| Assetmarketcap Ltd | London | 2024 |
| Assetmesh Ltd | Hornchurch | 2026 |
| Assetminder (Operations) Limited | Sheffield | 2024 |
| Assetminder Limited | Sheffield | 2024 |
| Assetnest Limited | London | 2023 |
| Assetops Ltd | London | 2025 |
| Assetpass Ltd | London | 2021 |
| Assetq Limited | Kingston Upon Thames | 2012 |
| Assetra Systems Ltd | London | 2025 |
| Assets 365 Limited | Cardiff | 2020 |
| Assetscape Limited | Bourne | 2014 |
| ASSETSPHERES@19 Ltd | Enfield | 2019 |
| Assetspire Limited | Norwich | 2011 |
| Assetsview Limited | London | 2022 |
| Assettag Technologies Ltd | London | 2026 |
| Assettekno Limited | London | 2020 |
| Assettrac Limited | Brighton | 1999 |
| Assetvault Limited | Hounslow | 2016 |
| Assetware Limited | Harpenden | 1987 |
| Assetwave Consulting Ltd | Doncaster | 2024 |
| Assetworks Fleet Solutions Ltd | Derby | 2023 |
| Assetworx Ltd | Aberdeen | 2023 |
| Assidian Limited | Chessington | 2003 |
| Assidium Registry Limited | Billingshurst | 2023 |
| Assiduous Global Ltd | Coventry | 2016 |
| Assiduous Productions Ltd | Hebden Bridge | 2021 |
| Assiduous-It Ltd | Edinburgh | 2012 |
| Assif Ltd | Manchester | 2019 |
| Assign Systems Limited | Dorset | 1995 |
| Assign-It Limited | Hatfield | 2001 |
| Assignment Media Ltd | Burton-On-Trent | 2010 |
| Assilium Limited | Rugby | 2020 |
| Assima R&D UK Limited | Manchester | 2010 |
| Assima UK Limited | Bolton | 2003 |
| ASSIMIL8 Limited | Northampton | 2006 |
| Assimilate Systems Ltd. | Dereham | 2013 |
| Assir Consultancy Limited | Canterbury | 2025 |
| Assist AI Ltd | Truro | 2026 |
| Assist AID Ltd | Milton Keynes | 2024 |
| Assist Business IT Ltd | Salisbury | 2014 |
| Assist Connect Ltd | London | 2026 |
| Assist Digital EU Limited | Ipswich | 2004 |
| Assist Iron Flight Ltd | Glasgow | 2025 |
| Assist IT Solutions Limited | Doncaster | 2007 |
| Assist MI Ltd | Newcastle Upon Tyne | 2010 |
| Assist Research Ltd | Cranleigh | 2019 |
| Assist Software Test Management Limited | Hayling Island | 2007 |
| Assist Solutions Limited | Wigan | 2009 |
| Assist Solutions Software Limited | Skelmersdale | 2010 |
| Assist Telecommunications Ltd | London | 2025 |
| Assist Transit Global Limited | Gillingham | 2023 |
| Assistance Routière Paiement Ltd | London | 2025 |
| Assistant Engine Ltd | London | 2025 |
| Assistant Rose Ltd | London | 2023 |
| Assistbda Ltd | Coalville | 2026 |
| Assisted Conversions Ltd | Whitehills Business Park | 2016 |
| Assisted Discovery Limited | St Neots | 2019 |
| Assisted Solutions Limited | Rickmansworth | 2024 |
| Assisted. Ltd | Lutterworth | 2016 |
| Assistemia Ltd | London | 2025 |
| Assisterr Ltd | London | 2023 |
| Assistiv CIC | Halifax | 2018 |
| Assistiv Systems Ltd | Faversham | 2026 |
| Assistive Fintech LAB Limited | Bristol | 2025 |
| Assistive Partner Limited | London | 2006 |
| Assistive Solutions Ltd | London | 2009 |
| Assistivo Limited | London | 2025 |
| Assisto Consulting Ltd | London | 2016 |
| Assistquik Ltd | Manchester | 2025 |
| Assisttec Limited | St Neots | 2007 |
| Assiz Ltd | London | 2026 |
| Assl Consulting Ltd | London | 2025 |
| Assmbl.Ai Limited | Bury St Edmunds | 2023 |
| Asso Technologies Ltd | Salford | 2026 |
| Assoc.One Ltd | London | 2026 |
| Associate Computer Services Limited | Sleaford | 1997 |
| Associate Enterprises Limited | London | 2002 |
| Associate Films Limited | Worthing | 2014 |
| Associate Planet Limited | Haywards Heath | 2011 |
| Associate Software Limited | Essex | 2007 |
| Associated 2 Digital UK Ltd | Walton-On-Thames | 2021 |
| Associated Artists Ltd | London | 2018 |
| Associated Board of the Royal Schools of Music (Publishing) Limited(The) | London | 1985 |
| Associated Brands UK Limited | Hailsham | 2006 |
| Associated British Picture Corporation Limited | Deal | 2023 |
| Associated Business Services Ltd | Belfast | 1998 |
| Associated Computer Services Ltd | Worcester | 2021 |
| Associated Consultants Limited | Bridgend | 1989 |
| Associated Data Developments Limited | Essex | 1998 |
| Associated Designs (UK) Limited | Suffolk | 2002 |
| Associated Dynamics Systems Limited | Tring | 1987 |
| Associated Educational Technologies Ltd | Newcastle Upon Tyne | 2014 |
| Associated Experts Ltd | Towcester | 2018 |
| Associated Interim Management Limited | Dartford | 2000 |
| Associated Ltd | Kidlington | 2024 |
| Associated Mess Ltd | London | 2021 |
| Associated Music International (Holdings) Limited | | 1990 |
| Associated Music International Limited | | 1995 |
| Associated Networks (UK) Limited | Cobham | 2002 |
| Associated Newspapers Limited | London | 1905 |