| Arturo G&A Limited | Other services | 2024 |
| Artv Group Ltd | Financial services | 2025 |
| Artverse Advisory Services Limited | Professional & scientific | 2025 |
| Arundel Court (Beckenham Grove) Management Limited | Households | 1971 |
| Arusurarelucky Ltd | Real estate | 2025 |
| Arwhittaker Ltd | Health & social care | 2024 |
| ASA Insulation Limited | Construction | 2016 |
| Asap Glass and Glazing Limited | Construction | 2019 |
| Asatu - John Ltd | Health & social care | 2013 |
| ASC Gastroenterology Limited | Health & social care | 2026 |
| Asdrealty Ltd | Real estate | 2025 |
| ASH Court (Beaconsfield Road) Residents Company Limited | Real estate | 1989 |
| ASH Court (College Road Bromley) Residents Company Limited | Real estate | 1986 |
| Ashbar Enterprise Ltd | Health & social care | 2014 |
| Ashbourne Court (Beckenham) Management Limited | Households | 2000 |
| Ashbrookes Limited | Real estate | 2016 |
| Ashburton Service Centre Ltd | Wholesale & retail | 2000 |
| Ashford Property Consultants Ltd | Real estate | 2012 |
| Ashley Contractors Ltd | Construction | 2015 |
| Ashley Electrical Limited | Construction | 2009 |
| Ashton Court (Croydon) Ltd | Households | 2021 |
| Ashton Heights Management Limited | Households | 1981 |
| Ashview & Sons Ltd | Real estate | 2023 |
| Ashview Design Limited | Real estate | 2015 |
| Ashview Homes Ltd | Real estate | 2009 |
| Ashvika Property Services Ltd | Real estate | 2025 |
| Ashwell House (London) RTM Company Limited | Real estate | 2025 |
| Ashwin Properties Services Ltd | Real estate | 2024 |
| Ashwood Court Healthcare Ltd | Other services | 2002 |
| Ashwood Court Residents Limited | Households | 2001 |
| Ashwood Healthcare Ltd | Other services | 2002 |
| Ashwood Investments Limited | Financial services | 2025 |
| Ashwood Manor Healthcare Limited | Other services | 2017 |
| Ashwood Park Healthcare Ltd | Hospitality | 2005 |
| ASI Electrical Services Ltd | Construction | 2009 |
| Asiegbu Holdings Ltd | Real estate | 2025 |
| ASK Marine Ltd | Extraterritorial | 2025 |
| ASK QA Limited | Professional & scientific | 2017 |
| Aslan Academies Ltd | Education | 2026 |
| Aslan Property Investments Limited | Real estate | 2019 |
| Aspartacus Limited | Information & communication | 2020 |
| Aspectmutual Property Management Limited | Real estate | 1996 |
| Aspej Services Ltd | Health & social care | 2025 |
| Aspen Court (Croydon) RTM Company Limited | Households | 2013 |
| Aspen Eco-Sense Cleaning Solutions Ltd | Administrative & support | 2025 |
| Aspire 2 Inspire Group Ltd | Professional & scientific | 2017 |
| Aspire Construction London Ltd | Construction | 2022 |
| Aspiring 2 BE | Professional & scientific | 2010 |
| ASPIRING4EXCELLENCE Limited | Education | 2011 |
| Assembleia DE Deus NO Reino Unido | Information & communication | 2003 |
| Assk Properties Ltd | Real estate | 2019 |
| Assured Inventory Solutions Ltd | Real estate | 2023 |
| Assured Renovations and Maintenance Limited | Real estate | 1997 |
| Assured Temporary Works Ltd | Professional & scientific | 2026 |
| Aster Enterprises Limited | Professional & scientific | 2024 |
| Asterlink Developments Ltd | Real estate | 2018 |
| Asth Construction Ltd | Construction | 2026 |
| Aston Traders Ltd | Professional & scientific | 2016 |
| Aston Window Systems Limited | Construction | 2009 |
| Aswaryam Limited | Wholesale & retail | 2018 |
| Atel Q Limited | Professional & scientific | 2024 |
| Atelier Ochre Ltd | Professional & scientific | 2018 |
| ATELIER7 Ltd | Information & communication | 2017 |
| ATG Building Services Ltd | Construction | 2015 |
| Athelstan Ltd | Arts & recreation | 2021 |
| Athena Search Ltd | Administrative & support | 2016 |
| Athletic Army Limited | Wholesale & retail | 2017 |
| Atlant Ltd | Construction | 2021 |
| Atlantic Digital Ltd | Information & communication | 2021 |
| Atlantis Professional Services Limited | Administrative & support | 1997 |
| Atlas Bookkeeping & Consultancy Ltd | Professional & scientific | 2018 |
| ATM Couriers Ltd | Transport & logistics | 2021 |
| Atnami Ltd | Financial services | 2025 |
| Atomglen Limited | Wholesale & retail | 1989 |
| Atoz Delivery Services Limited | Transport & logistics | 2017 |
| Atterbury Limited | Households | 2000 |
| ATX Ventures Ltd | Wholesale & retail | 2021 |
| Atzara Ltd | Wholesale & retail | 2024 |
| Auda Ltd | Wholesale & retail | 2022 |
| Auda Medical Ltd | Education | 2013 |
| Audio Support LLP | | 2005 |
| Audio Visual Programming Consultancy Limited | Information & communication | 2009 |
| Audioxology Ltd | Information & communication | 2023 |
| Audit AID Limited | Information & communication | 2019 |
| Audrey House Management Company Limited | Real estate | 1983 |
| Augment Assets Limited | Real estate | 2026 |
| Augment Records Ltd. | Information & communication | 2023 |
| Auguste & Sons Ltd | Mining & quarrying | 2018 |
| Aukrux Limited | Wholesale & retail | 2015 |
| Aunest Holdings Limited | Professional & scientific | 2021 |
| AUNTIES2.0 Ltd | Health & social care | 2024 |
| Aura Court (Peckham) RTM Company Limited | Real estate | 2024 |
| Aura Stock Holding Limited | Wholesale & retail | 2025 |
| Aura Trading Contor Limited | Real estate | 2007 |
| Aurora Hospitality Ltd | Administrative & support | 2007 |
| Austerity Models Limited | Wholesale & retail | 2026 |
| Austin Commerce Limited | Wholesale & retail | 2017 |
| Authentic Group Ltd | Financial services | 2021 |
| Autism Consultancy Services Limited | Health & social care | 2014 |
| Auto Supreme Cleans Ltd | Wholesale & retail | 2025 |