| Allison Engineering Limited | Wholesale & retail | 1978 |
| Allison UK Holdings Limited | Financial services | 2020 |
| Alloy Express Ltd | Manufacturing | 2025 |
| Allsort Networks Ltd | Information & communication | 2019 |
| Allwell Success Limited | Health & social care | 2019 |
| Allyness Ltd | Wholesale & retail | 2020 |
| Ally’S Personal Touch Ltd | Wholesale & retail | 2022 |
| Alma Properties (Anglia) Holdings Ltd | Real estate | 2022 |
| Alma Properties (Anglia) Limited | Construction | 2018 |
| Almada Productions Limited | Extraterritorial | 2004 |
| Almond House Limited | Households | 1990 |
| Alnwick Limited | Manufacturing | 1997 |
| Aloks Designs Limited | Manufacturing | 2023 |
| Alonso Forwarding UK Ltd | Transport & logistics | 2023 |
| Alpha Constructions Group Limited | Construction | 2023 |
| Alpha Domain Limited | Real estate | 2020 |
| Alpha Dominion Limited | Health & social care | 2013 |
| Alpha One Digital Limited | Professional & scientific | 2022 |
| Alpha TT Limited | Financial services | 2023 |
| Alpho Ltd | Health & social care | 2025 |
| Alplas Limited | Manufacturing | 1965 |
| ALS Photographic Ltd | Professional & scientific | 2025 |
| ALS Plumbing and Building Services Limited | Construction | 2023 |
| Alsul Limited | Construction | 2013 |
| Altamira Services Ltd | Construction | 2026 |
| Alter Air Ventilation Ltd | Construction | 2018 |
| Altimus Group Ltd | Professional & scientific | 2026 |
| Altura Recruitment Limited | Administrative & support | 2023 |
| ALU Works Limited | Construction | 2024 |
| Alubo Ltd | Real estate | 2019 |
| ALW Cleaning Solutions Ltd | Administrative & support | 2020 |
| Alwayssmile Beauty Salon Ltd | Other services | 2026 |
| Alwie Group Ltd | Professional & scientific | 2026 |
| AM Fire Construction Ltd | Construction | 2022 |
| AM Sports Ground Services Limited | Other services | 2017 |
| AMA Dependable Limited | Health & social care | 2024 |
| Amalgamated Cleaning Services London Limited | Administrative & support | 2002 |
| Amari Constructions Limited | Construction | 2023 |
| Amazing Grace Personnel Limited | Health & social care | 2010 |
| Amazing Grace Streetlight Limited | Administrative & support | 2025 |
| Amazing Services Ltd | Other services | 2026 |
| Amazon Renewables Ltd | Construction | 2019 |
| Ambassador Cooked Meats Limited | Manufacturing | 1984 |
| Ambavi Healthcare Ltd | Health & social care | 2019 |
| Amber Partnership Ltd | Professional & scientific | 2023 |
| Ambril Limited | Other services | 2026 |
| Amcl (Brixton) Limited | Construction | 2015 |
| Amcl (Catford) Limited | Construction | 2015 |
| Amcl (Developments) Limited | Construction | 2019 |
| Amcl (Land Investment) Limited | Construction | 2013 |
| Amcl (New Homes) Limited | Construction | 2019 |
| Amcl (South East) Limited | Construction | 2013 |
| Amcl (Sydenham) Limited | Construction | 2015 |
| AME Solutions Ltd | Public administration | 2021 |
| Amelux Plumbing Ltd | Construction | 2025 |
| Ameluxcare Ltd | Health & social care | 2025 |
| Amexy Global Limited | Administrative & support | 2023 |
| AMG Contractors (Essex) Ltd | Construction | 2018 |
| AMG Group (Essex) Ltd | Construction | 2025 |
| Amica Projects Limited | Professional & scientific | 2014 |
| Amir & Co UK Limited | Administrative & support | 2016 |
| Amirson Investments Limited | Real estate | 2018 |
| Amity Luggage and Bags Ltd. | Manufacturing | 2013 |
| Amndlovu Limited | Health & social care | 2025 |
| Amoda (UK) Limited | Construction | 2014 |
| Amor Lingerie Limited | Manufacturing | 2009 |
| Amora Healthcare Ltd | Health & social care | 2021 |
| Amped Creative Ltd | Professional & scientific | 2022 |
| Ampleaward Limited | Wholesale & retail | 1995 |
| AMQ Professional Limited | Professional & scientific | 2014 |
| Amr-Lightace Group (UK) Ltd | Financial services | 2026 |
| AMS Accountancy Services Ltd | Professional & scientific | 2022 |
| AMY Muller Hygiene Limited | Health & social care | 2014 |
| Amy's Boutique and Tanning Ltd | Wholesale & retail | 2019 |
| Amy's Hair Salon Limited | Other services | 2020 |
| Amyv Ltd | Construction | 2019 |
| AN BIZ Solutions Limited | Professional & scientific | 2013 |
| Anabzil Private Limited | Real estate | 2020 |
| Anaco Plsea Limited | Health & social care | 2018 |
| Anagi Embroidery & Print Limited | Manufacturing | 2026 |
| Anagi Embroidery Limited | Manufacturing | 2016 |
| Analytics AI Solutions Limited | Information & communication | 2022 |
| Anayaz Traders Ltd | Wholesale & retail | 2024 |
| Anchor Contact and Mediation Services Ltd | Health & social care | 2026 |
| Ancors Properties Limited | Real estate | 2025 |
| AND John Limited | Transport & logistics | 2013 |
| Anderson COX Properties Limited | Real estate | 2025 |
| Anderson Paving Limited | Construction | 2018 |
| Anderson Yard Limited | Real estate | 2026 |
| Andial Co Ltd | Construction | 2018 |
| Andrav Technology Limited | Information & communication | 2016 |
| Andreev Flooring Ltd | Construction | 2025 |
| Andrei&David Limited | Transport & logistics | 2016 |
| Andrew Brown Drywall Limited | Construction | 2018 |
| Andrew Mark Aluminium Limited | Manufacturing | 2022 |
| Andrey Ltd | Transport & logistics | 2018 |
| Andv Limited | Construction | 2022 |
| Andy Contractor Ltd | Construction | 2018 |
| Andy Drywall Ltd | Construction | 2023 |
| Aneesaat Limited | Health & social care | 2023 |