| Assetfinance December (F) Limited | Financial services | 1969 |
| Assetfinance December (H) Limited | Financial services | 1989 |
| Assetfinance December (R) Limited | Financial services | 2002 |
| Assetfinance June (D) Limited | Financial services | 1976 |
| Assetfinance March (D) Limited | Financial services | 1980 |
| Assetfinance March (F) Limited | Financial services | 1980 |
| Assetfinance September (G) Limited | Financial services | 1973 |
| Assetium Ltd | Professional & scientific | 2022 |
| Assetra Group Ltd | Real estate | 2026 |
| Assi Syan Ltd | Construction | 2022 |
| Assi Technical Services Ltd | Manufacturing | 2019 |
| Assign Limited | Wholesale & retail | 1987 |
| Assign Medicare Limited | Health & social care | 2011 |
| Assist a Landlord Ltd | Professional & scientific | 2022 |
| Assist Agile Limited | Administrative & support | 2017 |
| Assist Building & Maintenance Ltd | Construction | 2025 |
| Assist Car Body Repairs Ltd | Wholesale & retail | 2025 |
| Assist Facilities Services Limited | Administrative & support | 2015 |
| Assist FS Ltd | Administrative & support | 2013 |
| Assist Holdings Limited | Financial services | 2025 |
| Assist Housing Ltd | Hospitality | 2015 |
| Assist Landlords Legal Ltd | Real estate | 2016 |
| Assist Operational Support Ltd | Professional & scientific | 2020 |
| Assist Transport Limited | Professional & scientific | 2023 |
| Assist Travel Limited | Other services | 2011 |
| Assist VIP Travel Limited | Other services | 2016 |
| Assisted Housing Limited | Real estate | 2025 |
| Assisted Living South West Limited | Health & social care | 2008 |
| Assisting Travel Ltd | Transport & logistics | 2019 |
| Assistiva Care Ltd | Health & social care | 2024 |
| Assk Medical Solutions Ltd | Health & social care | 2020 |
| Assn Trading Limited | Wholesale & retail | 2024 |
| Associa Fire Protection Limited | Construction | 2020 |
| Associate Properties Limited | Real estate | 2000 |
| Associated Addiction Services Ltd | Health & social care | 2026 |
| Associated Architects UK Limited | Professional & scientific | 2023 |
| Associated Central Taxis (Gloucester) Ltd | Transport & logistics | 2010 |
| Associated Electrical Industries Limited | Financial services | 1899 |
| Associated Legal Consultants Limited | Professional & scientific | 2011 |
| Associated Services Ltd | Construction | 2024 |
| Associated Tyre Specialists (Investment) Limited | Financial services | 1990 |
| Association for Character Education Limited | Education | 2016 |
| Association of Air Ambulances Limited | Other services | 2012 |
| Association of British-Azerbaijani Doctors and Dentists CIC | Other services | 2025 |
| Association of Camerados Community Interest Company | Health & social care | 2018 |
| Association of Defence General & Vascular Surgeons Ltd | Administrative & support | 2023 |
| Association of Ex-Round Tablers' Clubs Limited | Other services | 2025 |
| Assots. Limited | Wholesale & retail | 2012 |
| Asstana Ltd | Wholesale & retail | 2024 |
| Assumpsit Limited | Professional & scientific | 2011 |
| Assura One Limited | Administrative & support | 2015 |
| Assurance Healthcare Ltd | Administrative & support | 2012 |
| Assurance Housing Ltd | Real estate | 2016 |
| Assure Dialysis Services Ltd | Health & social care | 2013 |
| Assure Environmental Limited | Professional & scientific | 2025 |
| Assure Holdings Group Limited | Financial services | 2025 |
| Assure Homes Snagging Ltd | Construction | 2021 |
| Assure Housing Ltd | Administrative & support | 2017 |
| Assure ME CIC | Health & social care | 2024 |
| Assure Support Ltd | Real estate | 2021 |
| Assured Cars Birmingham Limited | Wholesale & retail | 2020 |
| Assured Cars Supermarket Limited | Wholesale & retail | 2018 |
| Assured Cars Supermarket Trade UK Limited | Wholesale & retail | 2019 |
| Assured Estates Ltd | Administrative & support | 2014 |
| Assured Financial Consultancy Ltd | Financial services | 2021 |
| Assured H-C Solutions Ltd | Health & social care | 2017 |
| Assured Housing Ltd | Households | 2007 |
| Assured Interest Limited | Information & communication | 2019 |
| Assured Investments Limited | Education | 2012 |
| Assured Landscape & Gardening Limited | Administrative & support | 2020 |
| Assured Property and Construction Consultant and Sourcing Agent Ltd | Professional & scientific | 2008 |
| Assured Transport Services Ltd | Transport & logistics | 2022 |
| Assuredcheck Ltd | Information & communication | 2026 |
| Assuredpartners Regions Ltd | Financial services | 2003 |
| Assurefit Ltd | Manufacturing | 2025 |
| Assv Transport Limited | Transport & logistics | 2025 |
| AST Cleaning Ltd. | Administrative & support | 2015 |
| AST P.A.P.E.R. Limited | Other services | 2018 |
| AST Property Holdings Limited | Real estate | 2020 |
| AST Property Solutions Limited | Real estate | 2014 |
| AST Salvage & Parts Ltd | Wholesale & retail | 2023 |
| Asta Court Management Limited | Households | 2006 |
| Asta ERA Ltd | Financial services | 2023 |
| Astar Luxury Living Ltd | Real estate | 2023 |
| Astar Waste Limited | Water & waste | 2013 |
| Astardigm Ltd | Information & communication | 2026 |
| Astella & Co Limited | Wholesale & retail | 2020 |
| Aster & RHO Labs Ltd | Wholesale & retail | 2026 |
| Aster Mental Health CIC | Hospitality | 2021 |
| Asterin Leadership Ltd | Professional & scientific | 2023 |
| Asterios Live Ltd | Other services | 2023 |
| Asterisk Maintenance Limited | Construction | 2014 |
| Asthan Babe KE CIC | Administrative & support | 2022 |
| Asthesis Ltd | Professional & scientific | 2025 |
| Asthetiq UK Ltd | Wholesale & retail | 2026 |
| Astile Equestrian Ltd | Wholesale & retail | 2018 |
| Astin IT Solutions Ltd | Information & communication | 2023 |
| Astir Care Limited | Wholesale & retail | 2015 |
| Astle & Styl Limited | Administrative & support | 2015 |
| Astleistkonig Ltd | Real estate | 2015 |