| ACH Grapes Limited | Manufacturing | 2023 |
| Achievements of Canterbury Limited | Other services | 2015 |
| Acol House Ltd | Wholesale & retail | 2020 |
| Acorn Everywhere Ltd | Wholesale & retail | 2025 |
| Acrise Electrical Services Limited | Construction | 2018 |
| Acrobat Corporate Services Ltd. | Professional & scientific | 1998 |
| ACS Consulting Services Limited | Administrative & support | 2017 |
| ACS Inns Ltd | Hospitality | 2025 |
| Actineo Consulting LLP | | 2015 |
| Active Audio Visual Installations Limited | Administrative & support | 2005 |
| Active Focus Ltd | Information & communication | 2021 |
| Active Pharma Support Limited | Professional & scientific | 2010 |
| Acuwell Alternative Healthcare Limited | Health & social care | 2020 |
| AD Management Advantage Limited | Financial services | 2019 |
| ADA & INA Limited | Wholesale & retail | 2012 |
| ADA Pazari Catering Ltd | Hospitality | 2024 |
| Adai MC & C Ltd | Other services | 2017 |
| Adam & Hayley Contractors Ltd | Construction | 2019 |
| Adam Daniel Consultancy Ltd | Arts & recreation | 2012 |
| Adam Daniel Health and Performance Ltd | Arts & recreation | 2011 |
| Adams & SON (Holdings) Limited | Real estate | 1961 |
| Adams Home Centre Limited | Wholesale & retail | 1996 |
| Adaptive Project Teams Limited | Professional & scientific | 2008 |
| Adastra HR Ltd | Professional & scientific | 2012 |
| ADD to Event Limited | Information & communication | 2014 |
| Addington Ltd | Wholesale & retail | 2022 |
| Adesewa Limited | Financial services | 2024 |
| ADH Holdings Limited | Financial services | 2026 |
| Admill Investments Limited | Hospitality | 1961 |
| Admiral House Management Co Ltd | Real estate | 2013 |
| Adorned Jewellery Limited | Wholesale & retail | 2025 |
| Adotc Design Limited | Professional & scientific | 2019 |
| ADP Psychological Services Limited | Health & social care | 2008 |
| Adrianet Course Ltd | Information & communication | 2025 |
| Adrianna Al-Kobecy Limited | Wholesale & retail | 2024 |
| Adrin Property Ltd | Real estate | 2025 |
| Adstringo Limited | Professional & scientific | 2023 |
| Adsum AI Ltd | Information & communication | 2025 |
| Adtrex Ltd | Extraterritorial | 2010 |
| Advaita Ltd | Hospitality | 2023 |
| Advance Healthcare Logistics Limited | Health & social care | 2010 |
| Advantage Licensed Retail Ltd | Hospitality | 2003 |
| Advision TV Limited | Information & communication | 2004 |
| AE Building Services Limited | Construction | 2005 |
| Aedifex Solutions Limited | Construction | 2026 |
| Aerial Insight Solutions Limited | Professional & scientific | 2024 |
| Aerospace International Ltd | Manufacturing | 2025 |
| Aesthae Muse Ltd | Other services | 2025 |
| Aether Medical Gases Holding Company Limited | Financial services | 2020 |
| Aether Medical Gases Limited | Manufacturing | 2010 |
| Affinity Asset Management Ltd | Extraterritorial | 2014 |
| Afrenaissance Limited | Wholesale & retail | 2022 |
| Afrisale Distributors Ltd | Wholesale & retail | 2025 |
| Aftercare Solutions Ltd | Other services | 2021 |
| AG Topco Limited | Administrative & support | 2024 |
| Agape Online Group Limited | Financial services | 2024 |
| Agape Online Ltd | Wholesale & retail | 2012 |
| Agarathi Ltd | Information & communication | 2023 |
| AGC Computers Limited | Information & communication | 2016 |
| AGC International Ltd | Professional & scientific | 2024 |
| AGC IT Ltd | Information & communication | 2013 |
| AGE UK Canterbury | Health & social care | 2002 |
| Agemco Ltd | Administrative & support | 2010 |
| Agile Consulting Services Limited | Information & communication | 2016 |
| Agora Models Ltd | Wholesale & retail | 2020 |
| Agri-Starr Limited | Agriculture & fishing | 2016 |
| Agricare Ltd | Wholesale & retail | 2016 |
| Agricola Storage Limited | Transport & logistics | 2010 |
| AGW BIZ U.K Ltd | Real estate | 2025 |
| AHC Investment Holdings Limited | Financial services | 2020 |
| AHC Property Limited | Real estate | 2020 |
| Ahmad ALI Shop Limited | Wholesale & retail | 2025 |
| Ahmad Corporation Limited | Wholesale & retail | 2025 |
| AHO Wincheap Ltd | Hospitality | 2023 |
| AI ALI Goods Limited | Wholesale & retail | 2024 |
| AI Science Tutors Limited | Education | 2025 |
| AI Security Services Ltd | Administrative & support | 2024 |
| AIA Transport Ltd | Administrative & support | 2023 |
| Aidan Willis Films Ltd | Information & communication | 2024 |
| Aiim Research and Training Ltd | Administrative & support | 2024 |
| Ainsley Gill Dispute Resolution Limited | Professional & scientific | 2021 |
| Aiple Limited | Wholesale & retail | 2025 |
| Airdat Ltd | Information & communication | 2015 |
| Airecare Limited | Construction | 2006 |
| Airhis Healthcare Ltd | Health & social care | 2024 |
| Airhive Ltd | Professional & scientific | 2022 |
| Airhost Agency Ltd | Real estate | 2018 |
| Airside Data & Training Ltd | Information & communication | 2006 |
| Airsoft Evolution Ltd | Arts & recreation | 2021 |
| Aissa Limited | Health & social care | 2012 |
| Ajwa Ethnic Food Limited | Hospitality | 2018 |
| Ak&Co Studio Ltd | Wholesale & retail | 2017 |
| AK17 Construction Ltd | Construction | 2025 |
| AKH3 Investments Ltd | Real estate | 2025 |
| Akhh Holdings Limited | Administrative & support | 2023 |
| AL Russell Holdings Limited | Construction | 2023 |
| Al's Pals Dogs Ltd | Other services | 2025 |
| Alaba IGE Limited | Health & social care | 2023 |
| Alan Knott Enterprises Limited | Financial services | 1973 |
| Alaturka Canterbury Ltd | Hospitality | 2014 |