| Adora Wellness Farm Limited | Other services | 2025 |
| ADR COV Limited | Professional & scientific | 2007 |
| Advance Intervention Practice CIC | Health & social care | 2026 |
| Advanced Cleaning (Midlands) Limited | Administrative & support | 2009 |
| Advanced Performance Management Ltd | Professional & scientific | 2024 |
| Adventurize Ltd | Wholesale & retail | 2011 |
| Aerdrop Ltd | Transport & logistics | 2017 |
| Aetheris Publishing Ltd | Information & communication | 2021 |
| AF Consultancy and Solutions Limited | Professional & scientific | 2024 |
| AFD Enterprises Ltd | Hospitality | 2019 |
| Affinity Financial Consulting UK Limited | Administrative & support | 2009 |
| Affodell Cyfyngedig Limited | Financial services | 2012 |
| Afml Dance Floor Hire Ltd | Manufacturing | 2024 |
| AGC Flooring Ltd | Wholesale & retail | 2024 |
| AH Bloxham Developments Limited | Construction | 2022 |
| Aidpoll Ltd. | Professional & scientific | 2004 |
| Air Conditioning and Electrical Limited | Energy | 2004 |
| Air Pressure Testing Ltd | Professional & scientific | 2004 |
| Airport Radio Taxis Ltd | Transport & logistics | 2020 |
| Airtrade Ltd | Extraterritorial | 2014 |
| Airware Limited | Extraterritorial | 2015 |
| AJ & AJ Consulting Limited | Professional & scientific | 2014 |
| AJ Distribution Services Ltd | Wholesale & retail | 2025 |
| AJE Property Ltd | Real estate | 2023 |
| AJT Advisory Limited | Real estate | 2026 |
| Akpj Holdings Limited | Real estate | 2021 |
| Akton Boundrie Group Limited | Professional & scientific | 2024 |
| Alacartcuterie Ltd | Hospitality | 2025 |
| Alacrity DB Limited | Financial services | 2014 |
| Alauna Ltd | Construction | 2023 |
| Albany Estates Ltd | Construction | 2026 |
| Albert E Sharp LLP | | 2008 |
| Albion Guild Ltd | Wholesale & retail | 2026 |
| Alderminster Farm Management Company Limited | Households | 1993 |
| Alderminster Kennels Ltd | Professional & scientific | 2015 |
| Algarhythm Biotech Ltd | Professional & scientific | 2025 |
| Align Property Recruitment Limited | Administrative & support | 2024 |
| ALL the Corners Ltd | Administrative & support | 2020 |
| ALL Things Green Limited | Administrative & support | 2014 |
| ALL Things Wild Limited | Arts & recreation | 2012 |
| Allect Investments Limited | Financial services | 2024 |
| Allegra Property Ltd | Real estate | 2020 |
| Allscope Garden Services Limited | Administrative & support | 2026 |
| Allure Aesthetics by Sarah Ltd | Other services | 2023 |
| Allwood Medical Ltd | Professional & scientific | 2022 |
| Alohomora Limited | Wholesale & retail | 2018 |
| Alphabet Avenue Ltd. | Information & communication | 2000 |
| Alphawerk Ltd | Information & communication | 2013 |
| Alscot Broadband Limited | Other services | 2012 |
| Alscot Limited | Other services | 2011 |
| Alspath Properties Limited | Construction | 1983 |
| Alsvior Global Limited | Information & communication | 2021 |
| Alterego Media Limited | Information & communication | 2019 |
| Aludum Ltd | Professional & scientific | 2021 |
| Alveston Developments Limited | Real estate | 1997 |
| Alveston Estates Ltd | Construction | 2021 |
| Alveston Homes Ltd | Construction | 2024 |
| Alveston Laundry Machines Limited | Wholesale & retail | 2024 |
| Alveston Park Management Company Limited | Households | 2006 |
| Alveston Promotions Ltd | Construction | 2025 |
| Alveston Properties Limited | Real estate | 2014 |
| Alvian Partnership Limited | Administrative & support | 2007 |
| Amax Construction Limited | Construction | 2004 |
| Amazon Office Management Limited | Professional & scientific | 2006 |
| Ambis Legal Support Services Limited | Administrative & support | 2014 |
| AMG Project Specialists Limited | Professional & scientific | 2015 |
| Amica Financial Wellbeing Limited | Financial services | 2020 |
| Amigo Awnings Ltd | Wholesale & retail | 2025 |
| Amlwch Asset Management Limited | Real estate | 2022 |
| Amorise Farms Limited | Agriculture & fishing | 2011 |
| Amsatarn Holdings Ltd | Financial services | 2024 |
| Amstone Ltd | Real estate | 2002 |
| Amuri Cafe Limited | Manufacturing | 2025 |
| AMW Lawn Care Limited | Administrative & support | 2013 |
| Amygdala Coaching Associates C.I.C. | Education | 2025 |
| AN Pizza Ltd | Hospitality | 2020 |
| Anactive Consultancy Limited | Professional & scientific | 2014 |
| Ancestral Superfoods UK Ltd | Manufacturing | 2021 |
| Andrew Mahon Ltd | Health & social care | 2019 |
| Andrew Scott Designer Jewellery Limited | Wholesale & retail | 1999 |
| Andrew Zarebski Silicone Consulting Ltd | Professional & scientific | 2022 |
| Andrews Clegg Limited | Hospitality | 2024 |
| Andy JK FX Ltd | Education | 2026 |
| Angelonki Ltd | Wholesale & retail | 2017 |
| Angle and Curve Limited | Manufacturing | 2009 |
| Anglia Dutch IT Limited | Information & communication | 2024 |
| Anglo Atlantic Media Limited | Administrative & support | 2003 |
| Anglo Danish OIL Company Limited | Extraterritorial | 2016 |
| Anglo Norwegian Holdings Limited | Financial services | 2021 |
| Angold Consulting Limited | Administrative & support | 2023 |
| ANI Financial Services Ltd | Professional & scientific | 2010 |
| Ankylosaurus Legal Limited | Professional & scientific | 2025 |
| Anna Mcgrath Consulting Limited | Professional & scientific | 2024 |
| Anne Roberts Design Ltd | Professional & scientific | 2024 |
| Annie Travel Adventures Limited | Administrative & support | 2026 |
| Anypallet (Midland) Ltd | Construction | 2007 |
| AP Generation Limited | Professional & scientific | 2015 |
| Apartmental Limited | Real estate | 2017 |
| Aperture Limited | Information & communication | 2021 |
| Apex Clearpoint Ltd | Administrative & support | 2026 |