| Attic Theatre Limited | Glastonbury | 1974 |
| Attic Theatre School Ltd | Nottingham | 2021 |
| Attic Thing Records Ltd | Fitzrovia | 2024 |
| Attica Gambling Limited | Aylesbury | 2011 |
| Atticist Productions Ltd | Banbury | 2019 |
| Atticus Jones Limited | London | 2019 |
| Atticus KIM Ltd | Droitwich | 2023 |
| Atticus Productions Limited | Middlesex | 2010 |
| Attika Fine Arts Ltd | London | 2019 |
| Attiki Art Limited | Caterham | 2022 |
| Attinis Ltd | London | 2024 |
| Attitude 2 Art Ltd | London | 2018 |
| Attitude Aerobatics Limited | Reading | 2008 |
| Attitude Airsports Ltd | Thornton Cleveleys | 2016 |
| Attitude Dance School Ltd | Abingdon | 2022 |
| Attitude Dance Studios Ltd | Bootle | 2019 |
| Attitude Festival Ltd | Exeter | 2022 |
| Attitude Fitness Limited | Hillsborough | 2026 |
| Attitude IS Everything | London | 2007 |
| Attitudes to Life Records Ltd | Liverpool | 2019 |
| Attproductions Ltd | Northampton | 2024 |
| Attracktion Limited | Loughborough | 2025 |
| Attraction Solutions Ltd | Witham | 2025 |
| Attune Theatre CIC | Paisley | 2012 |
| Attune YOU Ltd | Airdrie | 2023 |
| Attwater Racing Limited | Epsom | 2008 |
| Attwood Leisure Limited | Exeter | 2018 |
| Attwoolls Ltd | Whitstable | 2024 |
| ATU Limited | Walsall | 2016 |
| ATW Lifestyle Ltd | Wedmore | 2025 |
| ATW Records Ltd | London | 2023 |
| Atwal Fitness Ltd | Guildford | 2022 |
| Atypical Creative Ltd | London | 2025 |
| Atypical Works Ltd | Bishop'S Stortford | 2020 |
| AU Sports Ltd | Redditch | 2013 |
| Aube Production Ltd | London | 2021 |
| Auberies Estate Sporting Limited | Sudbury | 2023 |
| Aubrey Creative Limited | Romford | 2023 |
| Auburn Design Limited | Westbury | 2007 |
| Auc.Art Ltd | Hampshire | 2016 |
| Auchterarder Gymnastics Trust | Perthshire | 1993 |
| Auckland Youth and Community Centre Limited | Bishop Auckland | 2006 |
| Aucm Limited | Feltham | 2017 |
| Aucott Interior Design Limited | Ferndown | 2011 |
| Auction House Redruth CIC | Redruth | 2024 |
| Aucto Visio Ltd | Sunderland | 2025 |
| Audacious Creative Communications Limited | Bromsgrove | 2012 |
| Audacious Entity Ltd | Shoeburyness | 2023 |
| Audacious Media Limited | Watford | 2025 |
| Audaciousink Limited | Slough | 2025 |
| Audacity Events Limited | Burntwood | 2025 |
| Audax United Kingdom Long Distance Cyclists` Association | Hatfield Peverel | 2006 |
| Audere Talent Management Limited | Aylesbury | 2018 |
| Audiama Studios Limited | London | 2022 |
| Audience Labs Ltd | Tunbridge Wells | 2022 |
| Audio and Communication Technology Limited | Chester | 2013 |
| Audio Assassins Limited | Sutton | 2017 |
| Audio Cartel Limited | Norwich | 2018 |
| Audio Description Services Ltd | Eastbourne | 2024 |
| Audio Enterprise Limited | Stockport | 2018 |
| Audio Farm Ltd | Norwich | 2016 |
| Audio Feed Ltd | Bournemouth | 2003 |
| Audio Garden Ltd | London | 2024 |
| Audio Glasgow CIC | Glasgow | 2026 |
| Audio Guys Glasgow Ltd | Paisley | 2024 |
| Audio Integer Limited | Nottingham | 2000 |
| Audio Interface Ltd | Southampton | 2024 |
| Audio Logical Group Limited | Bristol | 2015 |
| Audio London Ltd | London | 2026 |
| Audio Mechanix Ltd | London | 2025 |
| Audio Nugget Limited | London | 2017 |
| Audio Play Research Ltd | Edgware | 2024 |
| Audio Religion Music Ltd | Belfast | 2014 |
| Audio Visia AV Ltd | Bradford | 2025 |
| Audio Visual Arts Limited | Nottingham | 1987 |
| Audio Wallet Ltd | London | 2024 |
| Audio Works Rehearsal Studios Ltd | Northampton | 2024 |
| Audio.Sync CIC | London | 2023 |
| Audiobeat Limited | Oldham | 1989 |
| Audiobook Narration UK Limited | Harpenden | 2026 |
| Audiophile Limited | Maidenhead | 2003 |
| Audiophonic Limited | London | 2009 |
| Audiotube Limited | Caterham | 2006 |
| Audious Ltd | Yateley | 2019 |
| Audiozone WF1 Arts and Media Ltd | Wakefield | 2021 |
| Audition Oracle Limited | St Albans | 2015 |
| Audition Ready and Events and Education Ltd | Tunbridge Wells | 2024 |
| Audition Ready Limited | Tunbridge Wells | 2020 |
| Audley Centre CIC | Blackburn | 2017 |
| Audrey Competitions Limited | Leicester | 2024 |
| Audrey Kawasaki Limited | Lowestoft | 2023 |
| Audrey Productions Ltd | Painswick | 2019 |
| Audrey Spencer School of Theatre Dance Limited | Huddersfield | 2014 |
| Audry PR1 Ltd | Preston | 2023 |
| Auger Collective CIC | Bournemouth | 2024 |
| Aughabrack & District Community Association | Strabane | 2004 |
| Aughlisnafin Community Association | Castlewellan | 2013 |
| Aughnacloy Sports Development Association Ltd | Aughnacloy | 2026 |
| Aughton Institute Limited (the) | Ormskirk | 1907 |
| Aughton Lawn Tennis Club Limited | Ormskirk | 2021 |