| Atlantis Yachting Ltd | London | 2022 |
| Atlas Azure Ltd | London | 2025 |
| Atlas Coaching Ltd | Tonbridge | 2025 |
| Atlas Fitness Ltd | Eastleigh | 2019 |
| Atlas Football Group Ltd | Bridge Of Allan | 2026 |
| Atlas Group Holdings Ltd | London | 2025 |
| Atlas Gym Belfast Ltd | Belfast | 2024 |
| Atlas Gym Limited | Hickman Avenue Wolverhampton | 2003 |
| Atlas Gymnasium Club Limited | Bletchley | 2008 |
| Atlas Gyms 24/7 Limited | Bumpers Farm | 2015 |
| Atlas Leisure Limited | Southampton | 2006 |
| Atlas Lions MMA Limited | London | 2025 |
| Atlas North East Business Support Ltd | Gateshead | 2021 |
| Atlas North East CIC | Gateshead | 2012 |
| Atlas Overland Limited | Hexham | 2010 |
| Atlas Padel (Waltham Cross) Limited | Chigwell | 2026 |
| Atlas Rise Limited | Woodford Green | 2023 |
| Atlas Road Markings Limited | Hertfordshire | 2007 |
| Atlas Sounds Limited | London | 2016 |
| Atlas Sport Agencia Ltd | London | 2025 |
| Atlas Sports Capital Ltd | London | 2026 |
| Atlas Sports Ltd | London | 2025 |
| Atlas Sports Software Limited | Worcester | 2023 |
| Atlas Studios Ltd | Cheadle | 2015 |
| Atlas Tattoo Ltd | Musselburgh | 2025 |
| Atlas Theatre Company CIC | Sunderland | 2024 |
| Atlas Wanderers Travel Ltd | Rugby | 2025 |
| Atlas Youth Sports Club CIC | Birmingham | 2026 |
| ATLAS2024 Ltd | London | 2024 |
| Atlas: Rigging & Action Design Ltd | Farnborough | 2021 |
| Atlascore Racing Ltd | Stevenage | 2025 |
| Atlaseco Ltd | Tonbridge | 2021 |
| Atleta Consultancy Limited | Glasgow | 2013 |
| Atletico London Limited | London | 2025 |
| Atletico Warton CIC | Preston | 2025 |
| Atlib Ltd | London | 2018 |
| Atlib UK Ltd | London | 2020 |
| Atlp Recordings Limited | London | 2018 |
| ATM - About the Moment Ltd | London | 2026 |
| Atma Dance | London | 2010 |
| Atma Health & Fitness Ltd | Walsall | 2026 |
| Atma Limited | Ilford | 2024 |
| Atman - the International Federation of Yoga and Meditation | Chatteris | 2004 |
| Atmos Recordings Limited | Sheffield | 2024 |
| Atmos Visuals Limited | Petworth | 2019 |
| Atmosfear International Ltd | Southport | 2008 |
| Atmosora Events Ltd | Watford | 2026 |
| Atob Football Ltd | Chesterfield | 2024 |
| Atom FX Ltd | Warrington | 2023 |
| Atom Herders Limited | Pontefract | 2015 |
| Atom Music Ltd | London | 2019 |
| Atom Pictures Limited | London | 2003 |
| Atom Promotions Ltd | Worthing | 2015 |
| Atomic Entertainment Limited | Hove | 2019 |
| Atomic Force Productions Ltd | Brighton | 2011 |
| Atomic Galaxies Limited | Preston | 2026 |
| Atomic Partnership Ltd | Potters Bar | 1998 |
| Atomic Pyrotechnics Ltd | Swadlincote | 2024 |
| Atomic Racing Limited | Driffield | 2019 |
| Atomic Studios & Partners Limited | Milton Keynes | 2021 |
| Atomic Talent Agency Ltd | Warrington | 2025 |
| Atomic Tangerine Ltd | Southampton | 2015 |
| Atomic Theatre Arts Limited | Macclesfield | 2025 |
| Atomic Theatre Community Interest Company | Oxford | 2019 |
| Atomiser Ltd | London | 2025 |
| Atomizer Management Limited | Abingdon | 2012 |
| Atomizer Records Limited | Abingdon | 2017 |
| Atos JIU Jitsu UK Ltd | Sutton Coldfield | 2019 |
| Atoz Operations Limited | London | 2016 |
| ATP Gym Ltd | Bradford | 2019 |
| ATP Health & Fitness Ltd | Chippenham | 2009 |
| ATP Health and Fitness Norwich Limited | Norwich | 2011 |
| ATP Lifestyle Ltd | Wedmore | 2025 |
| ATP Ventures Ltd. | Edinburgh | 2004 |
| Atpl Shows Ltd | London | 2020 |
| ATR Theatre Company Ltd | London | 2023 |
| Atrek Ltd | Wolverhampton | 2025 |
| Atrium Fitness Ltd | Woodford Green | 2008 |
| Atrium Talent Limited | Liverpool | 2006 |
| Atromin Limited | Basildon | 1985 |
| ATS Arts Ltd | London | 2018 |
| ATS Elite Events Ltd | London | 2024 |
| ATS Football Ltd | Enfield | 2023 |
| ATS Motorsport Limited | Barnsley | 2024 |
| ATS Racing Limited | Walsall | 2022 |
| Atsli Casting Limited | Cardiff | 2003 |
| Atsoccercamps Limited | Stourport-On-Severn | 2015 |
| Attachment London Ltd | London | 2015 |
| Attack Force Music Limited | Manchester | 2018 |
| Attack Golf Limited | Witney | 2013 |
| Attaie Limited | London | 2025 |
| Attain & Sustain Health & Fitness Limited | Cardiff | 2017 |
| Attention IS the New OIL Limited | London | 2026 |
| Attentive Entertainment Group Ltd | London | 2022 |
| Attercliffe Gymnastics Academy Limited | Sheffield | 2017 |
| Attfield Theatre Company Limited | Oswestry | 2000 |
| Attheland Ltd | Coventry | 2026 |
| Attic Blue Limited | Buckhurst Hill | 2014 |
| Attic Events Ltd | Irvine | 2017 |
| Attic Studio Limited | Bootle | 2010 |