| Asker Group Limited | Construction | 2025 |
| Asker Property Limited | Real estate | 2026 |
| Asla Holdings Limited | Real estate | 2022 |
| Aslam Lancashire Mailing Ltd | Transport & logistics | 2023 |
| Asland Properties Limited | Real estate | 2023 |
| Asma Rehman Ltd | Other services | 2007 |
| ASN Preston Limited | Health & social care | 2025 |
| ASO Properties Ltd | Real estate | 2022 |
| ASP Logistics Ltd | Transport & logistics | 2013 |
| ASP Sports and Medical Services Limited | Other services | 2011 |
| Aspen Garden Maintenance (Garstang) Ltd | Administrative & support | 2024 |
| Asphyxia Films Ltd | Information & communication | 2026 |
| Aspiration Consultancy Limited | Professional & scientific | 2021 |
| Aspire Clinical Limited | Health & social care | 2025 |
| Aspire Creative Services Limited | Information & communication | 2015 |
| Aspire Immigration Ltd | Professional & scientific | 2020 |
| Aspire Orthopaedics Limited | Health & social care | 2018 |
| Aspire Workforce Management Ltd | Professional & scientific | 2025 |
| Aspiring Pathways Ltd | Education | 2024 |
| Aspr Property Limited | Real estate | 2023 |
| ASR Haulage Ltd | Transport & logistics | 2026 |
| Asrev Healthcare Ltd | Wholesale & retail | 2023 |
| Asrev Holdings Ltd | Real estate | 2025 |
| Asrev Pharma UK Ltd | Wholesale & retail | 2023 |
| Assessability Limited | Professional & scientific | 2002 |
| Asset and Business Finance Limited | Financial services | 2017 |
| Asset Recruitment Ltd | Administrative & support | 2020 |
| ASSET22 Ltd | Real estate | 2022 |
| Assetwize Properties Limited | Real estate | 2023 |
| Assi Ltd | Real estate | 2026 |
| Assistech Limited | Wholesale & retail | 2013 |
| Associate Therapists Ltd | Health & social care | 2011 |
| Assured Cleaning Services Limited | Administrative & support | 2002 |
| Assured Living Housing Association Limited | Hospitality | 2008 |
| Assured Solutions Communications (ASC) Ltd | Information & communication | 2026 |
| Assured Training Ltd | Education | 2025 |
| Astaban Contracts Limited | Construction | 1997 |
| Aster Global Co. Ltd | Wholesale & retail | 2022 |
| Aston Greenwood Limited | Manufacturing | 2015 |
| Astoria Care Ltd | Health & social care | 2021 |
| Astra Door Controls Ltd | Manufacturing | 2018 |
| Astrium Limited | Extraterritorial | 2019 |
| Astro Signs Limited | Administrative & support | 2023 |
| Astromar Limited | Wholesale & retail | 2025 |
| Asturian Gate Management Company Limited | Households | 2003 |
| Asturian House Management Company Limited | Real estate | 2018 |
| Astute Asset Management Limited | Real estate | 2016 |
| Astute Energy Ltd | Construction | 2025 |
| Astute Funding Limited | Financial services | 2014 |
| Astute HR Limited | Administrative & support | 2024 |
| ASTUTE3D Limited | Wholesale & retail | 2024 |
| Asurelife Ltd | Financial services | 2024 |
| ASV Healthcare Limited | Health & social care | 2018 |
| ASW Consulting Services Ltd | Professional & scientific | 2019 |
| AT Amenities Limited | Wholesale & retail | 2016 |
| AT Capital Investments Limited | Real estate | 2012 |
| AT Home Pet Care Limited | Professional & scientific | 2020 |
| AT Investments Limited | Real estate | 2005 |
| AT Luxe Rentals Ltd | Real estate | 2025 |
| AT Properties Limited | Real estate | 2003 |
| ATB Computer Services Ltd | Information & communication | 2011 |
| ATC Facilities Limited | Hospitality | 2017 |
| ATC Superheroes Limited | Education | 2017 |
| Atchchu Limited | Wholesale & retail | 2023 |
| Atchia Kitchens and Bedrooms Ltd | Construction | 2023 |
| Atelier Blanc Ltd | Health & social care | 2025 |
| ATF HW Ltd | Construction | 2026 |
| ATG Contracts Limited | Construction | 2002 |
| Atharhub Ltd | Wholesale & retail | 2025 |
| Athena Aerospace Ltd | Extraterritorial | 2025 |
| Athena Engineering Limited | Other services | 2008 |
| Atheriel Imaging Limited | Health & social care | 2022 |
| Atherora Ltd | Health & social care | 2022 |
| Atherton and Cookson Limited | Extraterritorial | 2021 |
| Atherton Productions Ltd | Information & communication | 2024 |
| Atherton Valet Centre Ltd | Administrative & support | 2022 |
| Athletic Mind Coaching & Training Ltd | Education | 2025 |
| Athol Street Holdings Limited | Financial services | 2025 |
| Atim Legal Consulting Ltd | Professional & scientific | 2022 |
| Atique Healthcare Ltd | Health & social care | 2026 |
| Atiyyah Limited | Real estate | 2007 |
| Atkinson Lettings and Maintenance Ltd | Real estate | 2026 |
| Atkinson Trailer Hire Limited | Administrative & support | 2014 |
| Atkinson World Digital Limited | Professional & scientific | 2011 |
| Atkinson’S Auto Tech Ltd | Construction | 2023 |
| Atlantic Industrials Limited | Wholesale & retail | 1998 |
| Atlantic Innovations International Limited | Manufacturing | 2019 |
| Atlas Codeworks Limited | Information & communication | 2026 |
| Atlas GT Limited | Professional & scientific | 2025 |
| Atlas Online Ltd | Information & communication | 2020 |
| Atlas Plumbing and Heating NW Limited | Construction | 2024 |
| Atlas Prime Estates Ltd | Real estate | 2026 |
| Atlas Project Solutions Ltd | Professional & scientific | 2025 |
| Atlas Residential Children's Homes Ltd | Real estate | 2021 |
| Atletico Warton CIC | Arts & recreation | 2025 |
| Atman Medical UK Ltd | Health & social care | 2010 |
| Atmosklear Limited | Professional & scientific | 2021 |
| Atom Communications Ltd | Information & communication | 2023 |
| Atom Electronics Ltd | Wholesale & retail | 2023 |
| Atomic Computer Systems Limited | Information & communication | 2002 |