| Asset Stourbridge LLP | | 2017 |
| Assetlink Limited | Construction | 2011 |
| Assetsinfra Limited | Real estate | 2012 |
| Assis AV & Electrical Solutions Ltd | Construction | 2018 |
| Assoc. 16 Clarence Road Residents Company Limited | Real estate | 2002 |
| Assorted Collections Limited | Wholesale & retail | 2018 |
| Assurient Ltd | Information & communication | 2025 |
| AST Estates Limited | Real estate | 2024 |
| AST Traders Ltd | Wholesale & retail | 2025 |
| Astamade Ltd | Wholesale & retail | 2022 |
| Astarbuildingservices Ltd | Construction | 2025 |
| Aster Homecare UK Ltd | Administrative & support | 2024 |
| Astera Deli Ltd | Wholesale & retail | 2017 |
| Asterisk Consulting Limited | Information & communication | 2022 |
| Aston Bond Law Limited | Professional & scientific | 2012 |
| Aston Services Group Ltd | Administrative & support | 1967 |
| Astoria Associates Ltd | Wholesale & retail | 2003 |
| Astoria Heights Residents Management Company Limited | Households | 2015 |
| Astos Accounting Ltd | Professional & scientific | 2026 |
| Astounding Systems Ltd | Wholesale & retail | 2010 |
| Astra Vita Ltd | Real estate | 2025 |
| Astrad Tools Limited | Administrative & support | 2004 |
| Astrix Paradigm Ltd | Wholesale & retail | 2024 |
| Astron Engineers Limited | Construction | 2012 |
| Astron Services Limited | Construction | 2024 |
| ASZ Services Limited | Administrative & support | 2026 |
| AT Newco 20 Limited | Extraterritorial | 2014 |
| AT51 Limited | Wholesale & retail | 2020 |
| ATC Flooring Ltd | Wholesale & retail | 2023 |
| ATC Rail Consulting Ltd | Construction | 2016 |
| ATC Scaffolders Ltd | Construction | 2026 |
| ATC Trendtok Ltd | Wholesale & retail | 2025 |
| Atchima Invest Limited | Wholesale & retail | 2018 |
| Atcore Technology Group Limited | Professional & scientific | 2014 |
| Atecs High Wycombe Limited | Transport & logistics | 2018 |
| Ateeq Yaqoob Ltd | Wholesale & retail | 2025 |
| Atelier Walker Ltd | Real estate | 2023 |
| Atelio Ltd | Wholesale & retail | 2025 |
| Athel Investments Ltd | Real estate | 2019 |
| Athema Services Limited | Wholesale & retail | 2007 |
| Athena Market Access Solutions Ltd. | Professional & scientific | 2016 |
| Athletic Performance Ltd | Arts & recreation | 2024 |
| Athora Water Ltd | Wholesale & retail | 2026 |
| Athus Ltd | Wholesale & retail | 2018 |
| Atif Ltd | Wholesale & retail | 2023 |
| Atlanta Stone World Ltd | Manufacturing | 2025 |
| Atlantic Bizz Ltd | Wholesale & retail | 2015 |
| Atlantic Choice Limited | Transport & logistics | 2014 |
| Atlantic IT Services Limited | Information & communication | 2023 |
| Atlantic Payroll Ltd | Professional & scientific | 2022 |
| Atlantis Asset Investments Ltd | Hospitality | 2022 |
| Atlantis GB Holdings Ltd | Wholesale & retail | 2025 |
| Atlantis GBL Ltd | Wholesale & retail | 2019 |
| Atlantis Global Ltd | Wholesale & retail | 2010 |
| Atlantis Invest Ltd | Wholesale & retail | 2018 |
| Atlantis Lounge and Restaurant Ltd | Other services | 2020 |
| Atlantis Rentals and Leasing Ltd | Administrative & support | 2019 |
| Atlantis Roofing & Upvc Specialists Ltd | Construction | 2024 |
| Atlas 82 HRW Limited | Real estate | 2023 |
| Atlas Aston Limited | Financial services | 2023 |
| Atlas Cleaning Limited | Administrative & support | 2023 |
| Atlas Commercial Property Limited | Construction | 2014 |
| Atlas Contractors Limited | Administrative & support | 2024 |
| Atlas CPI Benfleet Limited | Financial services | 2023 |
| Atlas Digital Holdings Ltd | Information & communication | 2026 |
| Atlas FM Payroll Limited | Administrative & support | 2023 |
| Atlas FM Services Limited | Administrative & support | 2024 |
| Atlas Operations Payroll Limited | Administrative & support | 2025 |
| Atlas Packing Services Limited | Manufacturing | 1996 |
| Atlas Payroll Limited | Administrative & support | 2023 |
| Atlas Structural Consultants Ltd | Professional & scientific | 2019 |
| Atluri Enterprises Ltd | Real estate | 2024 |
| Atomic IT Limited | Information & communication | 1989 |
| Atoz Mobile Junction Ltd | Wholesale & retail | 2015 |
| ATQ 62 Ltd | Transport & logistics | 2023 |
| Atsun Ltd | Other services | 2017 |
| ATTARI786 Ltd | Wholesale & retail | 2025 |
| Attire's TAG Limited | Wholesale & retail | 2021 |
| Attraversiamo Ltd | Professional & scientific | 2011 |
| ATV Transport Ltd | Transport & logistics | 2023 |
| Atyab Tamim Limited | Manufacturing | 2024 |
| AU Practitioner Ltd | Health & social care | 2023 |
| Audaciousink Limited | Arts & recreation | 2025 |
| Audi Volkswagen Independent Technicians (Avit) Limited | Wholesale & retail | 2007 |
| Audi Volkswagen Independent Technicians UK Limited | Wholesale & retail | 2019 |
| Audio Visual Install Techs Ltd | Construction | 2022 |
| Audio Visual Live Limited | Administrative & support | 2009 |
| Aujla Distribution Ltd | Transport & logistics | 2020 |
| Aujla Haulage Ltd | Transport & logistics | 2016 |
| Aujla Roofing Ltd | Construction | 2026 |
| Aukconstruction Ltd | Construction | 2026 |
| Aulakh Builds Ltd | Construction | 2024 |
| Aulakh Group Ltd | Real estate | 2020 |
| Auny Ltd | Hospitality | 2022 |
| Aura Beauty Services Ltd | Other services | 2026 |
| Aura Care Homes Limited | Health & social care | 2017 |
| Aura Elite Limited | Education | 2025 |
| Aura Host Limited | Hospitality | 2025 |
| Aura Quality Stone Ltd | Manufacturing | 2022 |
| Auraarc Ltd | Information & communication | 2026 |