| Ashton Group Holdings Ltd | Financial services | 2022 |
| Asia Membrane Global Ltd | Construction | 2023 |
| Asium Ltd | Administrative & support | 2015 |
| ASJ Design Services Limited | Administrative & support | 2015 |
| Askyra Displays Ltd | Administrative & support | 2024 |
| Asl.Crown Ltd | Health & social care | 2026 |
| Aspects Build Ltd | Construction | 2025 |
| Aspinall Consulting Limited | Information & communication | 1998 |
| Aspire (Cherry Hinton) Management Company Limited | Households | 2012 |
| Aspire Connections C.I.C. | Health & social care | 2025 |
| Aspire Heritage Properties Ltd | Construction | 2021 |
| Aspire Taxis (Salisbury) Limited | Transport & logistics | 2017 |
| Assisi Bookkeeping Ltd | Professional & scientific | 2019 |
| Assisi Travel Limited | Transport & logistics | 2012 |
| Assist Business IT Ltd | Information & communication | 2014 |
| Assist DD Ltd | Real estate | 2012 |
| Assisted Development Limited | Construction | 2022 |
| Assurance Consultancy Ltd | Professional & scientific | 2019 |
| Aston Court (Brondesbury) Management Limited | Households | 2013 |
| Astradent (5) Limited | Health & social care | 2021 |
| Astrella Primary Stars Ltd | Education | 2019 |
| ASY PVT Ltd | Health & social care | 2023 |
| AT Seismic Consultants Ltd | Professional & scientific | 2013 |
| Atalanti TEN Limited | Administrative & support | 2005 |
| Atc-Innovation Ltd | Professional & scientific | 2009 |
| Athena Intelligence Limited | Professional & scientific | 2023 |
| Atkins Business Consulting Ltd | Professional & scientific | 2022 |
| Atkinson Bookbinders Limited | Manufacturing | 2005 |
| Atlantic Dental Limited | Health & social care | 2012 |
| Atlas Planning Group Ltd | Professional & scientific | 2017 |
| Atlas Tree Care Limited | Agriculture & fishing | 2008 |
| Atlas Venture Ltd | Real estate | 2024 |
| ATM Events Limited | Other services | 2018 |
| Atmiya Investment Limited | Real estate | 2022 |
| Atmiya News Ltd | Wholesale & retail | 2024 |
| Atmiya Retail Limited | Wholesale & retail | 2016 |
| Atper Limited | Real estate | 2013 |
| Aubrac Cattle Society of the UK Limited | Agriculture & fishing | 1990 |
| Audit for Business Development and Solutions Limited | Professional & scientific | 2025 |
| August Property Solutions Ltd | Real estate | 2023 |
| Augustine Lawrence Ltd. | Information & communication | 2017 |
| Aura Alchemy Ltd | Wholesale & retail | 2025 |
| Aurora (Portishead) Management Company Limited | Households | 2012 |
| Aurora Risk Management Ltd | Transport & logistics | 2010 |
| Ausmarine Limited | | 1965 |
| Austin Cars Ltd | Manufacturing | 2023 |
| Austin Pedal Cars Limited | Extraterritorial | 2022 |
| Authentic Style Ltd | Information & communication | 2009 |
| Auto Edition Limited | Wholesale & retail | 2020 |
| Autobahn Administration Ltd | Financial services | 2021 |
| Autocom U.K. Limited | Financial services | 1983 |
| Autofort Ltd | Transport & logistics | 2018 |
| Automargin.Co.Uk Ltd | Information & communication | 2026 |
| Automithra UK Used Carsales &Service Ltd | Wholesale & retail | 2026 |
| Automobiles Ltd | Wholesale & retail | 2026 |
| Autostrata Ltd | Wholesale & retail | 2020 |
| Autotech MOT and Repairs Limited | Wholesale & retail | 2015 |
| Autowork (Salisbury) Limited | Wholesale & retail | 2016 |
| Av&M Engineering Limited | Manufacturing | 2019 |
| Avalon (Glastonbury) Management Company Limited | Real estate | 2021 |
| Avalon Interiors Limited | Wholesale & retail | 2015 |
| Avant Garde MOT Centre Limited | Wholesale & retail | 2012 |
| Avant Health Ltd | Professional & scientific | 2021 |
| Avebury Property Ltd | Real estate | 2026 |
| Avellana Ltd | Arts & recreation | 2022 |
| Avenir Property Company Limited | Real estate | 1993 |
| Aventis Marketing Limited | Hospitality | 2012 |
| Aventra Sites Limited | Information & communication | 2026 |
| Averon Properties Ltd | Real estate | 2026 |
| Avery Recovery Ltd | Extraterritorial | 2017 |
| Aviation Investment Consultants Limited | Administrative & support | 1980 |
| Aviation Mechanical Solutions Ltd | Manufacturing | 2026 |
| Aviation Recovery Training Services Ltd | Professional & scientific | 2019 |
| Avocado Social Ltd | Professional & scientific | 2014 |
| Avon Door & Lock Company Limited | Construction | 2004 |
| Avon Farm Management Company Limited | Hospitality | 2003 |
| Avon Lettings Ltd | Real estate | 2014 |
| Avon Metals (2012) Limited | Water & waste | 2012 |
| Avon Place Management Company Limited | Households | 2007 |
| Avon Tree and Garden Services Ltd | Administrative & support | 2024 |
| Avon Valley Builders Limited | Construction | 2020 |
| Avon Valley Engineering Ltd | Manufacturing | 2006 |
| Avon Valley Holdings Limited | Professional & scientific | 2008 |
| Avon Wood (Salisbury) Limited | Administrative & support | 2018 |
| Avondale Preparatory School Limited | Education | 2013 |
| Avonflow Ltd | Real estate | 2024 |
| Avonmead Court Residents Association Limited | Households | 1981 |
| Avonstone Products Ltd | Wholesale & retail | 2003 |
| Avonvalley Community Support Ltd | Administrative & support | 2024 |
| AW General Builders Ltd | Construction | 2020 |
| Awardable Ltd | Information & communication | 2023 |
| Axcess-Electric-Bikes. Limited | Wholesale & retail | 1954 |
| Axel Dog Beds Ltd | Manufacturing | 2024 |
| Axel Dog Ltd | Manufacturing | 2024 |
| Axiom Custodian Consultancy Limited | Administrative & support | 2018 |
| Axisbridge Partners Ltd | Administrative & support | 2026 |
| Aycer Homes Developments Ltd | Construction | 2018 |
| Aycer Homes Ltd | Construction | 2018 |
| Aycer IT Solutions Limited | Information & communication | 2012 |
| Ayleswood Developments Limited | Construction | 2005 |