| AMW Automation Ltd | Information & communication | 2026 |
| AMY on Bera Ltd | Information & communication | 2026 |
| AMY Tetchner Ltd | Arts & recreation | 2019 |
| Amy's Animals Ltd | Wholesale & retail | 2023 |
| Ananya Homes Ltd | Real estate | 2025 |
| Anathi Limited | Real estate | 2025 |
| Anchor Recruitment Limited | Administrative & support | 2017 |
| Ancora Children’S Homes Limited | Health & social care | 2022 |
| Anderson Brothers Plumbing Heating & Property Maintenance Limited | Construction | 2010 |
| Anderson Heating and Plumbing Ltd | Construction | 2025 |
| Andrew Devine Consultancy Services Ltd | Information & communication | 2019 |
| Andy King Limited | Construction | 2013 |
| Anerley Road Properties Ltd | Households | 2017 |
| Angel Carpet UK Limited | Wholesale & retail | 2018 |
| Angel Development Company Limited | Construction | 2014 |
| Angel Group Holdings Limited | Wholesale & retail | 2025 |
| Angie Hooper Consulting Limited | Professional & scientific | 2023 |
| Angiu Limited | Financial services | 2017 |
| Angle Place Limited | Households | 2004 |
| Anglia Battery and Filter Co Limited | Wholesale & retail | 2003 |
| Anglian Civils Formwork Ltd | Construction | 2021 |
| Anglo Boxon Limited | Administrative & support | 2022 |
| Anidea Business Ltd | Administrative & support | 2017 |
| Anita James Counselling Ltd | Health & social care | 2020 |
| Anitech Solution Service Limited | Professional & scientific | 2019 |
| Another Day Events Ltd | Professional & scientific | 2018 |
| Antarctica Search Ltd | Administrative & support | 2021 |
| Anthony Hurlstone Design Ltd | Professional & scientific | 2015 |
| Anthony James Transport Ltd | Transport & logistics | 2025 |
| Anthro Architecture Ltd | Professional & scientific | 2022 |
| Antique Unique Upholstery Limited | Other services | 2020 |
| Anvil Manufacturing Consulting Limited | Professional & scientific | 2026 |
| ANY Car Buyer 24/7 Ltd | Wholesale & retail | 2022 |
| Anyhood Limited | Arts & recreation | 2017 |
| Aona Digital Limited | Professional & scientific | 2025 |
| Aori Consulting Ltd | Professional & scientific | 2021 |
| Apate Advisory Limited | Information & communication | 2025 |
| Apcai Ltd | Construction | 2009 |
| Apcgi Ltd | Information & communication | 2021 |
| Apeiron Investments Limited | Real estate | 2022 |
| Aperture - Natural Light Consulting Limited | Professional & scientific | 2026 |
| Apex Contractors (KA) Ltd | Wholesale & retail | 2024 |
| APL Agency Limited | Administrative & support | 2022 |
| APL Plumbing and Heating Engineers Limited | Construction | 2018 |
| APM Projects Limited | Professional & scientific | 2007 |
| APM Property Investments Ltd | Real estate | 2021 |
| Apollo House PMC Limited | Real estate | 2017 |
| Apoyo Ltd | Real estate | 2021 |
| Apple Core Diamond Drilling Limited | Construction | 2017 |
| Applespa Limited | Other services | 2022 |
| Appliance Force Limited | Extraterritorial | 2000 |
| Apposphere Limited | Administrative & support | 2014 |
| Apppay Collective Limited | Administrative & support | 2017 |
| Apricity Club Ltd | Wholesale & retail | 2024 |
| Apron Design Limited | Construction | 2015 |
| Aptech Consultants Limited | Information & communication | 2007 |
| AQC Group Holdings Ltd | Financial services | 2025 |
| Aqua Nails Limited | Health & social care | 2004 |
| Aqua Pharmacy Ltd | Wholesale & retail | 2012 |
| Aqua Prescriptions Limited | Wholesale & retail | 2022 |
| Aquajet Power Ltd | Construction | 2019 |
| Aquarrii Capital Limited | Professional & scientific | 2020 |
| Aquatech Plumbing and Heating Limited | Construction | 2016 |
| Aquilacom Limited | Information & communication | 2008 |
| AR Spark Electrical Ltd | Construction | 2024 |
| Arabian Olive OIL Ltd | Wholesale & retail | 2019 |
| Aramalia Ltd | Other services | 2021 |
| ARB Construction Ltd | Construction | 2021 |
| ARC Capital Partners Limited | Administrative & support | 2023 |
| ARC Construction Group Limited | Construction | 2013 |
| ARC Insulation Services Ltd | Construction | 2025 |
| ARC Landscapes Limited | Administrative & support | 2019 |
| Arca Assets (Essex) Limited | Administrative & support | 2020 |
| Arca Packaging Limited | Other services | 2010 |
| Arcachon Limited | Other services | 1998 |
| Arcadian Corporation Limited | Financial services | 2003 |
| Archea Design Ltd | Professional & scientific | 2019 |
| Architectural Fire Systems Limited | Wholesale & retail | 2013 |
| Architectural Stainless Swimming Pool Products Ltd | Manufacturing | 2003 |
| Archway Apartments Limited | Real estate | 2014 |
| Arcstilius Ltd | Construction | 2012 |
| Arctic Tiger Holdings Limited | Administrative & support | 2022 |
| Arden Roofing Company Limited | Real estate | 1977 |
| Ardmat Services Limited | Other services | 2013 |
| Ardmore Construction Group Ltd | Construction | 2019 |
| Ardmore Construction Limited | Construction | 1974 |
| Ardmore Fitout Ltd | Construction | 2019 |
| Ardmore Hotels & Commercial Ltd | Construction | 2019 |
| Ardmore Major Projects Ltd | Construction | 2019 |
| Ardmore Regeneration Ltd | Construction | 2019 |
| Ardore London Ltd | Wholesale & retail | 2024 |
| Area 15 CN Limited | Other services | 2024 |
| Ares Tactical Concepts Limited | Arts & recreation | 2019 |
| Arestor Limited | Manufacturing | 2016 |
| ARF Designs Ltd | Professional & scientific | 2015 |
| ARF Investments Ltd | Real estate | 2018 |
| Arich Trading Ltd | Wholesale & retail | 2024 |
| Aristol Limited | Construction | 2009 |
| Arma Fire Consultants Limited | Public administration | 2017 |
| Armchair Enterprises Limited | Information & communication | 2011 |