aquarend Limited | Construction | 1990 |
| Aquarend Properties Limited | Real estate | 2019 |
| Aquarend Specialist Works Limited | Administrative & support | 2014 |
| Aquarend Waterproofing Limited | Administrative & support | 2014 |
| Aquarius Heating and Plumbing Ltd | Construction | 2022 |
| Aquatic Excellence Limited | Agriculture & fishing | 2020 |
| AR East Consulting Ltd | Professional & scientific | 2025 |
| Aran Scientific Communications Ltd | Professional & scientific | 2022 |
| Arastrum Ltd | Other services | 2018 |
| Archduke Limited | Information & communication | 2022 |
| Archmark Abodes Limited | Real estate | 2025 |
| Archmark Construction Ltd | Construction | 2021 |
| Arcus FM Limited | Real estate | 2008 |
| Arcus Managed Services Limited | Manufacturing | 2009 |
| Arcus Solutions (Holdings) Limited | Professional & scientific | 2010 |
| Ardan Developments Ltd | Construction | 2013 |
| Ardan Properties Limited | Real estate | 2024 |
| Areta Consulting Ltd | Professional & scientific | 2025 |
| ARG Interior Limited | Construction | 2008 |
| Arkem Finance Ltd | Professional & scientific | 2019 |
| Arkem Ltd | Information & communication | 2012 |
| Arrazzaq Trading Limited | Wholesale & retail | 2019 |
| Art of Scaffolding Ltd | Construction | 2019 |
| Artemis Interior Design Limited | Professional & scientific | 2017 |
| Artgo Limited | Transport & logistics | 2018 |
| Arundel Barnett Company Ltd | Professional & scientific | 2023 |
| AS Transportation Services Limited | Transport & logistics | 2025 |
| ASC Site Services Ltd | Construction | 2022 |
| Ascend Drone Service Limited | Information & communication | 2021 |
| Ashford Hale Limited | Construction | 2024 |
| Ashitaka Services Limited | Professional & scientific | 2015 |