| ALL Fire Group Holdings Ltd | Extraterritorial | 2026 |
| ALL Precision Engineering Limited | | 1946 |
| ALL Season Trees Limited | Administrative & support | 2025 |
| ALL Seasons Club Owners Associates Limited | Other services | 2009 |
| ALL SET Limited | Construction | 2004 |
| ALL Timber Solutions Limited | Construction | 2015 |
| ALL4FINANCE Ltd | Information & communication | 2026 |
| Allan Peters Building Ltd | Construction | 2022 |
| Allbeck Homes Limited | Real estate | 2012 |
| Allday Health Ltd | Health & social care | 2024 |
| Allen+Thompson Songs Ltd | Information & communication | 2019 |
| Allenheads Limited | Financial services | 2015 |
| Allfine Roofing Ltd | Construction | 2025 |
| Allhurst Services Ltd | Wholesale & retail | 2023 |
| Alliance for Inclusion Ltd | Professional & scientific | 2024 |
| Alligent Biopharm Consulting (Europe) Limited | Professional & scientific | 2016 |
| Allingham Beck Associates Ltd | Manufacturing | 2008 |
| Allium Designer Homes Ltd | Construction | 2016 |
| Allurea Management Ltd | Professional & scientific | 2024 |
| Almeida Solutions Ltd | Professional & scientific | 2026 |
| Almeria Limited | Information & communication | 1997 |
| Almia Limited | Professional & scientific | 2025 |
| Alpha Air Distribution Limited | Construction | 2010 |
| Alpha Foxtrot Solutions Limited | Professional & scientific | 2021 |
| Alpha Welding and Fabrication Ltd | Construction | 2024 |
| Alpha-Omega Auto Specialists Ltd | Wholesale & retail | 2023 |
| Alphahedge Consulting Ltd | Professional & scientific | 2023 |
| Alpine Electrical Solutions Ltd | Construction | 2025 |
| Altas Auto UK Limited | Extraterritorial | 2020 |
| Altered Wings Limited | Other services | 2024 |
| Alterior Living Limited | Professional & scientific | 2022 |
| Altus Property Limited | Real estate | 2019 |
| Altus Technologies Limited | Information & communication | 2011 |
| Alzec Limited | Real estate | 2023 |
| AM Flooring Surrey Limited | Construction | 2014 |
| AM Skin Clinic Ltd | Other services | 2025 |
| Amanda Louise Legal Consultancy Ltd | Professional & scientific | 2026 |
| Amanda Shaw Solicitors Limited | Professional & scientific | 2011 |
| Amanda Shaw Trustees Limited | Professional & scientific | 2024 |
| Amber Contractors (UK) Ltd | Information & communication | 2001 |
| Amber Scaffolding Limited | Construction | 1990 |
| Ambler Consultants Limited | Construction | 2023 |
| AMC Cornerstone Ltd | Professional & scientific | 2018 |
| Amcal Geospatial Limited | Information & communication | 2013 |
| Amcd Property Ltd | Real estate | 2019 |
| Amduriano Ltd | Health & social care | 2021 |
| Amora (Hurst Farm) Limited | Construction | 2024 |
| Amora (SR) Limited | Construction | 2025 |
| Amora (Vicarage Road) Ltd | Construction | 2022 |
| Amora Homes Limited | Construction | 2016 |
| Amora Limited | Construction | 2011 |
| Amorsel Ltd | Education | 2024 |
| AMP Free Houses Limited | Wholesale & retail | 2024 |
| Ampco 159 Limited | Financial services | 2021 |
| Amplaify Innovations Ltd | Information & communication | 2025 |
| Amplify Data Limited | Information & communication | 2017 |
| Amrexa Ltd | Information & communication | 2024 |
| AMS Establishments Ltd | Hospitality | 2023 |
| Amse Electrical Ltd | Construction | 2026 |
| Anagram Systems Limited | Information & communication | 2000 |
| Anatolia UK Distributions Ltd | Other services | 2013 |
| Anaya NF Ltd | Transport & logistics | 2022 |
| Anchor (Ripley) Trading Limited | Hospitality | 2013 |
| Anchorlayer AI Limited | Information & communication | 2024 |
| Ancora Foundations Ltd | Construction | 2022 |
| Andaman Hills Advisory Ltd | Professional & scientific | 2022 |
| Anderson OIL & GAS Services Ltd | Administrative & support | 2012 |
| Andon Developments (Services) Limited | Administrative & support | 2013 |
| Andrews Meadows Consultancy Limited | Professional & scientific | 2024 |
| Andrews Road Management Company Ltd | Households | 2009 |
| Andy Gwynn Electrical Ltd | Construction | 2015 |
| Andy Handyman Horsham Ltd | Other services | 2025 |
| Angad Private Ltd | Wholesale & retail | 2024 |
| Angel Court Petworth Limited | Households | 2016 |
| Angels Lifestyle Services Ltd | Arts & recreation | 2004 |
| Angels Sales & Marketing Limited | Wholesale & retail | 2013 |
| Anglo-Dutch Applied Technologies Ltd | Professional & scientific | 2015 |
| Angood Electrical Limited | Construction | 2022 |
| Anicetus Performance Ltd | Financial services | 2021 |
| Anjels Beauty Ltd | Professional & scientific | 2022 |
| Anjo Delivery Services 1512 Ltd | Transport & logistics | 2025 |
| Ankr Accountancy Limited | Professional & scientific | 2025 |
| Anling’S Kitchen Limited | Hospitality | 2025 |
| Anna Page Ltd | Professional & scientific | 2025 |
| Annapurna Corporation Ltd | Construction | 2021 |
| Annapurna Spice & Grill Ltd | Hospitality | 2025 |
| Annie's Closet Ltd | Wholesale & retail | 2020 |
| Anova ABS Ltd | Professional & scientific | 2013 |
| Anova Cleghorn Limited | Professional & scientific | 2021 |
| Anova Group Limited | Professional & scientific | 2019 |
| ANR Vehicle Transportation Ltd | Transport & logistics | 2022 |
| Ansell Arboriculture Limited | Administrative & support | 2017 |
| Ansell Limited | Real estate | 2024 |
| Anthony James Cars Ltd | Wholesale & retail | 2019 |
| Antiro Media Ltd | Information & communication | 2023 |
| Antithesis UK Limited | Information & communication | 2020 |
| Antron Engineers Supplies Limited | Wholesale & retail | 2016 |
| Anvita International Limited | Professional & scientific | 2012 |
| ANZ Footcare Ltd | Health & social care | 2023 |
| AO Vision Limited | Information & communication | 2013 |