| ALL Over London Scaffolding Ltd | Construction | 2015 |
| ALL Over Roofing & Building Services Limited | Construction | 2026 |
| ALL Over Surrey Limited | Construction | 2025 |
| ALL Saints Court (Bristol 2) Management Company Limited | Households | 2022 |
| ALL Things Identity Limited | Information & communication | 2023 |
| ALL Type Roofers Limited | Construction | 2025 |
| Allan Counselling and Consulting Ltd | Health & social care | 2025 |
| Allan Family Limited | Financial services | 2025 |
| Allema Ltd | Administrative & support | 2013 |
| Allen Pro Build Rentals Ltd | Administrative & support | 2025 |
| Alley Way Barbers Ltd | Other services | 2018 |
| Allgas UK Ltd | Construction | 2003 |
| Allied Systems Ltd | Financial services | 2005 |
| Allpawsondeck Ltd | Wholesale & retail | 2025 |
| Allpro Roofing&Guttering Ltd | Construction | 2023 |
| Allstaroutlet Ltd | Wholesale & retail | 2020 |
| Alltype Plumbing & Heating Ltd | Construction | 2009 |
| Allure Jewellers Ltd | Manufacturing | 2019 |
| Allvia Limited | Wholesale & retail | 2026 |
| Alma Smiles Limited | Health & social care | 2026 |
| ALMA33 Limited | Professional & scientific | 2010 |
| Alpacka Tech Limited | Administrative & support | 2023 |
| Alpha (Cheam) Limited | Construction | 2018 |
| Alpha Car Parts Ltd | Wholesale & retail | 2021 |
| Alpha Day (UK) Limited | Education | 2001 |
| Alpha Development Consultants Ltd | Construction | 2023 |
| Alpha Lark Consulting Limited | Professional & scientific | 2020 |
| Alpha Security UK Ltd. | Administrative & support | 2011 |
| Alphacells Biotechnologies Limited | Manufacturing | 2019 |
| Alphas Services Ltd | Information & communication | 2026 |
| Alpheratz Consulting Ltd | Information & communication | 2020 |
| Alpine Advantage Limited | Professional & scientific | 2009 |
| Alpine Executive Limited | Administrative & support | 2009 |
| Alpine Interim Limited | Administrative & support | 2009 |
| Alpine Investments 2010 Limited | Administrative & support | 2010 |
| Alpine Resourcing Limited | Professional & scientific | 2003 |
| Alrich UK Consulting Services Ltd. | Information & communication | 2014 |
| Alsahafcare.Com Limited | Health & social care | 2010 |
| Altas Landscape Solutions Ltd | Administrative & support | 2023 |
| Alter Assets Ltd | Real estate | 2025 |
| Alter Motion Creative Ltd | Information & communication | 2021 |
| Alternative Learning Trust | Education | 2019 |
| Alternative Sussex Weddings Ltd | Arts & recreation | 2025 |
| Altham Lewis Architects Limited | Professional & scientific | 2013 |
| Alui Holdings Limited | Information & communication | 2021 |
| Alui Limited | Information & communication | 2007 |
| Alui Support Limited | Information & communication | 2021 |
| Alvernia Lodge RTM Company Limited | Households | 2012 |
| Always Brit Ltd | Extraterritorial | 2025 |
| Alyana Tech Limited | Wholesale & retail | 2025 |
| AM Alliance Ltd | Wholesale & retail | 2020 |
| AMA Building Ltd | Construction | 2019 |
| Amanaah Remit Ltd | Financial services | 2026 |
| Amaris Group Media Ltd | Arts & recreation | 2025 |
| Amauzari Progress Union International Limited | Education | 2025 |
| Amayo Limited | Professional & scientific | 2018 |
| Amazing Life Holdings Ltd | Professional & scientific | 2013 |
| Amazingblinds Ltd | Other services | 2026 |
| Amazonas Limited | Wholesale & retail | 2025 |
| AMB Builders Ltd | Construction | 2015 |
| Amba Limited | Real estate | 1983 |
| Amber + Grey Surrey Ltd | Wholesale & retail | 2020 |
| Amber Accident Solutions Limited | Administrative & support | 2022 |
| Amber Business Group Ltd | Financial services | 2023 |
| Amber Coast Ltd | Administrative & support | 2011 |
| Amber Foods (Trading) Ltd | Wholesale & retail | 2020 |
| Amber Global Ltd | Wholesale & retail | 2019 |
| Amber Mercy Ltd | Wholesale & retail | 2026 |
| Amber Properties London Limited | Real estate | 2023 |
| Ambi Medics Ltd | Health & social care | 2023 |
| Ambiento Ltd | Professional & scientific | 2023 |
| Ambition Recruitment Services Limited | Administrative & support | 2009 |
| Amelie & Autumn Developments Ltd | Construction | 2025 |
| Amemo Limited | Information & communication | 2015 |
| Ameo Sycamore Ltd | Construction | 2023 |
| Ameretat Limited | Wholesale & retail | 2018 |
| American Seven Ltd | Wholesale & retail | 2021 |
| Amev Holdings Ltd | Construction | 2021 |
| Amic Limited | Construction | 2010 |
| Amies Kerala Kitchen Ltd | Hospitality | 2026 |
| Amir 22 Ltd | Real estate | 2020 |
| AMJ Controls Ltd | Manufacturing | 2025 |
| AMJ1 Holdings Limited | Real estate | 2015 |
| AMK Cooperate Limited | Hospitality | 2023 |
| AML Architects Limited | Professional & scientific | 2008 |
| Ammo Media Productions Ltd | Professional & scientific | 2012 |
| Amnikaa Limited | Real estate | 2024 |
| Amor Heating Limited | Construction | 2022 |
| Amora Real Estate Ltd | Real estate | 2026 |
| Amoro Ltd | Wholesale & retail | 2025 |
| Amour & Sons Limited | Construction | 2009 |
| AMP Electrical Services Limited | Construction | 2009 |
| Amped Associates Limited | Professional & scientific | 2016 |
| AMS Sutton Business Limited | Professional & scientific | 2017 |
| AMS Wimbledon Business Limited | Professional & scientific | 2019 |
| AMT Business Ltd | Wholesale & retail | 2018 |
| AMT Construction Ltd | Construction | 2024 |
| AMT Heating Ltd | Construction | 2010 |
| AMT Traders Limited | Wholesale & retail | 2025 |
| Amuse Events UK Ltd | Information & communication | 2018 |