| Arthur Francis Accountancy Limited | Professional & scientific | 2022 |
| Arthur Joyce Contracts Limited | Construction | 2024 |
| Artificial Eden Ltd | Wholesale & retail | 2021 |
| Artisan Facilities Management Ltd | Administrative & support | 2012 |
| Artisan Svcs UK Ltd | Transport & logistics | 2026 |
| Artisserie Patisserie UK Limited | Manufacturing | 2021 |
| Artistic Curiosities Ltd | Wholesale & retail | 2024 |
| Artistry by Asia Ltd | Other services | 2025 |
| Artists Life Limited | Administrative & support | 2019 |
| Arts Fundraising Limited | Other services | 2019 |
| ARU Consultants Limited | Professional & scientific | 2019 |
| ARU Direct Limited | Education | 1999 |
| ARU Peterborough | Education | 2020 |
| Arundel Resolution Limited | Transport & logistics | 2011 |
| Arvo Properties Limited | Real estate | 2006 |
| Arvon Drain Clearing Ltd | Professional & scientific | 2013 |
| ARW Pharma Ltd | Construction | 2022 |
| Arwel Retreat Ltd | Real estate | 2025 |
| AS14 Healthcare Ltd | Health & social care | 2021 |
| Asab Limited | Health & social care | 2014 |
| Asap Health Ltd | Health & social care | 2019 |
| ASB Prop Co 2 Ltd | Real estate | 2022 |
| ASB Prop Co Ltd | Real estate | 2022 |
| Asbo Motorsport Ltd | Wholesale & retail | 2024 |
| ASC Utility Solutions Limited | Energy | 2020 |
| Ascend Broking Group Limited | Financial services | 2016 |
| Ascend Health Ltd | Financial services | 2013 |
| Ascot Consulting Medical Limited | Professional & scientific | 2008 |
| ASD Access Ltd | Information & communication | 2026 |
| Aseea Shuly Limited | Health & social care | 2023 |
| Aseelhla Medical Ltd | Health & social care | 2026 |
| Asela Tree Limited | Health & social care | 2024 |
| Asgardian Technology Ltd | Wholesale & retail | 2021 |
| Asgen Limited | Water & waste | 1999 |
| ASH Devadas Limited | Health & social care | 2025 |
| ASH Landscape & Design 2011 Limited | Administrative & support | 2011 |
| ASH1 Cars Limited | Wholesale & retail | 2024 |
| Ashamali Ltd | Real estate | 2024 |
| Ashbourne Woods Limited | Hospitality | 2013 |
| Ashca Limited | Professional & scientific | 2011 |
| Ashco Group Limited | Other services | 2024 |
| Ashcroft Facilities Ltd | Arts & recreation | 2026 |
| Ashdown Estates (Services) Limited | Real estate | 2004 |
| Ashdown Estates Limited | Professional & scientific | 1995 |
| Ashdown Property Projects Limited | Construction | 2015 |
| Ashen Ltd | Professional & scientific | 2008 |
| Ashgrove Medical Practice Limited | Health & social care | 2026 |
| Ashiani Limited | Health & social care | 2013 |
| Ashingdon Gardens (Block G) Management Company Limited | Households | 1993 |
| Ashley Property Gems Ltd | Real estate | 2024 |
| Ashley Systems Limited | Professional & scientific | 2025 |
| Ashmere Construction Ltd | Construction | 2017 |
| Ashoka Travel Limited | Hospitality | 2017 |
| Ashtec Automotive Ltd | Wholesale & retail | 2020 |
| Ashton & Charters Limited | Real estate | 2013 |
| Ashton BI Limited | Professional & scientific | 2024 |
| Ashton Charters Construction Limited | Other services | 2017 |
| Ashton Dennis Ltd | Professional & scientific | 2009 |
| Ashton LEE Building Services Ltd | Construction | 2017 |
| Ashton LEE Surveyors Personnel Limited | Professional & scientific | 2025 |
| Ashton White Estates Ltd | Real estate | 2021 |
| Ashtree Joinery (Essex) Limited | Manufacturing | 2007 |
| Ashwaste Environmental Limited | Water & waste | 2003 |
| Ashwells Sports & Country Club Limited | Arts & recreation | 1984 |
| Asia & Imran Ltd | Wholesale & retail | 2018 |
| Asign Group Ltd | Real estate | 2018 |
| ASJ Contractors Ltd | Construction | 2024 |
| Aslan Barbers(Suffolk) Ltd | Other services | 2022 |
| Aslan Coffee Limited | Hospitality | 2026 |
| Asomdwie Limited | Construction | 2016 |
| Asoy Limited | Hospitality | 2017 |
| ASP Transport Ltd | Transport & logistics | 2023 |
| Aspan Solutions Ltd | Information & communication | 2009 |
| Aspect Media Ltd | Information & communication | 2015 |
| Aspect Place Management Company Limited | Households | 2002 |
| Aspects Childcare Limited | Health & social care | 2025 |
| Aspen Carpets and Flooring Limited | Wholesale & retail | 2012 |
| Aspen Hale Private Limited | Professional & scientific | 2025 |
| Aspen Tree Childcare Ltd | Education | 2022 |
| Aspg Limited | Manufacturing | 2012 |
| Aspire Recruitment Group Ltd | Administrative & support | 2023 |
| Aspire Your Horizons Ltd | Administrative & support | 2026 |
| Aspiring Residential Homes Ltd | Real estate | 2025 |
| Aspis Technology Ltd | Information & communication | 2026 |
| Asquare AI Digital Labs Ltd | Information & communication | 2025 |
| Assemble Investments Limited | Financial services | 2026 |
| Assessmentday Ltd | Information & communication | 2010 |
| Assessmytax Ltd | Information & communication | 2026 |
| Assetro Limited | Real estate | 1963 |
| Assets for Life Ltd | Other services | 2016 |
| Assistppc Group Ltd | Professional & scientific | 2022 |
| Associated Forensic London Limited | Administrative & support | 2023 |
| Association of Telugu Christians UK & Europe Ltd | Other services | 2023 |
| Assured Connect Ltd | Administrative & support | 2022 |
| Assured Fire Safety Limited | Other services | 2005 |
| Assurelabs Ltd | Information & communication | 2023 |
| Astro Care Ltd | Administrative & support | 2020 |
| Astroid Limited | Professional & scientific | 2017 |
| Astute Software Development Limited | Information & communication | 2015 |
| Asvikaa Ltd | Hospitality | 2019 |