| Appoway Ltd | Manufacturing | 2019 |
| Approved Compliance Ltd | Construction | 2022 |
| Approved Fire Risk Assessments Ltd | Public administration | 2023 |
| APR Driveway Management Limited | Extraterritorial | 2009 |
| Apro Investments Limited | Financial services | 2023 |
| Aptimate Solutions Ltd | Information & communication | 2026 |
| Aquilo Facilities Limited | Construction | 2024 |
| AR Risk Ltd | Professional & scientific | 2019 |
| Ar-Sq Limited | Information & communication | 2023 |
| Arbortas Grounds Maintenance Services Ltd | Administrative & support | 2025 |
| ARC Office Systems Limited | Manufacturing | 2010 |
| Arcadian Architectural Services Ltd | Professional & scientific | 2006 |
| Arcadiapm Limited | Real estate | 2024 |
| Arch Media Limited | Information & communication | 2022 |
| Archer Express Limited | Other services | 2018 |
| Archernar Limited | Information & communication | 2026 |
| Archview Projects Ltd | Construction | 2016 |
| Arciso Limited | Information & communication | 2025 |
| ARD Partners Limited | Professional & scientific | 2019 |
| Ardell FM Ltd | Administrative & support | 2026 |
| Ardenrun Properties Limited | Real estate | 1996 |
| Arepahouse Ltd | Hospitality | 2021 |
| Argaman Capital LLP | | 2018 |
| Argentum Asset LLP | | 2016 |
| Arkstone Homes Limited | Real estate | 2025 |
| Armatire Limited | Administrative & support | 2016 |
| Armourcoat Holdings Limited | Financial services | 2018 |
| Armourcoat Limited | Manufacturing | 1986 |
| Armstrong Drainage & Plumbing Ltd | Water & waste | 2021 |
| Armstrong Joplin Limited | Construction | 2018 |
| Aroc Consulting Ltd | Other services | 2016 |
| Aroma Scents Limited | Health & social care | 2005 |
| Arppas LLP | | 2017 |
| Arran Advisors Ltd | Professional & scientific | 2024 |
| Arroprom Therapy Ltd. | Health & social care | 2018 |
| Arrowan Consulting Limited | Professional & scientific | 2015 |
| Arrowhead Group Limited | Professional & scientific | 1994 |
| Arsan Medical Ltd | Health & social care | 2018 |
| Art G&J Ltd | Information & communication | 2010 |
| Art Kingdom Limited | Arts & recreation | 2025 |
| Art Presentations Limited | Arts & recreation | 2010 |
| Art-Manufacture-Design (DE) Ltd. | Wholesale & retail | 2018 |
| Art-Manufacture-Design (UK) Ltd. | Wholesale & retail | 2016 |
| Art-Manufacture-Design (US) Ltd | Wholesale & retail | 2022 |
| Artemis LMS Ltd | Education | 2024 |
| Artha Vriddhi Investments Ltd | Financial services | 2024 |
| Arthur Marshall Coffee LLP | | 2018 |
| Artinsys Limited | Information & communication | 2004 |
| Artline Consultancy Limited | Wholesale & retail | 2025 |
| Arts Umbrella Limited | Professional & scientific | 1989 |
| Arty Security Ltd | Administrative & support | 2019 |
| Arun Accountancy Ltd | Professional & scientific | 2017 |
| Arvos Consulting Ltd | Wholesale & retail | 2014 |
| Asap Safety Limited | Wholesale & retail | 2020 |
| Ascendia Holdings Ltd | Professional & scientific | 2024 |
| Ascent Electrical Limited | Construction | 2025 |
| Ascoe Properties Ltd | Real estate | 2014 |
| Asee Property Ltd | Real estate | 2016 |
| ASG Cars Ltd | Transport & logistics | 2012 |
| ASH Green Grass Limited | Construction | 2016 |
| ASH Media Ltd | Information & communication | 2013 |
| ASH Recovery Limited | Transport & logistics | 2024 |
| ASH SRI Ltd | Real estate | 2024 |
| ASH Tree Drive Management Company Limited | Professional & scientific | 2002 |
| Ashbrook Vine Limited | Real estate | 2005 |
| Ashdown Driveways Surfacing Limited | Construction | 2022 |
| Ashley Rose Limited | Professional & scientific | 2007 |
| Ashton Holdings Ltd | Real estate | 2018 |
| Ashton Manor Properties Ltd | Real estate | 2016 |
| Ashton Manor Whitworth Ltd | Real estate | 2024 |
| Ashton Taylor Smith Ltd | Wholesale & retail | 2014 |
| ASI AB Limited | Real estate | 2010 |
| ASK for Pharma Solutions Limited | Health & social care | 2012 |
| ASM Classic Cars Limited | Wholesale & retail | 2021 |
| ASM Classics Limited | Wholesale & retail | 2017 |
| ASP Propserv Ltd | Administrative & support | 2016 |
| Aspden Design Limited | Professional & scientific | 2016 |
| Asset Auctions Ltd | Wholesale & retail | 2019 |
| Asset Design Studio Ltd | Arts & recreation | 2012 |
| Assured Enforcement Limited | Administrative & support | 2012 |
| Astaire Court Management Company Limited | Households | 2004 |
| Aston View Management Company Ltd | Households | 2022 |
| Astra Contracting Limited | Construction | 2003 |
| Astrolabe Advisors Ltd | Professional & scientific | 2026 |
| Astrolabe Immersive Holdings Limited | Administrative & support | 2023 |
| Ataa Limited | Financial services | 1997 |
| Atanda Design Ltd | Professional & scientific | 2025 |
| Atelier Rousseau Ltd | Wholesale & retail | 2009 |
| Atlam Properties Limited | Real estate | 2017 |
| Atlantic Arbitrage Ltd | Financial services | 2025 |
| Atlas Intelligence Group Limited | Information & communication | 2026 |
| Atlas Production Music Limited | Information & communication | 2002 |
| Atlas UK Homes Ltd | Real estate | 2026 |
| Atlasica Ltd | Information & communication | 2023 |
| Atman Clinic Limited | Health & social care | 2012 |
| Atman Retail Ltd | Other services | 2013 |
| Aublet Limited | Professional & scientific | 2017 |
| Auction Web Ltd | Information & communication | 2020 |
| Auctus Advisors LLP | | 2019 |
| Auden Limited | Wholesale & retail | 2025 |