| Ascot Drummond (Holdings) Limited | Professional & scientific | 2000 |
| Ascot Drummond (UK) Limited | Professional & scientific | 2000 |
| Ascot Drummond Directors Limited | Extraterritorial | 1999 |
| Ascot Drummond Nominees Limited | Extraterritorial | 2001 |
| Ascot Drummond Secretarial Limited | Extraterritorial | 1999 |
| Ascot Laboratories Limited | Manufacturing | 2011 |
| ASH Construction (Hants) Limited | Construction | 2016 |
| ASH Court Community Limited | Health & social care | 1994 |
| ASH K Associates Ltd | Administrative & support | 2017 |
| Ashden Projects Ltd | Construction | 2011 |
| Ashdown Estate Property Management Co. Limited | Real estate | 1969 |
| Ashleigh Latter Art Ltd | Arts & recreation | 2026 |
| Ashor Energy Publishing Limited | Information & communication | 2017 |
| Ashraf Cars Limited | Transport & logistics | 2023 |
| Asian Fashion Apparels and Sourcing Limited | Professional & scientific | 2012 |
| ASK the Plumber London Limited | Construction | 2015 |
| ASLAM909 & Co Limited | Real estate | 2024 |
| Aspella Limited | Real estate | 1996 |
| Aspen Village Limited | Health & social care | 2002 |
| Aspire Design (Nottingham) Ltd | Professional & scientific | 1999 |
| ASR IT Consultancy Ltd | Information & communication | 2019 |
| Asrk Consultants Ltd | Professional & scientific | 2019 |
| Asrk Property Ltd | Real estate | 2018 |
| Asseily Ventures Limited | Financial services | 2018 |
| Asset Place Ltd | Real estate | 2016 |
| Assign Group Ltd | Administrative & support | 2014 |
| Assistifi Ltd | Administrative & support | 2024 |
| Association of British Investigators Limited(The) | Other services | 1970 |
| Assous Holdings Ltd | Real estate | 2019 |
| Assura Protect Limited | Financial services | 2013 |
| Assured Cooling Essex Ltd | Construction | 2025 |
| Assured Heating Essex Limited | Construction | 2013 |
| Astera Mews Management Services Limited | Households | 2021 |
| Aston Court Hotel Ltd | Hospitality | 2023 |
| Aston Height LLP | | 2016 |
| Aston Heights (Bedford) Limited | Other services | 2016 |
| Astrid Technologies Limited | Information & communication | 2011 |
| Astrum Capital Investments Limited | Real estate | 2011 |
| Asyn Limited | Wholesale & retail | 2002 |
| Aszano Limited | Professional & scientific | 2018 |
| AT & GD Commercial Services Ltd | Manufacturing | 2018 |
| AT Online Media Limited | Extraterritorial | 2012 |
| AT44 Services Ltd | Arts & recreation | 2026 |
| ATA Kyriakou Limited | Real estate | 2026 |
| Atalia Childcare Limited | Health & social care | 2025 |
| Atar Penthouses Limited | Construction | 2020 |
| Atarah Management Services Limited | Hospitality | 2019 |
| Atauktravel Ltd | Transport & logistics | 2025 |
| ATD Consultancy Ltd | Information & communication | 2022 |
| Atdt Property Ltd | Real estate | 2021 |
| Ateagal Estate Ltd | Real estate | 2016 |
| Athena Project Partnership Ltd | Professional & scientific | 2025 |
| Athena Property Management & Investment Ltd | Real estate | 2020 |
| Athene Lettings Limited | Real estate | 2025 |
| Athene New Build Limited | Real estate | 2017 |
| Athenico Limited | Information & communication | 2025 |
| Athrat Limited | Wholesale & retail | 2016 |
| Atia Partners Limited | Administrative & support | 2025 |
| ATK Direct Ltd | Wholesale & retail | 2019 |
| Atkinson Residential Limited | Real estate | 2020 |
| Atlantic Contracts Limited | Construction | 2001 |
| Atlantic Pacific Trading (APT) Limited | Wholesale & retail | 2010 |
| Atlas Health Ltd | Education | 2019 |
| Atlas Tech Ltd | Information & communication | 2019 |
| Atmosfair Ltd. | Construction | 2020 |
| Atomo TV Ltd | Information & communication | 2015 |
| ATP Building's Construction Ltd | Construction | 2015 |
| Atram Financial Ltd | Financial services | 2021 |
| ATRI7 3 Limited | Real estate | 2021 |
| ATRI7 5 Limited | Real estate | 2023 |
| ATRI7 6 Limited | Real estate | 2024 |
| ATRI7 8 Limited | Real estate | 2024 |
| ATRI7 9 Limited | Real estate | 2024 |
| Atrium Tax Consultancy Group International Ltd | Information & communication | 2019 |
| Attari Group Limited | Real estate | 2018 |
| Attenborough Jewellers Limited | Wholesale & retail | 1940 |
| Atticus Innovation Limited | Administrative & support | 2008 |
| ATV Nominee Ltd | Other services | 2011 |
| Aubrey Court Management Company Limited | Real estate | 2006 |
| Aubrey Homes Developments Limited | Construction | 2018 |
| Audacious Garden Services Ltd | Administrative & support | 2025 |
| Audit & Risk Professionals LLP | | 2014 |
| AUM Logistics Limited | Transport & logistics | 2024 |
| Aura Brand Management Limited | Administrative & support | 2017 |
| Auralern Limited | Education | 2004 |
| Aurient Medical Consulting Ltd | Health & social care | 2017 |
| Aurum Sports Management Limited | Professional & scientific | 2024 |
| Ausculto Limited | Professional & scientific | 2015 |
| Austen House Borehamwood Management Limited | Households | 2022 |
| Austify Ltd | Information & communication | 2018 |
| Autel Europe UK Ltd | Wholesale & retail | 2021 |
| Authentic Mexican Ltd | Hospitality | 2021 |
| Authorised Publications Media Ltd | Manufacturing | 2019 |
| Auto Capital Limited | Wholesale & retail | 2006 |
| Automotive and Maritime Hydrogen Solutions Ltd | Administrative & support | 2011 |
| Autoselamine Limited | Wholesale & retail | 2025 |
| Auxilium Business Solutions Limited | Information & communication | 2025 |
| AV Building Construction Limited | Construction | 2013 |
| AV Private Limited | Real estate | 2021 |
| AV Property (UK) Limited | Real estate | 2015 |