| ALI KA (39) Ltd | Hospitality | 2012 |
| ALI Mairaj Enterprises Limited | Real estate | 2025 |
| Aliam Electrical Solutions Ltd | Construction | 2020 |
| Aliane Construction Ltd | Construction | 2026 |
| Alibaba Health Ltd | Health & social care | 2022 |
| Alice Construction Ltd | Construction | 2024 |
| Align Consultancy Ltd | Professional & scientific | 2025 |
| Alina Wallace Communications Limited | Professional & scientific | 2019 |
| Alinabuilder Ltd | Construction | 2025 |
| Alium Medical Limited | Wholesale & retail | 2001 |
| Alivian Capital Limited | Professional & scientific | 2021 |
| Alizurum Limited | Financial services | 2024 |
| Alkaid Global Limited | Wholesale & retail | 2022 |
| ALL Access Tree Services Ltd | Administrative & support | 2021 |
| ALL Good Things Limited | Information & communication | 2024 |
| ALL OUT Holidays Ltd | Administrative & support | 2019 |
| ALL Star Sports Academy Ltd | Education | 2026 |
| ALL the Pronouns Limited | Wholesale & retail | 2020 |
| ALL2STAY Ltd | Real estate | 2018 |
| Allaboutantenatal Limited | Education | 2019 |
| Allcool (London) Limited | Other services | 2002 |
| Allcool Services (London) Limited | Construction | 2016 |
| Alliance Investments Limited | Real estate | 1986 |
| Allied Leisure Solutions Limited | Professional & scientific | 2010 |
| Allkeen Limited | Professional & scientific | 2024 |
| Allround Dental Ltd | Health & social care | 2023 |
| Allsell Ltd | Wholesale & retail | 2024 |
| Ally Accountants Ltd | Professional & scientific | 2020 |
| Ally Property Solutions Ltd | Real estate | 2025 |
| Alma Escapes Ltd | Health & social care | 2019 |
| Aloha Ikigai Ltd | Professional & scientific | 2024 |
| Alpaca Mango Ltd | Education | 2022 |
| Alpha Cars (Herts) Limited | Transport & logistics | 2019 |
| Alpha Lexis Law Firm LLP | | 2009 |
| Alpha Lexis LLP | | 2009 |
| Alpha Project Consultants Limited | Professional & scientific | 2013 |
| Alpha Residential Care Ltd | Health & social care | 2015 |
| Alphafine Services Limited | Hospitality | 1992 |
| Alphaville Productions Limited | Information & communication | 2009 |
| Alpine House (Stanmore) Management Limited | Households | 2017 |
| Alpine House RTM Company Limited | Households | 2019 |
| Alshafi Properties Limited | Real estate | 2021 |
| Altair Partners Limited | Health & social care | 2021 |
| Altea Construction Ltd | Construction | 2023 |
| Altercity Properties Limited | Construction | 1998 |
| Alternative Bridging (Management) Limited | Financial services | 2019 |
| Alternative Bridging (UK 1) Limited | Financial services | 2014 |
| Alternative Bridging (UK 2) Limited | Financial services | 2016 |
| Alternative Bridging Corporation (Cheval) Limited | Financial services | 2001 |
| Alternative Bridging Corporation Limited | Financial services | 2010 |
| Alternative Commercial Mortgages Limited | Financial services | 2026 |
| Alternative Development Finance Limited | Financial services | 2021 |
| Althea MMJ UK Ltd | Administrative & support | 2017 |
| Altus Bromley Road Limited | Real estate | 2014 |
| ALU Holdings Limited | Real estate | 2018 |
| ALU Lettings Limited | Real estate | 2025 |
| Alumen Electrical Ltd | Construction | 2025 |
| Aluminium in Fenestration Limited | Information & communication | 2016 |
| Always Every Day Solutions Ltd | Professional & scientific | 2023 |
| Alwyn House Publishing Limited | Information & communication | 2019 |
| ALX Marketing Limited | Health & social care | 2021 |
| AM Beauty Ltd | Other services | 2025 |
| AM Learning Solutions Ltd | Information & communication | 2023 |
| AM Restaurant Ltd | Hospitality | 2019 |
| Am:Pm Events Limited | Arts & recreation | 2025 |
| AMA Design Services Ltd | Professional & scientific | 2020 |
| AMA Web Design Services Ltd | Professional & scientific | 2022 |
| Amaaras Properties Limited | Real estate | 2024 |
| Amabala Productions Limited | Arts & recreation | 1999 |
| Amafhh Property Investments Limited | Real estate | 2018 |
| Amanita Limited | Wholesale & retail | 2018 |
| Amaranto Investments Limited | Real estate | 2021 |
| Amariei Ltd | Construction | 2018 |
| Amaya Consultancy Limited | Professional & scientific | 2019 |
| Amazing Beyond Ltd | Wholesale & retail | 2017 |
| Amberose Limited | Wholesale & retail | 2016 |
| Ambia Aesthetics Ltd | Health & social care | 2019 |
| Ambika Restaurant Limited | Hospitality | 2025 |
| Ambitious Systems Limited | Information & communication | 2023 |
| Ambro Limited | Wholesale & retail | 1997 |
| Ambulance Intelligence Limited | Information & communication | 2026 |
| Amco Wholesale Limited | Wholesale & retail | 2008 |
| AMD Futures Ltd | Real estate | 2021 |
| AMD Healthcare Services Limited | Health & social care | 2019 |
| AMD UK Group Limited | Financial services | 2025 |
| Ameera Real Estate Limited | Administrative & support | 2009 |
| Ameerah Properties Investment Limited | Real estate | 2006 |
| Ameibein Limited | Professional & scientific | 2011 |
| Amelia Flooring Ltd | Construction | 2015 |
| Amelis Properties Ltd | Real estate | 2022 |
| Amer Khan Ltd | Health & social care | 2010 |
| American-Shopping Limited | Wholesale & retail | 2018 |
| Americraft (Boca) Limited | Administrative & support | 2026 |
| Americraft (Operations) Limited | Administrative & support | 2026 |
| Americraft Properties Limited | Administrative & support | 2014 |
| Amersol Limited | Hospitality | 2015 |
| AMG Security Ltd | Administrative & support | 2021 |
| AMI Project Development Limited | Construction | 2018 |
| Amick Productions Limited | Arts & recreation | 2015 |
| Amigos Network Limited | Professional & scientific | 2019 |