| Adiva Inc Limited | Professional & scientific | 2025 |
| ADK Healthcare Ltd | Health & social care | 2022 |
| ADO Solutions Ltd | Wholesale & retail | 2023 |
| Adrian Moore Surveying Limited | Professional & scientific | 2014 |
| Adrienne Photography Limited | Professional & scientific | 2011 |
| Adroit Building Services Limited | Construction | 2004 |
| Advance Digital Limited | Information & communication | 2022 |
| Advance Fire and Security Limited | Administrative & support | 1999 |
| Advanced Biologics Research Ltd | Professional & scientific | 2023 |
| Advanced Energy Monitoring Systems Limited | Manufacturing | 1981 |
| Advanced Exterior Plastics Limited | Construction | 2007 |
| Advanced KFS Holdings Limited | Financial services | 2019 |
| Advanced KFS Special Vehicles Limited | Wholesale & retail | 2015 |
| Advanced Locking and Locksmithing Limited | Administrative & support | 1984 |
| Advanced Locksmiths Ltd | Professional & scientific | 2000 |
| Advanced Office Interiors Limited | Construction | 2014 |
| Advanced Product Solutions Limited | Professional & scientific | 2011 |
| Advanced Shoulder and Elbow Solutions Limited | Health & social care | 2000 |
| Adventurous Paws Ltd | Other services | 2023 |
| Advoco Financial Limited | Extraterritorial | 2006 |
| Aeonic IT Ltd | Information & communication | 2018 |
| Aeos Infrastructure Planning Limited | Professional & scientific | 2017 |
| Aeroplane Workshop Ltd | Manufacturing | 2019 |
| Aesthetic Pro Mentoring Ltd | Health & social care | 2025 |
| Affinity Property Services Limited | Construction | 2026 |
| Affinity Residential Developments Ltd | Construction | 2023 |
| Afiv Ltd | Hospitality | 2016 |
| AFJ Trans 2 Ltd | Transport & logistics | 2018 |
| AG for the Nations Ltd | Other services | 2016 |
| AG S&T Ltd | Construction | 2016 |
| Ageas (UK) Limited | Financial services | 1973 |
| Ageas Insurance Limited | Financial services | 1939 |
| Ageas Insurance Staff Pension Scheme Trustee Limited | Financial services | 2025 |
| Ageas Retail Limited | Financial services | 1977 |
| Ageas Services (UK) Limited | Financial services | 1922 |
| Agentic Solutions Ltd | Information & communication | 2025 |
| Agents Giving | Health & social care | 2008 |
| Agility Agriculture Limited | Wholesale & retail | 2016 |
| Agincourt Securities Limited | Professional & scientific | 1997 |
| AGL Trading Ltd | Wholesale & retail | 2023 |
| Agricultural Machinery Repairs Ltd | Financial services | 2003 |
| Agricultural Produce Partners LLP | | 2021 |
| AGW Property Development Ltd | Construction | 2014 |
| Ahmad Tea Limited | Manufacturing | 1986 |
| AHT Marine Ltd | Professional & scientific | 2018 |
| Ahydra Ltd | Administrative & support | 2021 |
| AI Consult Ltd | Information & communication | 2024 |
| AI Digitals Tech Ltd | Information & communication | 2022 |
| Aienvisage Limited | Information & communication | 2026 |
| AIG Trades Ltd | Wholesale & retail | 2024 |
| AIK79 Ltd | Transport & logistics | 2019 |
| Aims Insights Limited | Information & communication | 2023 |
| Aipf (UK) Limited | Professional & scientific | 2012 |
| Air Maintenance Limited | Extraterritorial | 2005 |
| Airefine Ltd | Information & communication | 2025 |
| Airport Equipment Consultants Ltd | Administrative & support | 2020 |
| Airport Fire Safety Ltd | Professional & scientific | 2013 |
| Aisling Court Management Company Limited | Households | 2018 |
| Aisu Solutions Limited | Information & communication | 2025 |
| AJ Benjafield Limited | Wholesale & retail | 2006 |
| AJ Consurvices Limited | Professional & scientific | 2022 |
| AJ Elite Marketing Ltd | Professional & scientific | 2023 |
| AJ IT Services Ltd | Information & communication | 2018 |
| AJ King Radiology Limited | Health & social care | 2015 |
| AJ Motors (Southern) Limited | Wholesale & retail | 2024 |
| AJC Bathrooms Limited | Construction | 2003 |
| AJH Project Management Limited | Professional & scientific | 2019 |
| AJL Carpentry and Building Ltd | Construction | 2021 |
| AJN Building Services Ltd | Construction | 2023 |
| AJR Civil & Marine Limited | Construction | 2016 |
| Ajrdr Limited | Professional & scientific | 2024 |
| AK Logistics South Ltd | Transport & logistics | 2026 |
| Akinscare Ltd | Health & social care | 2017 |
| Akorn & Oake Ltd | Other services | 2022 |
| Al-Ilm Consultancy LLP | | 2011 |
| Alacris Project Services Limited | Professional & scientific | 2014 |
| Alan Evans Coaching Limited | Other services | 2021 |
| Alan Evans Consulting Limited | Professional & scientific | 2019 |
| Alan Hand Car Wash Ltd | Professional & scientific | 2016 |
| Alaya Renovations Ltd | Construction | 2026 |
| ALB Electrical Limited | Construction | 2003 |
| ALB Property and Lettings Ltd | Real estate | 2025 |
| Albion 4C Limited | Wholesale & retail | 2006 |
| Albion Components Ltd | Wholesale & retail | 2010 |
| Albro Systems Ltd | Construction | 2017 |
| Alcaraz Creative Studio Ltd | Information & communication | 2023 |
| Alcatraz Holdings Limited | Administrative & support | 2002 |
| Alchemist Residential Limited | Real estate | 2016 |
| Alda Plastics Limited | Manufacturing | 2007 |
| Aldenoak Consultancy Services Limited | Professional & scientific | 2017 |
| Aldermoor Investments Ltd | Real estate | 2018 |
| Aldridge Building Systems Limited | Administrative & support | 2014 |
| Alesyo WIN Ltd | Wholesale & retail | 2025 |
| Aleta Limited | Wholesale & retail | 2003 |
| Alex Gard Fitness & Health Ltd | Other services | 2022 |
| Alex Kimber Design Ltd | Manufacturing | 2021 |
| Alex Munday Planning Ltd | Professional & scientific | 2026 |
| Alex Nicholas Property Limited | Real estate | 2020 |
| Alex Ricketts Ltd | Professional & scientific | 2019 |
| Alex Stevens Limited | Administrative & support | 2009 |