| Apple Office Equipment Limited | Administrative & support | 1993 |
| Apple Tree Care Limited | Health & social care | 2015 |
| Appleby & Lewis Limited | Administrative & support | 2010 |
| Applemoon Interiors (Rustington) Ltd | Manufacturing | 2018 |
| Appleridge Consultancy Ltd | Professional & scientific | 2022 |
| Appleton Signs Holdings Limited | Financial services | 2024 |
| Appleton Signs Manufacturing Limited | Manufacturing | 2003 |
| Appleton Signs Unlimited | Extraterritorial | 1979 |
| Appleton's Home Improvements Limited | Construction | 2013 |
| Appliance Trader Limited | Wholesale & retail | 2002 |
| Appsynth Ltd | Information & communication | 2010 |
| Apptility Limited | Information & communication | 2013 |
| Appui Management Ltd | Wholesale & retail | 2015 |
| APT Communications Limited | Information & communication | 2024 |
| Aqua Bathrooms Installations Ltd | Construction | 2002 |
| Aqua Bathrooms Limited | Construction | 2011 |
| Aqua Cooling Hire Ltd | Extraterritorial | 2018 |
| Aqua Cooling Limited | Wholesale & retail | 2021 |
| Aqua Cooling Services Limited | Extraterritorial | 2006 |
| Aqua Cooling Solutions Holdings Limited | Administrative & support | 2021 |
| Aqua Cooling Solutions Limited | Administrative & support | 2000 |
| Aqua Pure Windows Ltd | Construction | 2025 |
| Aqua-Blue Limited | Households | 1975 |
| Aquaclear Limited | Administrative & support | 2016 |
| Aquaellia Care Limited | Health & social care | 2017 |
| Aquarian Productions Limited | Information & communication | 2001 |
| Aquark Technologies Limited | Professional & scientific | 2020 |
| Aquavirtus Ltd | Professional & scientific | 2026 |
| Aquavitrum Ltd | Manufacturing | 2012 |
| Aquora PVT Ltd | Wholesale & retail | 2026 |
| Ar-Risala LLP | | 2023 |
| Aragi Limited | Health & social care | 2026 |
| Aran Fire Protection Limited | Public administration | 2012 |
| Arbexcellence Limited | Professional & scientific | 2014 |
| Arbor Call Ltd | Administrative & support | 2013 |
| ARC Optical Limited | Professional & scientific | 2002 |
| Archer Assets UK Limited | Professional & scientific | 2007 |
| Archer Consulting Limited | Professional & scientific | 2025 |
| Archer Well Company International Limited | Mining & quarrying | 2015 |
| Archers Gate Local Centre Management Company Limited | Households | 2011 |
| Archers Way Management Company Limited | Households | 2015 |
| Archetype Capital Management Limited | Administrative & support | 2010 |
| Architectural Energy Solutions Limited | Professional & scientific | 2021 |
| Arcprotect Limited | Construction | 2022 |
| Ardent Kitchens Limited | Manufacturing | 2016 |
| Ardtully Limited | Manufacturing | 2014 |
| Ares Legal Limited | Professional & scientific | 2024 |
| Argo Health and Safety Limited | Professional & scientific | 2026 |
| Argot Bertha Productions Ltd | Information & communication | 2016 |
| ARH Tiling & Bathrooms Ltd | Construction | 2023 |
| Arizona Hair Limited | Other services | 2017 |
| ARK Groundworks Ltd | Other services | 2017 |
| Arkaya Elite Estates Ltd | Real estate | 2025 |
| Arkaya Venture Limited | Information & communication | 2014 |
| Arlington Fleet Group Limited | Professional & scientific | 2011 |
| Arlington Fleet Services Limited | Professional & scientific | 2003 |
| Arlington Rail Services Limited | Transport & logistics | 2001 |
| Armistice Studios Ltd | Information & communication | 2021 |
| Armour Security (London) Limited | Administrative & support | 1983 |
| Armoured Electrical & Building Ltd | Construction | 2020 |
| Arora Commercials Ltd | Wholesale & retail | 2021 |
| Arora Properties Investment Ltd | Real estate | 2018 |
| Aros Marine Ltd | Manufacturing | 2024 |
| Arran Accounting Ltd | Professional & scientific | 2001 |
| Arrow Electrical Solutions Limited | Construction | 2025 |
| Art IS Therapy Ltd | Other services | 2018 |
| Art-B Property Developments Ltd | Real estate | 2024 |
| Artel Automation Ltd | Professional & scientific | 2021 |
| Arun Group Holdings Limited | Financial services | 2026 |
| Arundel Fire Security and Electrical Limited | Construction | 2011 |
| Arvinder's Taxi Ltd | Transport & logistics | 2024 |
| AS the Trend Goes Ltd | Professional & scientific | 2017 |
| ASC Carpentry Limited | Construction | 2011 |
| ASCENDREMOVALS.N808 Ltd | Transport & logistics | 2026 |
| Ascent Stud Limited | Agriculture & fishing | 2025 |
| Asgaris LLP | | 2022 |
| ASH Track Ltd | Professional & scientific | 2021 |
| Asha Consulting Services Ltd | Information & communication | 2019 |
| Ashby Fields Management Company Limited | Households | 1996 |
| Ashdell Storage Ltd | Transport & logistics | 2025 |
| Ashdent Healthcare Limited | Health & social care | 2013 |
| Ashlawn Gardens Limited | Real estate | 1988 |
| Ashlett Construction Limited | Construction | 2012 |
| Ashore Project Management Ltd | Construction | 2015 |
| Ashplan Design Limited | Professional & scientific | 2026 |
| Ashton Nine Ltd | Real estate | 2021 |
| Ashwest Group Ltd | Professional & scientific | 2018 |
| Ashwood Place (Winchester) Management Company Limited | Real estate | 2010 |
| Aspect (Eastleigh) Limited | Professional & scientific | 2016 |
| Aspect Building Communities Limited | Professional & scientific | 2014 |
| Aspect Home Improvements South Limited | Construction | 2015 |
| Aspect Intergrated Care Limited | Public administration | 2018 |
| Aspen & ASH Limited | Manufacturing | 2014 |
| Aspen Plumbing and Heating Limited | Construction | 2016 |
| Aspire 38 Limited | Real estate | 2016 |
| Aspire Law LLP | | 2014 |
| Asset Management (2025) Limited | Financial services | 2024 |
| Assets and Equity Limited | Real estate | 2016 |
| Associated Property Developments Limited | Real estate | 1993 |
| Aston Nicholas Limited | Real estate | 2019 |