| APL Techs Ltd | Transport & logistics | 2026 |
| Apogee Procurement Limited | Professional & scientific | 2018 |
| Apollo Estates Limited | Real estate | 1998 |
| Appcourt Limited | Health & social care | 1996 |
| Appdec UK Limited | Information & communication | 2009 |
| Apple Group Limited | Financial services | 2019 |
| Apple PIE Property Ltd | Real estate | 2024 |
| Apple Travel Ltd | Transport & logistics | 2007 |
| Apple Yard Developments Ltd | Real estate | 2021 |
| Appleby Shaw Limited | Professional & scientific | 2010 |
| Appybrand Ltd | Manufacturing | 2026 |
| Aptania Ltd | Other services | 2015 |
| Aquascend Ltd | Other services | 2021 |
| Aquro Limited | Professional & scientific | 2025 |
| AR Group Investment Limited | Real estate | 2020 |
| AR Venz Componentes Industriales Ltd | Extraterritorial | 2010 |
| Aragorn Groupe Limited | Information & communication | 2013 |
| Arborfield Close Residents (Thirty SIX) Limited | Households | 1976 |
| Arborfield Consulting Limited | Professional & scientific | 2014 |
| Arcadia Corporate Merchandise Limited | Professional & scientific | 1997 |
| Arcadia Corporate Services Ltd | Other services | 2014 |
| Archangel Consulting Group Ltd | Professional & scientific | 2024 |
| Archer Search & Selection Limited | Administrative & support | 2017 |
| Arches Training Limited | Other services | 2017 |
| Archie C Ltd | Arts & recreation | 2025 |
| Archimedes Business Consulting Limited | Information & communication | 2010 |
| Arden Cargo International Limited | Transport & logistics | 2026 |
| Ardnamara Services Ltd | Information & communication | 2009 |
| Ardric Limited | Real estate | 2026 |
| Area Europe Limited | Construction | 2018 |
| Area GBR Limited | Construction | 2018 |
| Area Property Development Limited | Real estate | 2017 |
| Area SQ. Limited | Construction | 1999 |
| Arema Limited | Professional & scientific | 1999 |
| Argentum Diagnostics Limited | Health & social care | 2025 |
| Argex UK & IRL Limited | Wholesale & retail | 2015 |
| ARI Construction Ltd | Construction | 2015 |
| Aries Concierge Limited | Other services | 2022 |
| Arina Studio Ltd | Information & communication | 2016 |
| Arissie Limited | Real estate | 2019 |
| Arnav Consulting Services Limited | Administrative & support | 2014 |
| Aromatic Systems Limited | Other services | 2006 |
| Arraa Investments Limited | Real estate | 2022 |
| Arsal Technologies Limited | Information & communication | 2013 |
| Art Beyond Belief Limited | Health & social care | 2008 |
| Artafrique Limited | Wholesale & retail | 1989 |
| Arthur Holdings Ltd | Real estate | 2023 |
| Arthur Road Investments Limited | Real estate | 2024 |
| Artichoke Architectural Consultancy Limited | Professional & scientific | 2012 |
| Artifex Technologies Ltd | Information & communication | 2025 |
| Artis Gear Ltd | Manufacturing | 2025 |
| Artisan Design and Build (Surrey) Ltd | Construction | 2022 |
| Artisan MM Limited | Information & communication | 2013 |
| Artisan Plumbing and Heating (Surrey) Limited | Construction | 2025 |
| Arundale Consulting Limited | Professional & scientific | 2005 |
| Arundel Court Residents' Association (Slough) Limited | Households | 1971 |
| AS Property OPS Ltd | Real estate | 2022 |
| AS2 Construction Ltd | Construction | 2019 |
| AS2 Developments Ltd | Construction | 2021 |
| AS2 Group Ltd | Construction | 2021 |
| Asante & Co Solutions Limited | Hospitality | 2018 |
| Asat Masters Ltd | Professional & scientific | 2025 |
| Asbestos 2GO Limited | Construction | 2012 |
| Ascentia Law Ltd | Professional & scientific | 2018 |
| Asclepius TS Limited | Information & communication | 2016 |
| Ascot Corner Freehold Limited | Households | 2019 |
| Ascot Corner Management Company Limited | Households | 2015 |
| Ascot Gate Automation Ltd | Administrative & support | 2019 |
| Ascot Law Limited | Professional & scientific | 2023 |
| Ascot Promotions Limited | Administrative & support | 2004 |
| Ascot Storage Limited | Real estate | 2020 |
| Ascot Surgical Limited | Health & social care | 2025 |
| Ascots Lettings Limited | Households | 2019 |
| ASH & Knight Ltd | Wholesale & retail | 2025 |
| Asha Properties (UK) Ltd | Real estate | 2006 |
| Ashburn Property Consultants Limited | Real estate | 2013 |
| Ashdrive Limited | Professional & scientific | 1992 |
| Ashwell and Morden Garden Town Limited | Construction | 2025 |
| Ashwood Court Freehold Company Limited | Households | 2011 |
| Asia Business Marketing Ltd | Professional & scientific | 2023 |
| Asia Pacific Holdings Limited | Administrative & support | 2000 |
| Askew-Peace Properties Limited | Real estate | 2018 |
| Aslan Cafe & Bistro Limited | Hospitality | 2021 |
| Aspects Architectural Services Ltd. | Professional & scientific | 2012 |
| Aspen Capital Group Limited | Financial services | 2000 |
| Aspen Property Services Limited | Financial services | 1999 |
| Aspire Business Consultancy Limited | Administrative & support | 2020 |
| Aspire Food Wholesale Ltd | Wholesale & retail | 2025 |
| Assess Limited | Manufacturing | 2025 |
| Assist Investigations Ltd | Administrative & support | 2024 |
| AST Professional Consulting Limited | Professional & scientific | 2010 |
| Aster Travel & Concierge Services Limited | Professional & scientific | 2026 |
| Asteri Services Limited | Health & social care | 2021 |
| Aston Bridge Motors Ltd | Wholesale & retail | 2025 |
| Aston Shore Ltd | Professional & scientific | 2023 |
| Astra Imprints Design Ltd | Professional & scientific | 2023 |
| Astraia Digital Ltd | Professional & scientific | 2024 |
| Astro Project Limited | Real estate | 2001 |
| AT Eco Ltd | Agriculture & fishing | 2022 |
| AT Stone Construction Ltd | Construction | 2021 |