| Attapoll Ltd | London | 2016 |
| Attar Technologies Limited | Hayes | 2015 |
| Attard Consulting Ltd | London | 2022 |
| Attaro Limited | Nantwich | 2018 |
| Attasiaa Media Ltd | Greenford | 2024 |
| Attech Consulting Limited | London | 2015 |
| Attekus UK Ltd | Manchester | 2025 |
| Attelas Managed AI Limited | London | 2023 |
| Attellsoft Limited | Ipswich | 2021 |
| Attempero Limited | Hinckley | 2017 |
| Attempt Solutions Limited | Reading | 2023 |
| Attempt Studios Ltd | Brighton | 2022 |
| Attempted Murder Games Ltd | London | 2025 |
| Attempting Technology Limited | Wisbech | 1998 |
| Attenborough Productions Limited | Milton Keynes | 2016 |
| Attenborough Software Limited | Nottingham | 1994 |
| Attenbroke Ltd | St. Ives | 2020 |
| Attend 2 IT Limited | Buntingford | 2009 |
| Attend Technologies Ltd | London | 2025 |
| Attender Ltd | Margate | 2018 |
| Attendist Ltd | Manchester | 2021 |
| Attendit.Io Ltd | Rugeley | 2021 |
| Attendite Ltd | Milton Keynes | 2019 |
| Attendzen Limited | London | 2022 |
| Attention Deficit Music & Media Limited | Westcliff-On-Sea | 2025 |
| Attention Economics Consulting Ltd | London | 2021 |
| Attention First Ltd | Wallingford | 2026 |
| Attention Game Ltd | London | 2024 |
| Attention Holdings Ltd | London | 2025 |
| Attention Layer Consulting Ltd | Cheadle | 2011 |
| Attention One Ltd | London | 2024 |
| Attention to Retail Limited | Northwich | 2011 |
| Attentional Ltd. | Bristol | 1990 |
| Attentionit Limited | Manchester | 2007 |
| Attentive Mobile UK Ltd | Birmingham | 2021 |
| Attentive Records Limited | Worthing | 2011 |
| Attentivics Ltd | Edinburgh | 2016 |
| Attentix Ltd | London | 2024 |
| Attentoit Ltd | Bristol | 2017 |
| Attentus Group Ltd | Kent | 2007 |
| ATTENU8 Ltd | Kings Lynn | 2003 |
| Attenxion Ltd | London | 2024 |
| Attercop Ltd | Brighton | 2022 |
| Attergirl Productions Ltd | Birmingham | 2025 |
| Attermire Consulting Limited | Settle | 2017 |
| Atters Picture Company Ltd | Banbury | 2011 |
| Atterton Productions Limited | Royston | 2016 |
| Attest Design Ltd | London | 2024 |
| Attest Digital Ltd | Chesterfield | 2020 |
| Attest Technologies Limited | London | 2015 |
| Attesta Limited | London | 2026 |
| Attestant Limited | London | 2020 |
| Attestari Holdings Ltd | Weston-Super-Mare | 2026 |
| Attestari Immutis Ltd | Weston-Super-Mare | 2026 |
| Attestive Ltd | London | 2026 |
| Attestly Ltd | London | 2026 |
| Attft Limited | Coventry | 2023 |
| Attg Ltd | Manchester | 2022 |
| Attheraces Limited | London | 1999 |
| Attic Entertainment Ltd | London | 2013 |
| Attic Film Services Ltd. | London | 2026 |
| Attic Games & Entertainment Limited | Warminster | 1997 |
| Attic London Ltd | Watford | 2011 |
| Attic Media (Midlands) Ltd | Derby | 2018 |
| Attic Music Group Limited | Ashton-Under-Lyne | 2021 |
| Attica Cybernetics Limited | London | 2024 |
| Attica Data Services Limited | London | 2005 |
| Attica Publishing Ltd | Ellesmere | 2020 |
| Attica Records Limited | Shropshire | 2003 |
| Attici Group Limited | London | 2020 |
| Atticmedia Limited | Brentwood | 2010 |
| ATTICO2 Limited | Whitehills Business Park | 2012 |
| Atticus 7 Limited | Woking | 2012 |
| Atticus Associates Ltd | London | 2007 |
| Atticus Connect Limited | Dorchester | 2017 |
| Atticus Film & Television Limited | Brighton | 2015 |
| Atticus Finch Group Limited | Telford | 2024 |
| Atticus Finch Limited | London | 2004 |
| Atticus Information Technology Solutions Limited | Washington | 2007 |
| Atticus Intelligence Ltd | London | 2024 |
| Atticus International Limited | Lewes | 2016 |
| Atticus LEX Ltd | Devizes | 2024 |
| Atticus Software Solutions Limited | London | 2011 |
| Atticus Technology Ltd | Liverpool | 2011 |
| Attiendo Limited | London | 2013 |
| Attifin AI Ltd | Newcastle Upon Tyne | 2025 |
| Attikas Ltd | Bracknell | 2008 |
| Attila Books Ltd | Newcastle Upon Tyne | 2025 |
| Attimo AI Ltd | London | 2026 |
| Attimo Technologies Ltd | London | 2025 |
| Attingham Education Limited | Dudley | 2020 |
| Attio Limited | London | 2017 |
| Attire Collective Limited | London | 2026 |
| Attis Capital Ltd | Gloucester | 2022 |
| Attis Fitness Limited | Paisley | 2016 |
| Attis Technology Limited | Weybridge | 2017 |
| Attitude Group Ltd | Reading | 2023 |
| Attix AI UK Limited | London | 2022 |
| ATTIX5 UK Limited | Reading | 2001 |
| Attlas Group Ltd | London | 2022 |