| Atherton Collieries FC C.I.C. | Manchester | 2010 |
| Atherton Cricket Club Limited | Manchester | 2019 |
| Atherton Indoor Range Ltd | Atherton | 2023 |
| Atherton L.R.A.F.C. Limited | Manchester | 1989 |
| Atherton Laburnum Rovers Juniors CIC | Manchester | 2025 |
| Atherton Racing Ltd | Oswestry | 2011 |
| Athes Performance Ltd | Sale | 2016 |
| Athier Creative Ltd | London | 2010 |
| Athis Limited | Horsham | 2002 |
| Athl Haus Ltd | London | 2026 |
| Athleta Olympia Ltd | Wokingham | 2023 |
| Athlete 360 USA Ltd | Sutton-In-Ashfield | 2026 |
| Athlete Academy Ltd | Brockworth | 2006 |
| Athlete Connect Ltd | London | 2024 |
| Athlete Fit HQ Ltd | Stoke-On-Trent | 2019 |
| Athlete Focused Central, Tayside and Fife Ltd | Glasgow | 2025 |
| Athlete Focused Edinburgh Ltd | Kirkliston | 2023 |
| Athlete Focused Glasgow Limited | Glasgow | 2016 |
| Athlete Focused London City Ltd | London | 2026 |
| Athlete Focused NI Ltd | Ballymoney | 2021 |
| Athlete LAB UK Ltd | Ellesmere Port | 2024 |
| Athlete London Limited | Kingston Upon Thames | 2009 |
| Athlete Management International Limited | Sheffield | 2010 |
| Athlete Movement Holdings Ltd | Liphook | 2021 |
| Athlete Movement Limited | Liphook | 2017 |
| Athlete PER4MANCE Ltd | Sandbach | 2020 |
| Athlete Performance Preparation Ltd | Swansea | 2023 |
| Athlete Training Centre Limited | Clydebank | 2023 |
| Athlete Way Always (AWA) Ltd | Croydon | 2024 |
| ATHLETE1ST Campus Limited | Alderley Edge | 2021 |
| Athleteapex Ltd | Bootle | 2024 |
| Athletefocus Limited | Bideford | 2020 |
| Athletes HQ Limited | London | 2025 |
| Athletes in Schools Limited | Leeds | 2024 |
| Athletes Only Limited | Glasgow | 2022 |
| Athletic Boxing Club CIC | Doncaster | 2024 |
| Athletic Club 2 Ltd | Leeds | 2017 |
| Athletic Club Ltd | Leeds | 2016 |
| Athletic Club Marketing Ltd | Leeds | 2019 |
| Athletic Development and Recovery Ltd | Sale | 2021 |
| Athletic Development Club Ltd | London | 2015 |
| Athletic Evolution Consulting Ltd | Edinburgh | 2023 |
| Athletic FC Ltd | London | 2025 |
| Athletic Football Group Ltd | Oxford | 2024 |
| Athletic Intelligence Ltd | Ilford | 2006 |
| Athletic Newham FC Ltd | London | 2017 |
| Athletic Performance Academy (APA) Limited | Milton Keynes | 2011 |
| Athletic Performance Group Limited | Guildford | 2024 |
| Athletic Performance Ltd | Slough | 2024 |
| Athletica Fitness & Strength Ltd | Leigh-On-Sea | 2022 |
| Athletica Ltd | Glasgow | 2013 |
| Athleticdev Ltd | Dunmow | 2023 |
| Athletico Buckshaw Futsal Ltd | Chorley | 2018 |
| Athletico Seville Fitness Ltd | Reading | 2025 |
| Athleticoburgesshill Ltd | Burgess Hill | 2016 |
| Athletics Northern Ireland (2008) | Belfast | 2006 |
| Athletismo Ltd | London | 2019 |
| Athletix Kidz Limited | Reigate | 2016 |
| Athlin Limited | West Malling | 2023 |
| Athlon Fitness Herts Limited | Ware | 2018 |
| Athltiq Ltd | Huddersfield | 2025 |
| Athlyn Ltd | London | 2020 |
| Athol Wellness Limited | Swansea | 2026 |
| Atholl Country Life Museum | Pitlochry | 2004 |
| Atholl Sporting Limited | Perth | 2023 |
| Athoria Ltd | Southsea | 2023 |
| Athos Art Ltd | Middlesbrough | 2022 |
| Aththnayaka Dance and Wedding Services Ltd | Watford | 2018 |
| Athurst Digital Ltd | Barnstaple | 2023 |
| Aticavo Textile Conservation Limited | Sidcup | 2022 |
| Atilla INK Tattoo Limited | Bath | 2026 |
| ATK Assets Limited | Market Harborough | 2024 |
| Atkda Ltd | Sutton Coldfield | 2022 |
| Atkfilm Ltd | London | 2022 |
| Atkin Padel Ltd | Hull | 2025 |
| Atkins Promotions Limited | Wolverhampton | 2012 |
| Atkinson Fine Arts Ltd | Ilkley | 2022 |
| Atkotron Ltd | Maidstone | 2019 |
| ATL Leisure Limited | Eccleshall | 2003 |
| Atlam Design Worldwide Limited | Henley-In-Arden | 1996 |
| Atlanta Entertainments Agency Ltd | Ilkeston | 2001 |
| Atlanta Limited | Stevenston | 2003 |
| Atlantic Agents Limited | London | 2021 |
| Atlantic Amusements Limited | London | 1971 |
| Atlantic Challenge (Scotland) | Forres | 1998 |
| Atlantic Dash Ltd | London | 2021 |
| Atlantic Events NE Ltd | Middlesbrough | 2017 |
| Atlantic Jaxx Recordings Limited | London | 2005 |
| Atlantic Leisure Limited | | 1972 |
| Atlantic Racquet Centre | Bideford | 2011 |
| Atlantic Rally for Cruisers Limited | Isle Of Wight | 2002 |
| Atlantic Screen Composers Limited | Pewsey | 2010 |
| Atlantic Scuba Ltd | Doncaster | 2024 |
| Atlantic Seven Productions Limited | Croydon | 1984 |
| Atlantic SME Ltd | Beccles | 2013 |
| Atlantic Sports SL Ltd | St. Albans | 2023 |
| Atlantic Television Limited | London | 1997 |
| Atlantis Marine Holdings Ltd | London | 2025 |
| Atlantis Music Associates Ltd | London | 2024 |
| Atlantis Soft Play Limited | Grimsby | 2019 |