| ANN ROY Ltd | Health & social care | 2024 |
| Anna Clark Studio Ltd | Other services | 2023 |
| Anna Wholesales Ltd | Wholesale & retail | 2025 |
| Annonay Investments Ltd | Real estate | 2025 |
| Anogon Investments Limited | Real estate | 2018 |
| Another World Trading Group Limited | Extraterritorial | 2020 |
| Another World Trading UK Limited | Wholesale & retail | 2014 |
| Anthony Stanton Limited | Administrative & support | 2002 |
| Antimas Cleaning Ltd | Professional & scientific | 2014 |
| Antwi Medical Services Limited | Health & social care | 2026 |
| Antz Builders Ltd | Construction | 2016 |
| AOP Healthcare Ltd | Health & social care | 2026 |
| AP Enterprise Holding Ltd | Financial services | 2020 |
| Apache Business Services Limited | Information & communication | 2005 |
| Apex Brickcutters (Midlands) Limited | Manufacturing | 2009 |
| Apex Carpentry Services Limited | Construction | 1998 |
| Apex Plant Research Limited | Professional & scientific | 2017 |
| Apex Refrigeration Installation Ltd | Construction | 2024 |
| Apex Underfloor Heating Ltd | Wholesale & retail | 2021 |
| Aphelion Games Ltd | Manufacturing | 2023 |
| Apini Therapeutics Limited | Professional & scientific | 2021 |
| APJ Retail Ltd | Wholesale & retail | 2024 |
| APM Window Cleaning Limited | Administrative & support | 2015 |
| App Hub Ltd | Information & communication | 2018 |
| App Stores Ltd | Wholesale & retail | 2019 |
| Apps (UK) Limited | Professional & scientific | 2007 |
| APT Property Consultancy Ltd | Administrative & support | 2025 |
| Aqua Environmental Maintenance Ltd | Water & waste | 2018 |
| Aqua Environmental Systems Limited | Water & waste | 2011 |
| Aquamaster Water Treatment Ltd. | Administrative & support | 2011 |
| Aquamatrix Ltd | Wholesale & retail | 2021 |
| Ara-Transport Ltd | Transport & logistics | 2019 |
| Aragon Place Ltd | Real estate | 2023 |
| Aranac Consulting Limited | Information & communication | 2025 |
| Aravis Business Growth Limited | Professional & scientific | 2018 |
| Arbam Consulting Limited | Information & communication | 2020 |
| Arbitrary Ltd | Professional & scientific | 2007 |
| ARC Accomodations Limited | Real estate | 2020 |
| Arcade Car Services Limited | Wholesale & retail | 2024 |
| Arcadia Cloud Ltd | Information & communication | 2019 |
| Arcale Limited | Professional & scientific | 1997 |
| Arch Motor & Manufacturing Co. Limited | Manufacturing | 1962 |
| Archangel Accounting Limited | Professional & scientific | 2007 |
| Arcondo Limited | Professional & scientific | 2022 |
| Ardent Loft Solutions Ltd | Construction | 2025 |
| ARK and General Limited | Extraterritorial | 1989 |
| Arrestapest (Gidding) Limited | Administrative & support | 1996 |
| Arrodare Limited | Transport & logistics | 2022 |
| Arrvic Holdings Limited | Financial services | 2023 |
| Arrvic Properties Ltd | Real estate | 2020 |
| Art 2 Rent Limited | Extraterritorial | 2007 |
| Art Welding Services Ltd | Construction | 2016 |
| Arthur's Services Ltd | Transport & logistics | 2012 |
| Artifex Conservation Limited | Professional & scientific | 2016 |
| Artisan Florist English Petal and Herb Ltd | Wholesale & retail | 2018 |
| ARW Restorations Ltd | Wholesale & retail | 2025 |
| AS Keen AS Mustard Ltd | Arts & recreation | 2022 |
| Asbestos Control Management Ltd | Professional & scientific | 2025 |
| Ascent Property Ltd | Real estate | 2020 |
| ASH Elements Limited | Education | 2020 |
| ASH Professional Services Limited | Professional & scientific | 2017 |
| ASH Tree Property Services Ltd | Other services | 2026 |
| Ashby Homes Limited | Construction | 1999 |
| Ashden Limited | Professional & scientific | 2020 |
| Ashmire Leisure Ltd | Hospitality | 2021 |
| Ashwood Gardens Property Management Company NO 1 Limited | Households | 2004 |
| Asiasetup Limited | Professional & scientific | 2000 |
| ASK IT Services Limited | Information & communication | 2002 |
| Asla Ltd | Administrative & support | 1991 |
| Asla Travel Ltd | Professional & scientific | 2001 |
| ASM Brooklands Limited | Health & social care | 2012 |
| Aspen Payments Limited | Wholesale & retail | 2007 |
| Aspire Social Care Services Ltd | Health & social care | 2023 |
| Asppen Ltd | Real estate | 2024 |
| Assert Consultants Ltd | Information & communication | 2019 |
| Assetbridge Investments Ltd | Real estate | 2026 |
| ASSIST2 Ltd | Administrative & support | 2015 |
| Asso Ltd | Wholesale & retail | 2017 |
| Associate Consultants Limited | Construction | 2003 |
| Association of Specialist Underpinning Contractors | Other services | 1992 |
| Assured Biosolids Limited | Other services | 2015 |
| Astflick Group Limited | Wholesale & retail | 2006 |
| Astflick Holdings Ltd | Financial services | 2025 |
| Aston Pharma Limited | Extraterritorial | 2014 |
| Aston Work Wear Limited | Wholesale & retail | 2015 |
| Astraltis & Co. Ltd | Transport & logistics | 2025 |
| Atlas Consulting Hseq Ltd | Professional & scientific | 2022 |
| Atlas Equipment Limited | Administrative & support | 2017 |
| Atnet Software Limited | Information & communication | 2012 |
| Atomica Limited | Real estate | 2013 |
| Attoe Strategy Ltd | Professional & scientific | 2026 |
| Attolero Limited | Wholesale & retail | 2025 |
| Auditly Limited | Information & communication | 2025 |
| Audyus Limited | Professional & scientific | 2004 |
| Aurum Investco Ltd | Real estate | 2022 |
| Ausper Capital Ltd | Administrative & support | 2024 |
| Auto Attentive Ltd | Wholesale & retail | 2007 |
| Auto Export Plus Ltd | Wholesale & retail | 2023 |
| Auto Service & Performance Ltd | Wholesale & retail | 2008 |
| Autobar Ltd | Hospitality | 2024 |