| Aleks Holding Ltd | London | 2025 |
| Aleksander Maniowski Ltd | London | 2018 |
| Aleksha Holdings Ltd | Rochester | 2024 |
| Aleksma Group Ltd | London | 2024 |
| Alem Holdings Limited | Chippenham | 2019 |
| Alemara Limited | Altrincham | 2022 |
| Alemax Capital Limited | Chobham | 2024 |
| Aleo Group Ltd | Bedford | 2026 |
| Aleon Holdings Limited | London | 2025 |
| Aleph Capital Partners Limited | London | 2022 |
| Aleph Commodities Ltd | London | 2018 |
| Aleph Eins Capital Ltd | London | 2026 |
| Aleph FIN C Ltd | London | 2022 |
| Aleph Finance Ltd | London | 2023 |
| Aleph International Holdings (UK) Ltd | London | 2022 |
| Aleph Intertank Limited | London | 2022 |
| Aleph Investment II Ltd | Bath | 2018 |
| Aleph Investment Ltd | Bath | 2013 |
| Alephco Developments Limited | London | 2017 |
| Alera Holdings Ltd | Tonbridge | 2026 |
| Alere Healthcare Limited | Weston-Super-Mare | 2025 |
| Alere Properties Limited | Weston-Super-Mare | 2025 |
| Aleris Holdings Ltd | London | 2026 |
| Aleron Holdings Limited | Milton Keynes | 2019 |
| Alert Bay Investment Company | Kendal | 1934 |
| Alert Communications (Holdings) Limited | London | 1999 |
| Alert Electrical Wholesalers Holdings Limited | Nottingham | 2010 |
| Alert Holdings Ltd | Mansfield | 2026 |
| Alert INS Limited | Daventry | 2026 |
| Alert Media UK Limited | London | 2024 |
| Alesayi Holdings Limited | London | 2022 |
| Alesco Risk Management Services Limited | London | 2008 |
| Alessi Holdings Limited | Milton Keynes | 2025 |
| Alessi Limited | Epsom | 2005 |
| Alestone Capital Limited | Cardiff | 2016 |
| Alestra Limited | London | 2002 |
| Alethea Capital Limited | London | 2010 |
| Aletheia Holdings Five Limited | London | 2015 |
| Aletheia Holdings Ltd | Cardiff | 2025 |
| Aletheia Holdings Three Limited | London | 2015 |
| Aletheian Advisors Limited | Sutton | 2019 |
| Aletheum Partners (UK) Ltd | London | 2025 |
| Alethic Capital Ltd | London | 2025 |
| Alethinos Ltd | London | 2021 |
| Alev UK Secured Credit I Limited | London | 2011 |
| Aleva Holdings Limited | Wilmslow | 2019 |
| Alevio Group Ltd | Birmingham | 2022 |
| Alex 1 Holdings Ltd | Leicester | 2021 |
| Alex Ashworth Financial Solutions Limited | Birmingham | 2023 |
| Alex Caine Ltd | Hertford | 2012 |
| Alex Carr Holdings Ltd | Hull | 2010 |
| Alex Cope Financial Services Ltd | Ebbw Vale | 2024 |
| Alex Dawson (Holdings) Limited | London | 2021 |
| Alex DE Silva & Co Limited | London | 2015 |
| Alex Duckett Limited | Bridgend | 2020 |
| Alex Eddy Mortgage Solutions Ltd | Bedford | 2026 |
| Alex Ferguson Ltd | Bristol | 2022 |
| Alex French Holdings Ltd | Dudley | 2023 |
| Alex Hammond-Chambers & Company | Edinburgh | 1990 |
| Alex Howard Financial Planning Ltd | Ipswich | 2025 |
| Alex Howard Group Ltd | Thatcham | 2020 |
| Alex James Independent Financial Advisers Ltd | Bourne End | 2012 |
| Alex Johnson Financial Services Ltd | London | 2013 |
| Alex Lloyd Holdings Limited | Shoeburyness | 2023 |
| Alex M Grant & Company Limited | Edinburgh | 2002 |
| Alex MAY Group Limited | Scarborough | 2025 |
| Alex Munro Limited | Lanarkshire | 1984 |
| Alex Pickles Limited | Dewsbury | 2018 |
| Alex R Goldstein Securities Limited | | 1962 |
| Alex S Mair (Holdings) Limited | Glasgow | 2024 |
| Alex Smellie Financial Advice Ltd | Bathgate | 2016 |
| Alex Stewart International Inspections Ltd | Bootle | 2018 |
| Alex Whittall Holdings Ltd | Gloucester | 2021 |
| Alex Wood Holdings Limited | Keele | 2025 |
| Alex Ziff Financial Planning Ltd | London | 2016 |
| Alex.Dickson & Sons,Limited | Coleraine | 1900 |
| Alexa Capital Limited | London | 2017 |
| Alexana Investments Ltd | Wallington | 2025 |
| Alexander & Bjorck Holdings Ltd | Croydon | 2024 |
| Alexander (Scotland) & Co EOT Trustees Limited | Stirling | 2023 |
| Alexander Adams Mortgage Services Ltd | New Milton | 2017 |
| Alexander Adderson Ebbsfleet Limited | Watford | 2025 |
| Alexander and Co (Wadebridge) Limited | Wadebridge | 2021 |
| Alexander Arnold Holdings Ltd | Finchley Central | 2020 |
| Alexander Associates Umbrella Holdings Limited | Brasted | 2020 |
| Alexander Bates Campbell Europe Limited | Tunbridge Wells | 2023 |
| Alexander Bates Campbell Holdings Limited | Tunbridge Wells | 2021 |
| Alexander Bates Campbell Limited | Nutley | 2010 |
| Alexander Beard Employee Ownership Trust Limited | Ellesmere Port | 2025 |
| Alexander Beard International Benefits (UK) Ltd. | Ellesmere Port | 2018 |
| Alexander Beard Investment Management Limited | Ellesmere Port | 2001 |
| Alexander Beard Ltd. | Ellesmere Port | 2003 |
| Alexander Belle Consultants Ltd | London | 2021 |
| Alexander Bonhill Limited | London | 2004 |
| Alexander Brothers Holdings Limited | Cannock | 2024 |
| Alexander Calder Financial Holdings Limited | Worksop | 2020 |
| Alexander Cameron Limited | Redruth | 2008 |
| Alexander Capital Limited | Grantham | 2024 |
| Alexander Consulting London Limited | London | 2021 |
| Alexander Cubed Holdings Limited | Tarporley | 2021 |