| Anumegha Consulting Services Limited | Professional & scientific | 2023 |
| ANY Colour YOU Like Ltd | Wholesale & retail | 2024 |
| AOD Property Solutions Limited | Construction | 2025 |
| AP Labs Ltd | Information & communication | 2020 |
| AP Szyja Properties Ltd | Real estate | 2024 |
| APB EA Limited | Information & communication | 2025 |
| APC Consulting Ltd | Professional & scientific | 2025 |
| Apex Oak Services Ltd | Transport & logistics | 2009 |
| Apex Partnership Builds Ltd | Construction | 2020 |
| Apex Quantity Surveying Limited | Professional & scientific | 2018 |
| Apollo Financial Ltd | Professional & scientific | 2018 |
| APR Engineering (Soulbury) Limited | Wholesale & retail | 1997 |
| APR Engineering Group Limited | Professional & scientific | 2013 |
| APR Property Counsultants Ltd | Households | 2022 |
| Aqua Pond Ltd | Administrative & support | 2023 |
| Aqua Tight Roofing Solutions Ltd | Construction | 2026 |
| Aqualantic Ltd | Construction | 2025 |
| Aquamatch Ltd | Wholesale & retail | 2019 |
| AR16PROPERTIES Limited | Real estate | 2026 |
| Arbormead House (Residents) Limited | Households | 1976 |
| Arbormead House Freehold Ltd | Households | 2011 |
| ARC Retailing Ltd | Wholesale & retail | 2015 |
| Arcade Consulting Ltd | Information & communication | 1999 |
| Arcadium Ltd | Information & communication | 2025 |
| Architects @ BHD Ltd | Professional & scientific | 2003 |
| Arganese Enterprise Limited | Wholesale & retail | 2026 |
| Aria Apartments Management Company Limited | Households | 2017 |
| Ariane Design Flight Simulation Ltd | Information & communication | 2002 |
| Ariel Tech Limited | Information & communication | 2022 |
| ARK Resin Ltd | Construction | 2026 |
| Arktech AV Ltd | Professional & scientific | 2020 |
| Arlevale Limited | Households | 1989 |
| Arley (Newton Leys) Management Company Limited | Households | 2012 |
| Army and Navy C.S.L Limited | Manufacturing | 2016 |
| Army and Navy Gunmakers Limited | Manufacturing | 2016 |
| Arnold White Estates Limited | Professional & scientific | 1937 |
| Arnold White Group Limited | Real estate | 1992 |
| ARO Care Services Ltd | Health & social care | 2025 |
| Arroma Limited | Professional & scientific | 2014 |
| Arrow Plumbing and Heating Services Ltd | Construction | 2024 |
| ARS Performance Parts Ltd | Wholesale & retail | 2024 |
| Artbox LB CIC | Education | 2026 |
| Artplus Therapeutic Services Ltd | Health & social care | 2018 |
| Artsol Ltd | Construction | 2020 |
| AS Carpentry & Joinery LLP | | 2019 |
| AS Colour UK Limited | Wholesale & retail | 2017 |
| AS Roberts Holdings Limited | Financial services | 2024 |
| Asatek (Aviation) Limited | Administrative & support | 2023 |
| Asatek Limited | Professional & scientific | 2012 |
| Ascott Farms Limited | Agriculture & fishing | 1973 |
| Ascott Nominees Limited | Extraterritorial | 1997 |
| Ascott Properties Limited | Real estate | 1995 |
| ASD Sourcing Limited | Professional & scientific | 2008 |
| ASG Risk Consultants Limited | Professional & scientific | 2014 |
| ASH Grange Residents Association Limited | Real estate | 2001 |
| ASH Grove Residents Management Company Limited | Households | 2021 |
| ASH Woodlands Limited | Agriculture & fishing | 2006 |
| Asheridge Property Limited | Real estate | 2020 |
| Ashleigh WD17 RTM Company Limited | Households | 2025 |
| Ashley Estate Freehold Company Limited | Households | 2003 |
| Ashridge Facilities Management Ltd | Extraterritorial | 2015 |
| Ashridge Group Ltd | Administrative & support | 2012 |
| Ashridge Media Limited | Professional & scientific | 2019 |
| Ashridge Security Management Ltd | Extraterritorial | 2015 |
| Ashton Grove Management Company Limited | Households | 2018 |
| ASJ Hardscapes Limited | Administrative & support | 2022 |
| Askvenkats Limited | Professional & scientific | 2024 |
| Aslan Miko Grill Ltd | Hospitality | 2025 |
| Aspekt Agency Ltd | Professional & scientific | 2021 |
| Aspire Balham Limited | Real estate | 2003 |
| Aspire Battersea Park Limited | Real estate | 2012 |
| Aspire Cuisine Ltd | Hospitality | 2012 |
| Aspire Estate Agents Limited | Administrative & support | 2020 |
| Aspire Food Ltd | Hospitality | 2018 |
| Aspire Fulham Limited | Real estate | 2003 |
| Assessment Cloud Consultancy Limited | Professional & scientific | 2020 |
| Asset Smash Ltd | Wholesale & retail | 2021 |
| Astraeus Insights Ltd | Administrative & support | 2023 |
| Astral Lake Limited | Real estate | 2017 |
| Aszent Solutions Limited | Information & communication | 2019 |
| AT Kitchens & Bathrooms Ltd | Construction | 2025 |
| Atalanta Consulting Ltd | Professional & scientific | 2023 |
| Atech Garage Equipment Services Ltd | Professional & scientific | 2019 |
| Atelia Design Ltd | Manufacturing | 2023 |
| Atkins Plumbing and Heating Ltd | Construction | 2025 |
| Atlanta Projects Ltd | Administrative & support | 2012 |
| Atlas Construction Group Ltd | Construction | 2025 |
| Atomic Trading UK Limited | Wholesale & retail | 2017 |
| Atqui Ltd | Real estate | 2010 |
| Aubergine 262 Ltd | Information & communication | 2002 |
| Audience Optimisation Ltd | Professional & scientific | 2019 |
| Audio Inertia Ltd | Information & communication | 2025 |
| Audio Mouldings Limited | Professional & scientific | 1971 |
| Augusta Florals Ltd | Wholesale & retail | 2025 |
| Aujla Records Limited | Information & communication | 2022 |
| Aumtrix Ltd | Information & communication | 2026 |
| Auna Ltd | Information & communication | 2025 |
| Auntie Annes Guildford Limited | Hospitality | 2024 |
| Aura Collagen Ltd | Wholesale & retail | 2025 |
| Aurrio Technologies Ltd | Information & communication | 2026 |