| Alcj & Co Ltd | Wembley | 2021 |
| Alcj Consultancy Limited | Ilford | 2023 |
| Alclemie Architectural Consulting Ltd | Preston | 2018 |
| Alclin (PTY) UK Ltd | Bedford | 2015 |
| Alclin (UK) Limited | Chessington | 2010 |
| Alclutha Consulting Limited | Dumbarton | 2022 |
| Alcm Consulting Ltd | Maidenhead | 2023 |
| Alcm Limited | Armagh | 2018 |
| Alcmaeon Medical Communications Ltd | Guildford | 2013 |
| Alcn Consulting Ltd | Brentwood | 2026 |
| Alco Group (South East) Ltd | Godalming | 2025 |
| Alco Project & Construction Management Limited | Canterbury | 2025 |
| Alco Support Services Ltd | Manchester | 2023 |
| Alcoa Services UK Limited | Bristol | 2025 |
| Alcobev Limited | London | 2019 |
| Alcock Architecture Ltd | Bromsgrove | 2025 |
| Alcocks Lane Limited | Tadworth | 2005 |
| Alcocks Property Lawyers Limited | Nottingham | 2009 |
| Alcohol & Crime Reduction Consultancy Limited | Chandlers Ford | 2012 |
| Alcohol Ltd | Cheltenham | 2003 |
| Alcohols (North West) Limited | Rugby | 1995 |
| Alcolase Limited | London | 2026 |
| Alcolizer Technology United Kingdom Limited | Gateshead | 2006 |
| Alcom Renewables UK Limited | London | 2021 |
| Alcon BSL Services Ltd | Romford | 2021 |
| Alcon EYE Care UK Limited | Camberley | 1964 |
| Alcon Limited | Birmingham | 2001 |
| Alcon Maddox Ltd | London | 2023 |
| Alcon Precision Engineering Limited | London | 2007 |
| Alconbury Capital Ltd | Richmond | 2025 |
| Alconbury Consulting Ltd | London | 2018 |
| Alconbury Operations Ltd | Richmond | 2025 |
| Alcor Reliance Ltd | Wilmslow | 2019 |
| Alcorn Ltd. | Radlett | 2002 |
| Alcorp Limited | Chislehurst | 2016 |
| Alcorstar Ltd | London | 2018 |
| Alcorum | Wigan | 2025 |
| Alcott Solicitors Limited | London | 2014 |
| Alcou Ltd | Congleton | 2023 |
| Alcova Ltd | London | 2024 |
| Alcove Architecture Ltd | Southwick | 2013 |
| Alcr Ltd | Enfield | 2022 |
| Alcra Ltd | London | 2022 |
| Alcs Consultancy Ltd | Tamworth | 2022 |
| Alcuin Advisors Ltd | London | 2017 |
| Alculus Ltd | London | 2023 |
| Alcuris Ltd | Loughborough | 2015 |
| Alcyon Capital Limited | London | 2012 |
| Alcyon Media Ltd | Bedford | 2014 |
| Alcyone International Limited | London | 2019 |
| Alcyone Law Ltd | London | 2026 |
| Alcyoneus Consulting Limited | Pontypool | 2026 |
| Alcyra Limited | London | 2024 |
| ALD Business Services Ltd | Lancashire | 2007 |
| ALD Consulting Ltd | Glasgow | 2026 |
| ALD Jackom Limited | Cardiff | 2021 |
| ALD Projects Ltd | Wimborne | 2025 |
| Alda Capital Limited | Marlow, | 2004 |
| Aldaba Limited | London | 2014 |
| Aldama CAD Services Limited | Aberdeen | 2008 |
| Aldan Management Limited | London | 2002 |
| Aldan Solutions Limited | Gosport | 2006 |
| Aldane Advisory Ltd | Warrington | 2026 |
| Aldanex Limited | Sheffield | 2022 |
| Aldap Ltd | Ilkley | 2021 |
| Aldarton Limited | Milton Keynes | 2009 |
| Aldatum Limited | | 1995 |
| Aldawlya Consultancy Law Firm Ltd | Dagenham | 2026 |
| Aldborough and Boroughbridge Agricultural Show Limited | Tadcaster | 2014 |
| Aldbourne Limited | Salisbury | 2011 |
| Aldburg SA Ltd | London | 2020 |
| Aldbury Directors Limited | Milton Keynes | 1996 |
| Aldbury Limited | Milton Keynes | 2004 |
| Aldbury Secretaries Limited | Milton Keynes | 1996 |
| Aldcroft Welding Services Limited | Bury | 2012 |
| Alde Interiors Limited | Woodbridge | 2024 |
| Aldea Bella (NO 34) Limited | Hamilton | 1984 |
| Aldea Bella (NO 36) Limited | Glasgow | 1984 |
| Aldea Bella (NO 38) Limited | Bishopbriggs | 1984 |
| Aldea Bella (NO. 50) Limited | Edinburgh | 1988 |
| Aldea Blanca 1 Limited | Bromsgrove | 2002 |
| Aldea Creatives Limited | Watford | 2026 |
| Aldea Projects Ltd | London | 2026 |
| Aldea Property Limited | Kirkcaldy | 1994 |
| Aldean Construction Services Ltd | Alcester | 2020 |
| Aldebaran Consultants Limited | Co Tyrone | 2002 |
| Aldebaran Limited | Romsey | 2025 |
| Aldebaran Trading Ltd | London | 2021 |
| Aldeburgh Design Limited | Saxmundham | 2006 |
| Aldeburgh Vets Ltd | Woodbridge | 2020 |
| Aldeby Shot Blasting Limited | Leicester | 1989 |
| Aldeia Impact Advisory Ltd | London | 2025 |
| Aldeia International Limited | Cranbrook | 2020 |
| Aldel Ltd | London | 2017 |
| Aldemir-Down Ltd | Norwich | 2023 |
| Alden Accountancy Services Limited | Newmarket | 2000 |
| Alden Accountants Ltd | Lancing | 2011 |
| Alden Advisers Limited | London | 2018 |
| Alden Bethell Advisory Limited | Wimborne | 2016 |
| Alden Business Consultancy Ltd | Kington | 2025 |