| Ahora Project Services Limited | Professional & scientific | 2011 |
| AHS Motorsport Limited | Wholesale & retail | 2014 |
| AIM Financial Planning Limited | Real estate | 2003 |
| Airfield Trailer Store Limited | Transport & logistics | 2017 |
| Airmasters (UK) Ltd | Other services | 2014 |
| AJ West Consulting Limited | Professional & scientific | 2024 |
| AJ Wilks Environmental Health Consultancy Limited | Professional & scientific | 2019 |
| AJB Carpentry & Maintenance Limited | Construction | 2018 |
| AJE Amusements Limited | Other services | 2020 |
| AJE Greencrest Storage Ltd | Transport & logistics | 2025 |
| Akbar Property Group Ltd | Real estate | 2024 |
| AKU & STR Medical Ltd | Health & social care | 2025 |
| Alan James (Coventry) Limited | Extraterritorial | 1984 |
| Alanah Trading Lutterworth Ltd | Wholesale & retail | 2025 |
| Albusco Digital Ltd | Information & communication | 2026 |
| ALC Development Ltd | Construction | 2017 |
| Alces Medical Ltd | Health & social care | 2026 |
| Alchemy IT Ltd | Information & communication | 2025 |
| Alcuin Ltd | Administrative & support | 2025 |
| Alegria Coterie Limited | Professional & scientific | 2011 |
| Alfie & Archie Properties Ltd | Real estate | 2021 |
| Alfie Francis Limited | Wholesale & retail | 2022 |
| Alkerton 2022 Limited | Administrative & support | 2022 |
| Alkerton 2025 Limited | Real estate | 2026 |
| ALL Made UP Blinds Ltd | Manufacturing | 2016 |
| Allari Partners Limited | Professional & scientific | 2025 |
| Allens Hair & Beauty Supplies Ltd | Other services | 2013 |
| Aller Oslo Ltd | Real estate | 2024 |
| Alney (U.K.) Limited | | 1976 |
| Alphamix Concrete and Screed Ltd | Manufacturing | 2019 |
| Althea Women's Health Ltd | Health & social care | 2024 |
| Alto Hearing Ltd | Wholesale & retail | 2022 |
| Altrina Ltd | Information & communication | 2022 |
| Altus Controls Limited | Manufacturing | 2020 |
| Amalgamated Marketing Services (Freight Forwarders) Limited | Transport & logistics | 2000 |
| Amanda Black Menopause Coaching Limited | Health & social care | 2020 |
| Amarval Partners Ltd | Administrative & support | 2021 |
| Amber Aviation Ltd | Information & communication | 2005 |
| Amber Food and Catering Ltd | Hospitality | 2019 |
| Amend Business Consulting Ltd | Administrative & support | 2026 |
| Amethyst HR Limited | Administrative & support | 2015 |
| Amiratna Limited | Other services | 2023 |
| Amlcc Digital Limited | Administrative & support | 2012 |
| AMM Housing Ltd | Real estate | 2019 |
| Ammar Naser Ltd | Real estate | 2015 |
| Amsa Private Limited | Health & social care | 2016 |
| Amsa Property Limited | Real estate | 2021 |
| Amusement Engineering Ltd. | Manufacturing | 2011 |
| Analyticai Data Solutions Ltd | Professional & scientific | 2025 |
| Andimone Ltd | Administrative & support | 2023 |
| Andy Poole Machinery Limited | Manufacturing | 2009 |
| Angel Holistic Care Limited | Health & social care | 2018 |
| Anglia Insulation Systems Limited | | 1987 |
| Anglo Engineering Services Limited | Extraterritorial | 1983 |
| ANH Medical Ltd | Health & social care | 2024 |
| Animatefx Ltd | Information & communication | 2013 |
| ANN Lewis Ltd | Health & social care | 2002 |
| Anniseeds Ltd | Manufacturing | 2023 |
| Anovi Holdings Limited | Financial services | 2019 |
| Anti-Money Laundering Compliance Company Limited | Professional & scientific | 2002 |
| Anyglass (Rugby) Ltd | Manufacturing | 2023 |
| Anyglass Holdings Ltd | Real estate | 2025 |
| AP Event & Production Ltd | Arts & recreation | 2014 |
| AP Handyman Home & Garden Services Ltd | Construction | 2022 |
| APD Recruitment Limited | Administrative & support | 2021 |
| APE Grab Hire Rugby Limited | Water & waste | 2015 |
| Apex Graphics Ltd | Professional & scientific | 2012 |
| Apex Plant Hire Limited | Extraterritorial | 2015 |
| Apex Plant Ltd | Administrative & support | 2012 |
| APL Sign and Print Ltd | Administrative & support | 2026 |
| Apollo Labs Ltd | Other services | 2025 |
| Applecross Rentals Ltd | Real estate | 2017 |
| Appledeck Limited | Real estate | 2003 |
| Appletrees Health Ltd | Health & social care | 2025 |
| Appman Ltd | Information & communication | 2025 |
| Apprenticeship Recruitment Service Ltd | Education | 2015 |
| Aquasave Ltd | Manufacturing | 2018 |
| Arboret Limited | Information & communication | 1981 |
| Archetypal Potential Ltd | Professional & scientific | 2015 |
| Archway Gallery Limited | Wholesale & retail | 2018 |
| Arcomoto Ltd | Professional & scientific | 2019 |
| Areca Solutions Limited | Information & communication | 2024 |
| Arieffabuhassan Ltd | Health & social care | 2024 |
| Arkm Limited | Financial services | 2017 |
| Arkqa Limited | Information & communication | 2015 |
| Armourgeddon Holdings Limited | Financial services | 2018 |
| Armourgeddon Limited | Arts & recreation | 2006 |
| Armstrong Express Ltd | Transport & logistics | 2005 |
| Armstrong Fitness Limited | Arts & recreation | 2020 |
| Armstrong Group of Companies Limited | Financial services | 2020 |
| Armstrong Logistics Limited | Transport & logistics | 2001 |
| Armstrong Property Management Limited | Real estate | 2020 |
| Armstrong Vehicle Services Limited | Wholesale & retail | 2020 |
| Armw Ventures Limited | Wholesale & retail | 2023 |
| Aroma Care People Ltd | Health & social care | 2015 |
| Arpan Shrivastava Ltd | Other services | 2014 |
| Arrant Limited | Professional & scientific | 2013 |
| Artgrove Designs Limited | Professional & scientific | 1991 |
| Arts of the Sky Ltd | Professional & scientific | 2024 |
| ASH Care Services Salisbury Ltd | Health & social care | 2013 |