| Assisstar Ltd | Prescot | 2019 |
| Assist Engineering Limited | Newstead Village | 2001 |
| Assist EV Limited | Kenilworth | 2021 |
| Assist Hygiene Products Ltd | Bromborough | 2006 |
| Assist Solutions (UK) Limited | Chertsey | 2009 |
| Assist Your Lift Ltd | Northampton | 2020 |
| Assista Industry Ltd | Blackett Street Manchester | 2026 |
| Assistant Group Ltd | London | 2019 |
| Assisted Intelligence Ltd | Edinburgh | 2024 |
| Assistify Autonomous Ltd | South Croydon | 2026 |
| Assmann Office Furniture Ltd. | London | 2020 |
| Associate Engineering Systems Limited | Dungannon | 1991 |
| Associate Interior Solutions Ltd | Halesowen | 2008 |
| Associated Agencies Limited | Witney | 1993 |
| Associated Bonded Cables Limited | Merseyside | 1990 |
| Associated British Motorcycles Ltd | Glasgow | 2018 |
| Associated Casing Co. Limited | Haverhill | 1971 |
| Associated Catering Equipment Limited | Peterborough | 2022 |
| Associated Control Systems Limited | Wolverhampton | 1998 |
| Associated Dental Products Limited | Purton | 1937 |
| Associated Electrical Limited | Bromsgrove | 2005 |
| Associated Group Services Limited | Ongar | 2000 |
| Associated Instruments Repairs Limited | Bournemouth | 1997 |
| Associated Joinery Techniques Limited | London | 1967 |
| Associated Laboratories Limited | Wallington | 2004 |
| Associated Maintenance Services Ltd | Barnard Castle | 2014 |
| Associated Metalmasters Limited | Dudley | 2012 |
| Associated Pallets Holdings Limited | Southampton | 2024 |
| Associated Pallets Limited | Southampton | 1992 |
| Associated Plastic Components Limited | Hull | 1993 |
| Associated Pneumatic Industries Limited | Stoke-On-Trent | 2024 |
| Associated Processors Limited | Belfast | 1984 |
| Associated Recycling Equipment Limited | Enfield | 2025 |
| Associated Security Solutions Limited | Manchester | 2011 |
| Associated Signs and Graphic Design Ltd | Doncaster | 2009 |
| Associated Smoke & Fire Products Limited | Penarth | 2023 |
| Associated Steel Products Limited | Newcastle Under Lyme | 2007 |
| Associated Tapchangers Limited | Harlow | 2013 |
| Associated Technology Services Limited | Clevedon | 1994 |
| Associated Utility Supplies Limited | Hudderfield | 1998 |
| Associated Western Limited | Cardiff | 1947 |
| Assos Kitchen Ltd | Cardiff | 2024 |
| Assp Ltd | Oldham | 2019 |
| Assumed Form Ltd | Crawley | 2021 |
| Assunta French Ltd | London | 2022 |
| Assurance Testing Services Ltd | Bellshill | 2025 |
| Assure Catering Engineers Ltd | Motherwell | 2019 |
| Assure Property and Design Ltd | Northampton | 2026 |
| Assured Asset Energy Limited | Leamington Spa | 2012 |
| Assured Contractors Limited | Basildon | 2012 |
| Assured Corporate Limited | Pitstone | 2021 |
| Assured Electrical (Installation and Testing) Limited | Stoke-On-Trent | 2014 |
| Assured Energy Performance (Global) Ltd | Holmes Chapel | 2020 |
| Assured Equipment Services Limited | Shrewsbury | 2018 |
| Assured Fine Furniture Limited | Manchester | 2003 |
| Assured Packaging Limited | Stoke-On-Trent | 2009 |
| Assured Passive Fire Protection Limited | Ilkeston | 2010 |
| Assured Product Solutions Ltd | London | 2015 |
| Assured Sleep Ltd | Sunderland | 2021 |
| Assured Solutions Limited | Swadlincote | 1988 |
| Assured Stairlifts Limited | Keighley | 2005 |
| Assured Tech Conglomerate Ltd | Kidwelly | 2025 |
| Assurefit Ltd | Birmingham | 2025 |
| Assuwa Ltd | London | 2022 |
| Assynt Tweed CIC | By Lairg | 2026 |
| Assyst Bullmer Limited | Wakefield | 1987 |
| AST Digital Solutions Ltd | Swindon | 2019 |
| AST Furniture Limited | Dewsbury | 2024 |
| AST Heating Limited | Leven | 2014 |
| Asta Aeronautic Support Ltd | Cambridge | 2024 |
| Astabridge (Holdings) Limited | Corby | 2007 |
| Astabridge Group Limited | Corby | 2024 |
| Astabridge Limited | Corby | 1989 |
| Astaf Services Ltd | Southampton | 2013 |
| Astan Renewable Energy Ltd | Stone | 2010 |
| Astar Carpenters Limited | Chichester | 2017 |
| Astarbox Ltd | Weybridge | 2024 |
| Astarra Ltd | Darlington | 2018 |
| Astec Conveyors Limited | Derby | 2001 |
| Astec Digital UK Ltd | London | 2021 |
| Astec Industries Europe Limited | Co Tyrone | 2001 |
| Astec Precision Limited | Ulverston | 1998 |
| Astec Solar Solutions Ltd | Barwell | 2025 |
| Astech Electronics Limited | Binsted | 1974 |
| Astech Engineering Services Ltd | Knottingley | 2014 |
| Astech Interiors Limited | Enfield | 2002 |
| Asteelflash (Bedford) Limited | Bedford | 1987 |
| Astell Scientific Limited | Kent | 1950 |
| Astemo UK, Ltd. | Bolton | 1997 |
| Aster Catering Ltd | Kingston Upon Thames | 2023 |
| Aster Cottage Limited | Braintree | 2024 |
| Aster Legacy Ltd | Camberley | 2025 |
| Asterion PI Ltd | Exeter | 2023 |
| Asterisk Direct Limited | Chorley | 2004 |
| Asterisk Lifesciences Ltd | London | 2014 |
| Asterix Electrical Services Limited | Lichfield | 2019 |
| Asterley Bros, London Ltd | London | 2014 |
| Astermon U.K. Company Ltd. | Beckenham | 2025 |
| Asteroid Carpentry Ltd | Welham Green | 2024 |
| Asteroid Mining Corporation Limited | Manchester | 2016 |