| Associated North West Media Ltd | Oldham | 2021 |
| Associated Press Limited(The) | London | 1931 |
| Associated Press Television News Limited | London | 1998 |
| Associated Recordings Company Ltd | Weybridge | 2014 |
| Associated Rediffusion Productions Limited | York | 1990 |
| Associated Technical Services Ltd | Epping | 2014 |
| Associated Technology Pipeline Limited | Basingstoke | 1998 |
| Associated Telecom Limited | Telford | 1994 |
| Associated Television Limited | London | 2005 |
| Associated Utility Services Ltd | Tadley | 2024 |
| Associates in Advertising Limited | London | 1986 |
| Associatethis Limited | Thame | 2005 |
| Association for AI in Financial Services CIC | Bromsgrove | 2025 |
| Association for Central Asian Civilizations & Silk Road Studies | London | 2014 |
| Association for Key Account Management Limited | Ashford | 2024 |
| Association for Prisoners Maintaining Innocence | Horsham | 2025 |
| Association of Chartered Physiotherapists in Neurology | Newport | 2017 |
| Association of Computer Engineers | Cranbrook | 2005 |
| Association of Drainage Authorities | Kenilworth | 2014 |
| Association of Retained Council Housing Limited | Coventry | 2012 |
| Association of Scientists, Developers and Faculties | London | 2017 |
| Associative Data Services Limited | London | 2019 |
| Associative Limited | Oxford | 2025 |
| Associative Trails Limited | Ramsgate | 2005 |
| Associo Ltd | Richmond | 2018 |
| Assonance Limited | London | 2024 |
| Assorted Images Limited | London | 2014 |
| Assosia Ltd | Brentwood | 2003 |
| Assunto Ltd | London | 2018 |
| Assur Limited | Reading | 2011 |
| Assur.Ai Ltd | London | 2026 |
| Assura IQ Ltd | Northampton | 2026 |
| Assura Safety Limited | Falmouth | 2026 |
| Assura Systems Ltd | London | 2026 |
| Assurance Circle Limited | Gravesend | 2026 |
| Assurant Ltd | Pontefract | 2018 |
| Assurdeal Ltd | Charing | 2015 |
| Assurdly UK Limited | Ruislip, | 2024 |
| Assure APM Limited | Edinburgh | 2014 |
| Assure Axis Ltd | London | 2026 |
| Assure Claims Ltd | Sutton | 2023 |
| Assure CTX Limited | New Malden | 2026 |
| Assure Pass Limited | Winchester | 2009 |
| Assure Sense Ltd | Swansea | 2022 |
| Assure Service Solutions Limited | Wimborne | 2014 |
| Assure Start Consultancy Ltd | Stockport | 2021 |
| Assure Start Ltd | Kirkcaldy | 2024 |
| Assure Techsol Ltd | Reading | 2026 |
| Assure Testing Limited | Altrincham | 2025 |
| ASSURE24 Limited | Halifax | 2010 |
| Assured (APS) Limited | Worcester Park | 2014 |
| Assured AI Digital Ltd | London | 2025 |
| Assured AV Ltd | Stone | 2024 |
| Assured Aviation Consulting Limited | Malvern | 2022 |
| Assured Clarity Limited | Altrincham | 2013 |
| Assured Communications (Leicester) Ltd | Leicester | 2011 |
| Assured Computer Solutions Limited | Uxbridge | 2002 |
| Assured Computing Ltd | Blackpool | 2022 |
| Assured Consulting Limited | Cardiff | 2024 |
| Assured Contacts Ltd | Margate | 2025 |
| Assured Data Protection Limited | Leeds | 2016 |
| Assured Data Services Ltd | Cardiff | 2019 |
| Assured Design Ltd | Leicester | 2020 |
| Assured Digital Technologies Limited | Bristol | 2020 |
| Assured Enterprise Technology Limited | Swindon | 2008 |
| Assured Finance Today Ltd | Berwick-Upon-Tweed | 2013 |
| Assured Gain Consulting Ltd | London | 2022 |
| Assured Information Security Limited | London | 2010 |
| Assured Information Systems Limited | St Neots | 1996 |
| Assured Innovations Limited | North Shields | 2011 |
| Assured Interest Limited | Birmingham | 2019 |
| Assured IT Consulting Ltd | London | 2020 |
| Assured IT Group Ltd | Harlow | 2026 |
| Assured IT Ltd | Darwen | 2019 |
| Assured IT Services Ltd | Lyndhurst | 2021 |
| Assured IT Solutions Limited | Norwich | 2016 |
| Assured Network Solutions Limited | Stevenage | 2021 |
| Assured Searches Ltd | Bristol | 2003 |
| Assured Service Delivery Limited | Ashford | 2022 |
| Assured Solutions Communications (ASC) Ltd | Preston | 2026 |
| Assured Solutions Services Limited | Maidstone | 2015 |
| Assured Systems (UK) Ltd | Stone | 2011 |
| Assured Tech Ltd | Great Yarmouth | 2023 |
| Assured Telecoms Limited | Buckie | 2015 |
| Assured Thought Limited | London | 2004 |
| Assured Time Ltd | Gloucester | 2021 |
| Assured Travel Solutions Ltd | Bristol | 2014 |
| Assuredcheck Ltd | Birmingham | 2026 |
| Assuredly Tech Consultancy Ltd | Dover | 2023 |
| Assuredtalk Limited | Chorley | 2024 |
| Assureful Ltd | London | 2021 |
| Assurelabs Ltd | Chelmsford | 2023 |
| Assurelogic Ltd | Tilbury | 2026 |
| Assurelogic Solutions Ltd | Wimborne | 2025 |
| Assureops Ltd | Newcastle Upon Tyne | 2026 |
| Assurepath Ltd | Manchester | 2025 |
| Assurepoint Advisory Ltd | Stockport | 2026 |
| Assurestack Ltd | Wallington Surrey | 2022 |
| Assurestack Solutions Limited | Wallington | 2023 |
| Assurestor Limited | Grays | 2012 |