| ALA Recruitment Solutions Limited | Administrative & support | 2011 |
| Alarm Masters Limited | Administrative & support | 2009 |
| Albany Court Residents Association Limited | Real estate | 1968 |
| Albury Ventures Ltd | Other services | 2018 |
| Alco LDN Ltd | Wholesale & retail | 2026 |
| Aldenholme Estate Residents Management Company Limited | Households | 2001 |
| Alder Alpha Limited | Wholesale & retail | 2022 |
| Alder Group Limited | Professional & scientific | 1981 |
| Alder Roofing Contractors Limited | Construction | 2009 |
| Alder Roofing Supplies Limited | Wholesale & retail | 1987 |
| Aldford Street Nominees Limited | Extraterritorial | 2007 |
| Alecarm Limited | Real estate | 2013 |
| Alexander James Projects Limited | Construction | 2017 |
| Alexander Pearce & SON (Plant) Limited | Construction | 1965 |
| Alexander Pearce Limited | Construction | 1960 |
| Alexander Rumsey Real Estate Limited | Extraterritorial | 2023 |
| Alexandra (Services) Limited | Real estate | 1947 |
| Alexandra's Home Ltd | Health & social care | 2025 |
| Alexib Investments | Financial services | 2026 |
| Alice Briggs Limited | Other services | 2016 |
| Alison Price and Company Limited | Hospitality | 1991 |
| Alitam Group Limited | Wholesale & retail | 2019 |
| ALL Aboard Consulting Ltd | Transport & logistics | 2022 |
| ALL Aboard! (UK) Ltd | Administrative & support | 2011 |
| ALL About Outdoor Living Limited | Construction | 2022 |
| ALL Aspects IT Ltd | Information & communication | 2014 |
| ALL Business Limited | Professional & scientific | 2019 |
| ALL Fuelz Limited | Professional & scientific | 2023 |
| Allhorse International Limited | Information & communication | 2019 |
| Allmanor Park (UK) Limited | Construction | 2017 |
| Allois Properties (Ewhurst) Limited | Real estate | 2016 |
| Allois Properties (Twickenham) Limited | Real estate | 2021 |
| Allois Properties Limited | Real estate | 2013 |
| Allsons Roofing Limited | Construction | 2017 |
| Almas Holdings Limited | Financial services | 2023 |
| Alpenglow Travel Limited | Administrative & support | 2014 |
| Alphabetum Limited | Financial services | 2022 |
| Alphagrep UK Limited | Information & communication | 2016 |
| Alta Concept Ltd | Professional & scientific | 2020 |
| Altered States FX Limited | Information & communication | 2013 |
| Altior Building Contractors Ltd | Construction | 2019 |
| Altium Associates Limited | Administrative & support | 2009 |
| Altum Valorem Limited | Wholesale & retail | 2020 |
| Always Guttering & Roofing Ltd | Construction | 2014 |
| Alzuti Ltd | Professional & scientific | 2018 |
| AM Business (Properties) Ltd | Real estate | 2023 |
| Amadeus Design and Building Limited | Construction | 2003 |
| Amalfi Finance Company Limited | Financial services | 2025 |
| Amalfi Holdings Limited | Financial services | 2025 |
| Amanda Flory Ltd | Other services | 2014 |
| Amber Lume Estates Limited | Real estate | 2024 |
| Amberley Hill Consulting Ltd | Professional & scientific | 2023 |
| Amberside Energy (Development) Ltd | Professional & scientific | 2021 |
| Amberside Power 2 Ltd | Construction | 2022 |
| AMD B.S. Limited | Construction | 2014 |
| Amerro Asset Management LLP | | 2005 |
| Ames-Rooks Limited | Wholesale & retail | 2012 |
| Amilano Limited | Real estate | 2018 |
| Amin High Ltd | Professional & scientific | 2023 |
| Amjad Electrical Services Ltd | Construction | 2025 |
| Amli Labs Limited | Information & communication | 2022 |
| Amorigin Limited | Information & communication | 2022 |
| Ampersand Partnership Limited | Financial services | 2011 |
| Amphora Australia Holdings Limited | Other services | 2018 |
| Amphora Finance Limited | Other services | 2018 |
| Amphora Intermediate II Limited | Other services | 2018 |
| AMT Investments Ltd | Professional & scientific | 2016 |
| AMW Estates Limited | Real estate | 2024 |
| Anaesthetic Technical Services Limited | Administrative & support | 2000 |
| Anarth Court Residents Association Limited | Administrative & support | 1978 |
| Anchanto Limited | Information & communication | 2021 |
| Andel Consultants Ltd | Professional & scientific | 2022 |
| Anderson Associates (UK) Limited | Professional & scientific | 2003 |
| Andover Western Limited | Construction | 2025 |
| Andrew Pollard Services Limited | Professional & scientific | 2015 |
| Andy Graves Strategy and Consulting Limited | Professional & scientific | 2025 |
| Andy James TV Limited | Information & communication | 2014 |
| Angas Court (Weybridge) Management Company Limited | Administrative & support | 1963 |
| Angel Media Ltd | Arts & recreation | 2021 |
| Angel Place Limited | Real estate | 2019 |
| Anglo African Ltd | Professional & scientific | 2021 |
| Anika Tech Solution Ltd | Information & communication | 2022 |
| Ankeeta Munsi Consulting Ltd | Professional & scientific | 2024 |
| Anker Productions Limited | Information & communication | 2007 |
| Annova Solutions Limited | Education | 2025 |
| Anomic Limited | Wholesale & retail | 2016 |
| ANP Architects Ltd | Professional & scientific | 2020 |
| Antev Limited | Professional & scientific | 2013 |
| Anthem London Ltd | Arts & recreation | 2025 |
| Anthony Gibson Coaching and Development Ltd | Professional & scientific | 2024 |
| Anthony Groves Holdings Limited | Financial services | 2018 |
| Anthony Mathews Limited | Professional & scientific | 2015 |
| Anthony Waring Limited | Health & social care | 2011 |
| Anthorpe Enterprises Limited | Manufacturing | 2012 |
| Antstorm Ltd | Information & communication | 2022 |
| Anymoment Limited | Hospitality | 2020 |
| Anything BUT Golf Ltd | Financial services | 2020 |
| Aoxomoxoa Limited | Information & communication | 2002 |
| AP Interior Design Limited | Professional & scientific | 2023 |
| AP2L 2405 Briercliffe Energy Storage Ltd | Energy | 2024 |