| Argentis Financial Planning Ltd | Financial services | 2008 |
| Argentis Group Ltd | Financial services | 2003 |
| Argentis Wealth Management Ltd | Financial services | 2001 |
| Argerdh Limited | Information & communication | 2017 |
| Argo MRT Ltd | Manufacturing | 2025 |
| Arioch Consulting Limited | Professional & scientific | 2006 |
| Arjay Plumbing Limited | Extraterritorial | 2016 |
| ARL Homes Ltd | Real estate | 2024 |
| ARL Renovations Ltd | Real estate | 2018 |
| Arlia Limited | Education | 2009 |
| Armashield Limited | Extraterritorial | 2016 |
| Armorpax Ltd | Manufacturing | 2021 |
| Armsgate Property Sourcing Ltd | Real estate | 2020 |
| Arnold Facilities Ltd | Transport & logistics | 2017 |
| Arnold Powered Access Ltd | Manufacturing | 2020 |
| Arnside Industrial Solutions Limited | Professional & scientific | 2011 |
| Arogyata Ltd | Hospitality | 2018 |
| Arrington Limited | Real estate | 1994 |
| Arrive in Style Portsmouth Limited | Transport & logistics | 2007 |
| Arrowsmith Research and Analysis Ltd | Professional & scientific | 2025 |
| Arte Support Solutions Limited | Professional & scientific | 2023 |
| Arthur Grosvenor & Co Limited | Information & communication | 2015 |
| Artianic Limited | Professional & scientific | 2024 |
| Artifex Building Limited | Construction | 2022 |
| Artifex Limited | Construction | 1984 |
| Artisan Carpenters Ltd | Construction | 2016 |
| Artizans of Wood Ltd | Manufacturing | 2013 |
| Artkive Limited | Wholesale & retail | 2024 |
| Artlux Media Ltd | Professional & scientific | 2024 |
| Arts Gone MAD Limited | Arts & recreation | 2024 |
| Arts Property Management Limited | Real estate | 2023 |
| ASA 28 Civils & Groundworks Ltd | Construction | 2023 |
| Asatuda Ltd. | Information & communication | 2018 |
| ASC Training & Consultancy Ltd | Public administration | 2025 |
| Ascent Consultancy Team Limited | Professional & scientific | 2008 |
| ASH LAB Ltd | Professional & scientific | 2026 |
| Ashbourne Developments and Construction Limited | Real estate | 2023 |
| Ashbourne Freeholds Limited | Real estate | 2021 |
| Ashby RD Hinckley Ltd | Real estate | 2018 |
| Ashco Properties Limited | Real estate | 2021 |
| Ashcroft Court (Petersfield) Limited | Households | 1971 |
| Ashlake Estates Limited | Administrative & support | 2010 |
| Ashlake Homes Limited | Financial services | 2014 |
| Ashley Fine Frames Limited | Professional & scientific | 2019 |
| Ashley Haddington Ltd | Wholesale & retail | 2025 |
| Ashman Ceramics Ltd | Construction | 2022 |
| Ashridge Finance Limited | Financial services | 2015 |
| Ashtead Software Workshops Limited | Information & communication | 2004 |
| Asian Tranquil Touch Wellness Ltd | Health & social care | 2026 |
| Asiye Limited | Hospitality | 2024 |
| Askews Southsea Ltd | Hospitality | 2025 |
| Asphalt South Coast Ltd | Construction | 2019 |
| Aspire Corp Ltd | Administrative & support | 2025 |
| Aspire North West Limited | Financial services | 2024 |
| Aspire Rental Properties Ltd | Real estate | 2021 |
| Aspire Roofing Limited | Construction | 2013 |
| ASQUARED2 Limited | Construction | 2023 |
| Associated Business Solutions Ltd | Other services | 2012 |
| Association of Lymphoedema Practitioners | Other services | 2026 |
| Assured Works Direct Limited | Transport & logistics | 2016 |
| Astar-Tech Limited | Information & communication | 2025 |
| ASTAREDUCATION22 Ltd | Education | 2025 |
| Aster Capitals Ltd | Administrative & support | 2025 |
| Astlebrook Legal Limited | Professional & scientific | 2009 |
| Astlebrook Property Ventures Ltd | Construction | 2024 |
| Astra Commercial Enterprise (Ace) Ltd | Construction | 2016 |
| Astra Recycling Limited | Water & waste | 2013 |
| Astro Engineering Limited | Manufacturing | 2024 |
| Astute Mortgages Ltd | Financial services | 2020 |
| Astute Sales & Lettings Ltd | Real estate | 2024 |
| AT Scaffolding Services Ltd | Construction | 2017 |
| AT the Barn Fitness Limited | Arts & recreation | 2025 |
| ATELIER45 Limited | Professional & scientific | 2024 |
| Athena Accounting Ltd | Professional & scientific | 2021 |
| Athena Support Services Ltd | Real estate | 2023 |
| Athenapa Ltd | Administrative & support | 2019 |
| Athenova Consult Ltd. | Manufacturing | 2020 |
| Athletesiq Ltd | Education | 2024 |
| Athos Services Limited | Transport & logistics | 2008 |
| ATL General Builders Ltd | Construction | 2011 |
| ATL Hospitality and Events Ltd | Hospitality | 2023 |
| Atlantic Speaker Bureau Ltd | Extraterritorial | 2013 |
| Atlantic Yachting Limited | Transport & logistics | 2023 |
| Atlantio Limited | Information & communication | 2025 |
| Atlas Commercial Limited | Construction | 2014 |
| Atomic Construction & Landscaping Ltd | Construction | 2024 |
| Attis Engineering Solutions Ltd | Professional & scientific | 2015 |
| Attrell Tree Surgery Limited | Agriculture & fishing | 2014 |
| Atwo Properties Ltd | Real estate | 2025 |
| Aubrey J Madgwick Groundworks Limited | Construction | 2010 |
| Audionixx Limited | Information & communication | 2022 |
| Augustus Plumpkin Limited | Real estate | 1999 |
| Aura (GAS) Holdings Limited | Financial services | 2021 |
| Aura Property (South) Limited | Real estate | 2021 |
| Aura Retrofit Limited | Construction | 2007 |
| Aurelian Holdings Group Limited | Construction | 2026 |
| Authentic Smoke Ltd | Hospitality | 2025 |
| Auto Communications & Tracking Limited | Information & communication | 2013 |
| Auto-Barn Motor Services Limited | Wholesale & retail | 2010 |
| Auto-Barn Rent a Ramp Ltd | Administrative & support | 2018 |