| AT the Agora Ltd | Wholesale & retail | 2026 |
| ATA Global Staffing Solutions Limited | Professional & scientific | 1995 |
| ATA Recruitment Limited | Professional & scientific | 2001 |
| Ataro Homes Ltd | Construction | 2024 |
| ATB Motor Engineers Limited | Wholesale & retail | 2014 |
| Atb.Uk Construction Limited | Construction | 2026 |
| Atb.Uk Solutions Limited | Real estate | 2026 |
| ATD Civils & Groundworks Ltd | Construction | 2018 |
| ATD Plant Limited | Construction | 2022 |
| ATD Vehicle Appearance Specialists Ltd | Administrative & support | 2024 |
| Atelier Vive Ltd | Wholesale & retail | 2023 |
| Athena Health Solutions Ltd | Health & social care | 2025 |
| Athena Occupational Health Limited | Health & social care | 2016 |
| Athens Grill Derby Ltd | Hospitality | 2022 |
| Atheon Services Limited | Administrative & support | 2018 |
| Athomes Group UK Ltd | Health & social care | 2024 |
| Atinian Ltd | Information & communication | 2018 |
| Atiya Healthcare Services Limited | Health & social care | 2010 |
| Atkin Comms Limited | Wholesale & retail | 2015 |
| Atkinson Wines Ltd | Manufacturing | 2017 |
| Atkiss Property Ltd | Real estate | 2024 |
| Atkk Properties Limited | Real estate | 2024 |
| Atlanthis Ltd | Hospitality | 2024 |
| Atlantic Projects Company (UK) Limited | Construction | 2004 |
| Atlantis Digital Ltd | Information & communication | 2021 |
| Atlas Accountancy Services Limited | Professional & scientific | 2023 |
| Atlas Enforcement Limited | Public administration | 2006 |
| Atlas Financial Services Limited | Professional & scientific | 2023 |
| Atlas Garage Ltd | Wholesale & retail | 2025 |
| Atlow Contracting Limited | Construction | 2007 |
| ATM Estates Ltd | Real estate | 2019 |
| ATM Tax Solutions Limited | Professional & scientific | 2025 |
| Atom Cakes & More Ltd | Manufacturing | 2025 |
| Atos Jiu-Jitsu Swadlincote Ltd | Education | 2024 |
| Atos Jiu-Jitsu Swadlincote Shop Ltd | Wholesale & retail | 2024 |
| Atsl Capital Ltd | Real estate | 2019 |
| Atsl Ltd | Real estate | 2016 |
| ATT Systems Limited | Manufacturing | 2020 |
| Attain Holdings Limited | Financial services | 2026 |
| Attain Investments Limited | Financial services | 2026 |
| Attain Properties Limited | Real estate | 2020 |
| Atten Bidco Limited | Financial services | 2021 |
| Atten Finance Limited | Financial services | 2021 |
| Atten Group Limited | Financial services | 2021 |
| Atten Midco Limited | Financial services | 2021 |
| Attenborough Law Limited | Professional & scientific | 2012 |
| Attended Ltd | Education | 2025 |
| Attention to Details Ltd | Administrative & support | 2026 |
| Attest UK Authentication Services Limited | Professional & scientific | 2014 |
| Attewell Properties Limited | Real estate | 2025 |
| Attic Media (Midlands) Ltd | Information & communication | 2018 |
| Attribes UK Ltd | Information & communication | 2018 |
| Atute Limited | Transport & logistics | 2025 |
| ATW Regulatory Services Limited | Professional & scientific | 2012 |
| Atwal Consulting Ltd | Professional & scientific | 2001 |
| Atwal Kingsway Limited | Construction | 1989 |
| Atwalz Limited | Transport & logistics | 2025 |
| AU Consulting Services Limited | Information & communication | 2017 |
| Auction 4 Cars Limited | Extraterritorial | 2015 |
| Auction News Limited | Information & communication | 2001 |
| Audby House Limited | Construction | 2021 |
| Audi Retrofits & Diagnostics Ltd | Wholesale & retail | 2025 |
| Audion Elektro Ltd. | Wholesale & retail | 1999 |
| Audiotometry Limited | Wholesale & retail | 2026 |
| Auditmeister Limited | Professional & scientific | 2016 |
| Auditree Limited | Agriculture & fishing | 2024 |
| AUDSLEY161 Limited | Administrative & support | 2017 |
| Aufregend Bar Group Limited | Hospitality | 2025 |
| Augmented IT Solutions Ltd | Information & communication | 2024 |
| Aujla DE23 #1 Ltd | Real estate | 2020 |
| Aujla DE24 Ltd | Real estate | 2019 |
| Aujla Exchange Ltd | Professional & scientific | 2022 |
| Aujla Group Ltd | Financial services | 2020 |
| Aujla Residential Holdings Ltd | Real estate | 2026 |
| Aulakh Haulage Ltd | Transport & logistics | 2021 |
| Aumento Derby Ltd | Hospitality | 2023 |
| AUN Traders Ltd | Wholesale & retail | 2025 |
| Aura (UK) Holdings Limited | Financial services | 2018 |
| Aura (UK) Ltd | Construction | 2014 |
| Aura Brands Ltd | Wholesale & retail | 2013 |
| Aura Collective Trading Ltd | Wholesale & retail | 2025 |
| Aura View Land Ltd | Construction | 2026 |
| Aurel Collections Limited | Wholesale & retail | 2026 |
| Aurora Asset Management (Derby) Ltd | Real estate | 2020 |
| Aurora Capital Management Ltd | Real estate | 2022 |
| Aurora Equine Well-Being and Movement CIC | Health & social care | 2026 |
| Aurora Express Logistics Ltd | Transport & logistics | 2025 |
| Aurora Fabrications Ltd | Manufacturing | 2024 |
| Aurora Music Corporation Ltd | Financial services | 2025 |
| Austen Fields Management Company Limited | Households | 2016 |
| Austin & Bryant Plumbing Ltd | Construction | 2025 |
| Austin Property Management Services Limited | Real estate | 2004 |
| Austin View (Longbridge Town Centre) Management Company Limited | Households | 2021 |
| Austin's Kitchen & Bathroom Installations Limited | Construction | 2018 |
| Authorised Territory Limited | Information & communication | 2018 |
| Auto - TEK Mobile Mechanics Ltd | Wholesale & retail | 2026 |
| Auto 1 Car Care Products Limited | Wholesale & retail | 2012 |
| Auto Aesthetics (Derby) Limited | Wholesale & retail | 2026 |
| Auto Body and Paints Limited | Wholesale & retail | 2009 |
| Auto Diagnostics Ltd | Wholesale & retail | 2024 |