| Aran Advisory Services Limited | Professional & scientific | 2023 |
| Arav Commercials Ltd | Real estate | 2016 |
| Arax Ltd | Transport & logistics | 2011 |
| ARC Integration Ltd | Administrative & support | 2022 |
| Arcadian Prestige Estates Limited | Real estate | 2025 |
| Arcadian Restoration Limited | Construction | 2015 |
| Arch Logistics & Training Group Limited | Transport & logistics | 2022 |
| Arch Logistics Vehicle Hire Limited | Administrative & support | 2025 |
| Archer Security Ltd | Administrative & support | 2018 |
| Archers Autos Ltd | Wholesale & retail | 2025 |
| Archital Coatings Limited | Manufacturing | 2025 |
| Archital Fabrications Limited | Manufacturing | 2023 |
| Archital Holdings Limited | Financial services | 2022 |
| Architectural Window Tinting Limited | Extraterritorial | 2023 |
| Archstone Group Ltd | Administrative & support | 2025 |
| Arcox Landscaping Ltd | Administrative & support | 2020 |
| Arcs Retail Ltd | Wholesale & retail | 2023 |
| Ardudwy Distillery Ltd | Extraterritorial | 2015 |
| Arek Care Consulting Ltd | Health & social care | 2020 |
| Arena Conservatories Ltd | Construction | 2005 |
| Ares Garage Limited | Wholesale & retail | 2026 |
| Argent Flow Trade Limited | Wholesale & retail | 2026 |
| ARI Kalare Ltd | Hospitality | 2020 |
| Aribas Property Ltd | Real estate | 2025 |
| Aricer Limited | Information & communication | 2009 |
| Arjw Developments Ltd | Construction | 2023 |
| Arkeda Transport Ltd | Transport & logistics | 2023 |
| Arkh Properties Limited | Real estate | 2024 |
| Arkive Ltd | Information & communication | 2025 |
| Arleston Manor Drive Limited | Households | 2010 |
| Arleston Manor Management Limited | Households | 2009 |
| Arme Services Ltd | Other services | 2023 |
| Armp Ltd | Professional & scientific | 2023 |
| Arnie's Transport Ltd | Transport & logistics | 2025 |
| Arnold Medicals UK Ltd | Information & communication | 2019 |
| Arnold Squared Limited | Real estate | 2022 |
| ARP Property Estates Limited | Real estate | 2024 |
| Arrc IT Solutions Limited | Information & communication | 2022 |
| Arrc Solutions Limited | Real estate | 2016 |
| Arrling Limited | Manufacturing | 2010 |
| Arrling Services Limited | Professional & scientific | 2019 |
| Arrobe Property Ltd | Real estate | 2025 |
| Arrow Civils Ltd | Construction | 2023 |
| Arrow Transport Services Limited | Transport & logistics | 2016 |
| Arthur Salles Ltd | Construction | 2026 |
| Artisan Kitchens and Bathrooms Ltd | Construction | 2023 |
| Artisan Roofing (2026) Limited | Construction | 2026 |
| Artizan Ltd | Construction | 2025 |
| Artpit Ltd | Other services | 2020 |
| Artteria Engineering Services Ltd | Wholesale & retail | 2013 |
| Arty Bars Ltd | Hospitality | 2007 |
| Arvaris Ltd | Other services | 2020 |
| Arwyn Jones Limited | Wholesale & retail | 2012 |
| Aryse Logistics Limited | Transport & logistics | 2023 |
| AS 19 Ltd | Real estate | 2025 |
| AS Neale GAS Services Ltd | Administrative & support | 2014 |
| As-Siraj Education Ltd | Education | 2021 |
| ASA Mortgages Ltd | Financial services | 2024 |
| Asadi Drive Ltd | Transport & logistics | 2023 |
| Asado Restaurant Limited | Hospitality | 2016 |
| Ascot Acquisition Holdings Limited | Financial services | 2022 |
| Ascot Building Consultancy Limited | Other services | 2025 |
| Ascot Mechanical Services Ltd | Construction | 2019 |
| Aseda Consultancy Limited | Professional & scientific | 2017 |
| Asention Ltd | Administrative & support | 2018 |
| ASG (Telford) Property Limited | Real estate | 2018 |
| ASG Architects Ltd | Professional & scientific | 2015 |
| ASG Investments Limited | Financial services | 2011 |
| Asgala Ltd | Other services | 2024 |
| Ashdale Consultants Ltd | Financial services | 2025 |
| Ashdown Partners Ltd | Professional & scientific | 2011 |
| Ashford Plumbing Ltd | Manufacturing | 2016 |
| Ashley Alexander Limited | Professional & scientific | 2014 |
| Ashley Alexander Properties Limited | Real estate | 2017 |
| Ashley Commercial Vehicles Limited | Wholesale & retail | 2003 |
| Ashley Kalym Books Limited | Arts & recreation | 2013 |
| Ashton & Bentley Baths Limited | Administrative & support | 2009 |
| Ashton & Bentley Distribution Ltd | Administrative & support | 2009 |
| Asibal Ltd | Other services | 2019 |
| Asitum Ltd | Other services | 2019 |
| Asjoet Ltd | Transport & logistics | 2018 |
| ASK (Telford) Ltd | Financial services | 2016 |
| ASK Seek Knock Ltd | Information & communication | 2024 |
| Aslan Enterprise Ltd | Health & social care | 2022 |
| Aspera Ltd | Other services | 2019 |
| Aspire Pinnacle Ltd | Information & communication | 2022 |
| Assay Atelier Ltd | Manufacturing | 2026 |
| Asset Integrity Services Ltd | Professional & scientific | 2009 |
| Associated Telecom Limited | Information & communication | 1994 |
| Association for Industrial Archaeology | Education | 1977 |
| Assure Law Finance (NO.1) LLP | | 2014 |
| Assured Vehicle Rental (Holdings) Limited | Financial services | 2016 |
| Assured Vehicle Rental Ltd | Administrative & support | 2003 |
| AST Floorcoverings Ltd. | Wholesale & retail | 2000 |
| AST Holdings (UK) Limited | Real estate | 2002 |
| Asteria Global Limited | Other services | 2013 |
| Aston Bourne Limited | Other services | 2019 |
| Astons Properties Limited | Real estate | 2025 |
| Astoria Tower Development Ltd | Real estate | 2022 |
| Astosam Ltd | Other services | 2019 |