| AR Engineering Limited | Professional & scientific | 2025 |
| Ar-Cb Developments Ltd | Real estate | 2025 |
| Aram Holdings Limited | Wholesale & retail | 2025 |
| Aramuk Ltd | Wholesale & retail | 2025 |
| Arberi Coffee Limited | Hospitality | 2017 |
| ARC Design & Development Limited | Professional & scientific | 2010 |
| ARC Plastics Limited | Administrative & support | 2019 |
| ARC Polymers Ltd | Manufacturing | 2023 |
| Arca Baby Ltd | Wholesale & retail | 2024 |
| Arcapix Holdings Limited | Administrative & support | 2013 |
| Arcastream Ltd | Administrative & support | 2013 |
| Arch Golf Limited | Education | 2025 |
| Architectural & Style Ltd | Construction | 2018 |
| Arcsecond Limited | Arts & recreation | 2024 |
| Ardelmers Management Company Limited | Households | 1974 |
| Ardentity Limited | Professional & scientific | 2021 |
| Ardeo Limited | Information & communication | 1995 |
| Ardex Advisory Ltd | Professional & scientific | 2025 |
| Ardmem Consultancy Services Ltd | Information & communication | 2021 |
| Ardour Education Limited | Education | 2024 |
| Arel Lighting Ltd | Manufacturing | 2024 |
| Arena Software Limited | Information & communication | 2013 |
| Arete Poolingco Limited | Financial services | 2025 |
| Argostoli Enterprises Limited | Other services | 1999 |
| Argyll Metals Limited | Mining & quarrying | 2022 |
| Arhion Investments Limited | Real estate | 1975 |
| Aris International Lawyers Ltd | Professional & scientific | 2017 |
| Arizona Apartments Limited | Administrative & support | 1999 |
| Arjco Enterprise Ltd | Real estate | 2023 |
| ARK Strategic Services Limited | Professional & scientific | 2013 |
| Arkafy Ltd | Information & communication | 2020 |
| Arktiaskog Infotech Consult Limited | Information & communication | 2025 |
| Arlington Court Residents Association Limited | Households | 1990 |
| Arlo Fades Limited | Other services | 2025 |
| Arma Gungor Limited | Real estate | 2022 |
| Armour Contractors Investments Limited | Administrative & support | 2024 |
| Armour Contractors Ltd | Administrative & support | 2010 |
| Arnmore Limited | Administrative & support | 2017 |
| Arnott’S Foods UK Ltd | Wholesale & retail | 2019 |
| Arqueline Limited | Professional & scientific | 2020 |
| Arrian Limited | Professional & scientific | 2021 |
| Arrio Infra Limited | Real estate | 2026 |
| Arshad Traders Ltd | Wholesale & retail | 2020 |
| Art for Art's Sake Limited | Professional & scientific | 2014 |
| Art Robotics Ltd | Manufacturing | 2023 |
| Artemis Capital Group Ltd | Real estate | 2019 |
| Artesian (UK) Limited | Other services | 2003 |
| Artesian Capital Management (UK) LLP | | 2004 |
| Artex ILS Services UK Ltd | Financial services | 2017 |
| Artfactory Production Limited | Administrative & support | 2017 |
| Artificial Horizon Productions Limited | Information & communication | 2004 |
| Artistic Licence Universal Limited | Professional & scientific | 2024 |
| Artizan Catering UK Ltd | Administrative & support | 2023 |
| Artsome Ltd | Wholesale & retail | 2022 |
| Artykid Ltd | Administrative & support | 2024 |
| Arvores Limited | Professional & scientific | 2007 |
| Arwah Trading Ltd | Wholesale & retail | 2025 |
| ARZ Investment Limited | Real estate | 2023 |
| AS Bespoke Carpentry Limited | Construction | 2023 |
| AS Buy to LET Ltd | Real estate | 2026 |
| AS Foods Limited | Wholesale & retail | 2012 |
| AS Real Estate Ltd | Real estate | 2021 |
| Asana Health Limited | Other services | 2011 |
| Asankheya Capital Ltd | Real estate | 2026 |
| Ascension Real Estate Ltd | Real estate | 2021 |
| Ases Holdings Ltd | Financial services | 2024 |
| Ashburnham Investment Management Ltd | Professional & scientific | 2013 |
| Asheborough House Care Centre Ltd | Health & social care | 2022 |
| Ashok Thapper Builders Ltd | Construction | 2017 |
| Ashton Homes Limited | Real estate | 2021 |
| Ashville Health Care Ltd | Health & social care | 2014 |
| Ashville Residential Home Ltd | Health & social care | 2012 |
| Asis Fast Service Ltd | Construction | 2025 |
| ASJ Flexi Consultants Ltd | Professional & scientific | 2024 |
| ASJ Management Consultant Limited | Professional & scientific | 2022 |
| Asnp Limited | Health & social care | 2011 |
| Asomani Ltd | Construction | 2022 |
| Aspen Financial Services Limited | Financial services | 2006 |
| Aspen Lodge Care Ltd | Health & social care | 2023 |
| Aspera London Ltd | Construction | 2014 |
| Aspire Compulsory Purchase Limited | Administrative & support | 2016 |
| Aspire IT Consulting Limited | Information & communication | 2014 |
| Aspire Tutorials Ltd | Education | 2024 |
| ASQ Branding Ltd | Professional & scientific | 2024 |
| ASR Trade Ltd | Wholesale & retail | 2023 |
| Asset and Investment Management Limited | Other services | 1989 |
| Assetq Limited | Information & communication | 2012 |
| Assetsure Surveying Ltd | Professional & scientific | 2026 |
| Assi Contracting and Engineering Limited | Construction | 2026 |
| Association of Catering Excellence Ltd | Other services | 2005 |
| Assos Property Trading Ltd | Real estate | 2021 |
| Assura Living Ltd | Wholesale & retail | 2026 |
| Aster Associates Limited | Professional & scientific | 2012 |
| Aster Catering Ltd | Manufacturing | 2023 |
| Asterwillow Limited Partnership | | 2022 |
| Astir Cigars & Wine Ltd | Wholesale & retail | 2016 |
| Astor Close Management Limited | Households | 1966 |
| AT Pace Consulting Limited | Professional & scientific | 2012 |
| Ataya Barber Ltd | Other services | 2020 |
| Atelier Daba Limited | Professional & scientific | 2020 |