| Asllimoss Ltd | Transport & logistics | 2018 |
| ASM (Yorkshire) Limited | Transport & logistics | 2020 |
| ASM Partners Ltd | Real estate | 2018 |
| ASM Truck Parks Limited | Transport & logistics | 2024 |
| ASM Ventures Limited | Financial services | 2025 |
| Asmk Property UK Limited | Real estate | 2023 |
| Aspiedent CIC | Professional & scientific | 2014 |
| Aspirations People Ltd | Financial services | 2016 |
| Aspirations RCH Residential Children's Homes Ltd | Health & social care | 2025 |
| Aspire Accommodation Limited | Real estate | 2016 |
| Aspire Bradford Ltd | Other services | 2026 |
| Aspire Childrens Home Ltd | Health & social care | 2024 |
| Aspire Civil Engineering Supplies Ltd | Construction | 2022 |
| Aspire Electrical Services Ltd | Construction | 2016 |
| Aspire Electrical West Yorkshire Limited | Construction | 2025 |
| Aspire Furnishings Ltd | Wholesale & retail | 2018 |
| Aspire Global Ventures Ltd | Real estate | 2022 |
| Aspire Hair Studio Ltd | Other services | 2018 |
| Aspire Midlands Holdings Ltd | Construction | 2021 |
| Aspire Munderfield Ltd | Construction | 2021 |
| Aspire Pathways Support Ltd | Health & social care | 2025 |
| Aspire Pro Coaching Limited | Education | 2025 |
| Aspire Social UK Ltd | Professional & scientific | 2023 |
| Aspire UK Care Services Ltd | Health & social care | 2023 |
| Aspire Unity Ltd | Information & communication | 2024 |
| Aspire Utility Training Limited | Education | 2025 |
| Aspiring Landscapes London Limited | Administrative & support | 2018 |
| Aspiring Scholars Ltd | Education | 2023 |
| ASQ Consultants Ltd | Information & communication | 2014 |
| ASQ Snooker Centre Ltd | Education | 2026 |
| ASR Electrical & Renewables Ltd | Construction | 2021 |
| ASR Performance (ASR) Ltd | Wholesale & retail | 2026 |
| Assembly Bradford Ltd. | Real estate | 2016 |
| Asset Rock AXE ST Ltd | Real estate | 2025 |
| Assist Home Care Ltd | Health & social care | 2009 |
| Assist Ltd | Wholesale & retail | 2025 |
| Assist Properties Ltd | Real estate | 2019 |
| Assisted Lives Gloucester Ltd | Health & social care | 2024 |
| Assisted Lives Holdings Ltd | Financial services | 2018 |
| Assisted Lives Investments Ltd | Real estate | 2025 |
| Assisted Lives Ltd | Health & social care | 2011 |
| Assisted Lives Worcester Ltd | Health & social care | 2024 |
| Asspire Recruitment Ltd | Administrative & support | 2025 |
| Assured Autos Ltd | Wholesale & retail | 2019 |
| Assured GAS Care Ltd | Construction | 2023 |
| Assuring Quality Ltd | Information & communication | 2015 |
| Aston GCS Limited | Construction | 2018 |
| Astonish Holdings Limited | Manufacturing | 1997 |
| Astonish Products Limited | Extraterritorial | 1997 |
| Astram Goods Ltd | Professional & scientific | 2018 |
| Astro Autocare Ltd | Manufacturing | 2025 |
| Astthim Ltd | Wholesale & retail | 2024 |
| Asura Holding Ltd | Health & social care | 2016 |
| Asworld Ltd | Wholesale & retail | 2022 |
| ASY Products Limited | Manufacturing | 2023 |
| ASZA257 Ltd | Information & communication | 2026 |
| AT Beauty and Nails Ltd | Other services | 2025 |
| AT Consulting Group Ltd | Professional & scientific | 2025 |
| AT Trade Ltd | Wholesale & retail | 2023 |
| Atah's Home Group Limited | Real estate | 2025 |
| Atahs Cash & Carry Limited | Wholesale & retail | 2023 |
| Atal Designs Ltd | Professional & scientific | 2024 |
| ATB Hants Limited | Administrative & support | 2025 |
| ATC Mart Ltd | Wholesale & retail | 2024 |
| ATE Solutions (Yorkshire) Limited | Information & communication | 2013 |
| Ateb Bars Limited | Hospitality | 2019 |
| Ategbe Brewery Ltd | Hospitality | 2022 |
| Ategbe Taverns Ltd | Hospitality | 2022 |
| Atelier Vitae Ltd | Other services | 2026 |
| Atemplonuevo Ltd | Health & social care | 2017 |
| Atestd Limited | Information & communication | 2021 |
| ATG Network Ltd | Transport & logistics | 2024 |
| Athena Sport Ltd | Arts & recreation | 2022 |
| Athenium House Limited | Construction | 2024 |
| Athi Traders Ltd | Wholesale & retail | 2025 |
| Ativa Investments Ltd | Real estate | 2019 |
| Atkins LGV Training Limited | Education | 2005 |
| Atkinson IP Consulting Limited | Professional & scientific | 2013 |
| ATL 1 Ltd | Other services | 2024 |
| Atlanta Pallets Limited | Manufacturing | 2017 |
| Atlantis IT Ltd | Information & communication | 2019 |
| Atlas Fabrication & Welding Ltd | Manufacturing | 2024 |
| Atlas Nights Limited | Real estate | 2024 |
| Atlas Splicing Ltd | Construction | 2022 |
| Atlas UK Investments Ltd | Real estate | 2025 |
| Atlastrade Ltd | Wholesale & retail | 2025 |
| ATM Corporate Events Limited | Other services | 2001 |
| Atmer Tuitions and Skills Hub Ltd | Education | 2026 |
| Atoz Fireworks Ltd | Wholesale & retail | 2025 |
| Atoz Holidays Limited | Administrative & support | 2025 |
| Atoz Ltd | Transport & logistics | 2025 |
| Atozadvert Ltd | Information & communication | 2024 |
| ATP Gym Ltd | Arts & recreation | 2019 |
| Atpharmaceuticals Ltd | Health & social care | 2025 |
| ATR Catering Supplies Limited | Wholesale & retail | 1998 |
| ATR Developments Limited | Real estate | 2025 |
| Atrium Wealth Management Limited | Financial services | 2017 |
| Atrium Zeal Ltd | Wholesale & retail | 2025 |
| Attendin Ltd | Administrative & support | 2025 |
| Attitude Cycles Ltd | Manufacturing | 2016 |