| Anglo Iberian Aviation Limited | Administrative & support | 2022 |
| Animation Arashi Limited | Information & communication | 2020 |
| Animus Health Technologies Ltd | Information & communication | 2024 |
| Ankhero Ltd | Information & communication | 2020 |
| Anna Vaccaro Productions Limited | Information & communication | 2015 |
| Anne-Marie Lucas Editing Limited | Information & communication | 2017 |
| Another Day Productions Limited | Information & communication | 2011 |
| Antlergold Limited | Professional & scientific | 2020 |
| Antlers Management Ltd | Professional & scientific | 2012 |
| Appfocused Limited | Information & communication | 2016 |
| Appia Consulting Limited | Information & communication | 2012 |
| Apples Operational Support Limited | Professional & scientific | 2013 |
| Approach Occupational Health Ltd | Health & social care | 2020 |
| Apricot Systems Ltd | Information & communication | 2021 |
| April Blossoms Ltd | Arts & recreation | 2009 |
| Arasto Ltd | Health & social care | 2016 |
| Arbitrage Analytics Solutions Ltd | Information & communication | 2024 |
| Arcane Bespoke Limited | Wholesale & retail | 2015 |
| Architecture : WK Limited | Professional & scientific | 2003 |
| Arcupang Limited | Professional & scientific | 2019 |
| Arden Accountancy Limited | Professional & scientific | 2013 |
| Arden Advisors Limited | Professional & scientific | 2014 |
| Arden Knight LLP | | 2022 |
| Arete Health and Performance Ltd | Arts & recreation | 2017 |
| Aretsia Tiles Ltd | Wholesale & retail | 2023 |
| Arim Böcük Ltd | Information & communication | 2023 |
| Arka 12 Ltd | Manufacturing | 2024 |
| Armillary Consulting Ltd | Professional & scientific | 2014 |
| Arminca Limited | Agriculture & fishing | 2008 |
| Armitage Management Limited | Real estate | 2024 |
| Arnison Consulting Limited | Information & communication | 2011 |
| Aromaden Limited | Health & social care | 1999 |
| Arrei Ltd | Other services | 2023 |
| Arshee Ltd | Wholesale & retail | 2025 |
| Art House Galleries Community Interest Company | Real estate | 2021 |
| Art of Work Solutions Limited | Professional & scientific | 2017 |
| Artainability Limited | Professional & scientific | 2023 |
| AS Screeding Solutions Limited | Construction | 2025 |
| Ascence Limited | Professional & scientific | 2009 |
| Asdco Limited | Professional & scientific | 2025 |
| Asgard Plumbing and Pipefitting Professionals Ltd | Construction | 2026 |
| Ashchurch Residents Company Limited | Households | 1973 |
| Asheppee Consultancy Ltd | Education | 2022 |
| Ashmore Health Limited | Health & social care | 2020 |
| Ashmore Search Ltd | Administrative & support | 2025 |
| Ashop Services Ltd | Real estate | 2020 |
| Asian Choice International Limited | Wholesale & retail | 2019 |
| Asra Food & Wine Limited | Wholesale & retail | 2024 |
| Assist London Limited | Professional & scientific | 2016 |
| Asstra UK Ltd | Transport & logistics | 2020 |
| Astrid-Nathalie Anne Carole Pearce Ltd | Extraterritorial | 2021 |
| Atelier 83 Ltd | Manufacturing | 2024 |
| Atelier Alfa Corse Ltd | Wholesale & retail | 2024 |
| Athena CAL Limited | Professional & scientific | 2024 |
| Athletemannies Limited | Administrative & support | 2015 |
| Atkins & Palmer Limited | Professional & scientific | 2017 |
| Atlantic Xiyang Limited | Wholesale & retail | 2014 |
| Atlas Removals & Handyman Ltd | Transport & logistics | 2016 |
| Atlas Smart Energy Ltd | Professional & scientific | 2020 |
| Atticus Property Development Limited | Construction | 2020 |
| AU LAC Designs Limited | Wholesale & retail | 2000 |
| Aubury Place (Chiswick) Management Company Limited | Households | 2018 |
| Audient Marketing Ltd | Professional & scientific | 2020 |
| Audio Illusion Ltd | Information & communication | 2015 |
| Audouy Consulting Limited | Information & communication | 2010 |
| August Rock Limited | Professional & scientific | 2021 |
| Aura Laboratories Ltd | Wholesale & retail | 2025 |
| Aural Intrigue Limited | Professional & scientific | 2008 |
| Aurora Market Research Limited | Professional & scientific | 2001 |
| Authentic Edge Coaching Ltd | Administrative & support | 2022 |
| AUX Technologies Ltd | Information & communication | 2017 |
| Avalon PR Limited | Professional & scientific | 2023 |
| Aventir Limited | Information & communication | 2013 |
| Avernus North West Ltd | Wholesale & retail | 2023 |
| Aviationforex Limited | Administrative & support | 2014 |
| Avon Commercial Limited | Financial services | 1992 |
| Avvyland Ltd | Information & communication | 2023 |
| Awesome Kids Limited | Education | 2016 |
| Awesome Studios (Activities) Limited | Arts & recreation | 2015 |
| Awesome Studios (Teddington) Limited | Real estate | 2019 |
| AWM22 Consulting Limited | Professional & scientific | 2015 |
| Azuro Consulting Limited | Professional & scientific | 2011 |
| B Executed Management Ltd | Construction | 2022 |
| B&C London Investment Solutions Limited | Real estate | 2014 |
| Bachhiya Group Ltd | Manufacturing | 2025 |
| Backstreet Dojo BJJ Ltd | Education | 2024 |
| Backstreet Dojo C.I.C. | Education | 2022 |
| Badgemoor Ltd | Real estate | 2010 |
| Badger Barrett Properties Limited | Real estate | 2019 |
| Badi-Ul-Jamal Innovations Ltd | Wholesale & retail | 2024 |
| Baker Neff Limited | Professional & scientific | 2024 |
| Balfour Events Limited | Professional & scientific | 2020 |
| Ball Orthopaedics Ltd | Health & social care | 2022 |
| Bambino (UK) Limited | Extraterritorial | 1987 |
| Bantas Limited | Information & communication | 2015 |
| Barackwise Construction Ltd | Construction | 2024 |
| Bareform Brands Limited | Manufacturing | 2025 |
| Barouki Holding Limited | Financial services | 2024 |
| Bartlett and Partners Limited | Real estate | 2016 |
| Baserelay Ltd | Information & communication | 2010 |