| ALC Outreach Limited | Health & social care | 2025 |
| Alcait Investments Limited | Real estate | 2015 |
| Alcester Auto Services Ltd | Wholesale & retail | 2019 |
| Alchemist Palace Ltd | Professional & scientific | 2021 |
| Alchemy Community Care Ltd | Health & social care | 2026 |
| Alchemy Entertainment Group Limited | Information & communication | 2024 |
| Alchemy Expo Digital Limited | Information & communication | 2016 |
| Alchemy of Colour Ltd | Other services | 2023 |
| Alchemy Studios Consultancy Ltd | Professional & scientific | 2017 |
| Alchemy Tuition Ltd | Education | 2020 |
| Alchemydd Eiddo Limited | Real estate | 2017 |
| Alclusio AI Limited | Information & communication | 2025 |
| Alco Team Limited | Transport & logistics | 2012 |
| Alcock Fabrications Ltd | Construction | 2019 |
| Alcredo Limited | Transport & logistics | 2020 |
| Alct Properties Ltd | Real estate | 2021 |
| Alcyone AI Ltd | Information & communication | 2026 |
| Alcyonis Maritime Limited | Extraterritorial | 2018 |
| ALD Jackom Limited | Professional & scientific | 2021 |
| ALD Ltd | Real estate | 2025 |
| Alda-Autos Ltd | Wholesale & retail | 2017 |
| Aldalarann Ltd | Information & communication | 2015 |
| Aldaniti International Network Ltd | Information & communication | 2009 |
| Aldemont Limited | Hospitality | 2015 |
| Alder Court (Luton) Limited | Households | 1984 |
| Alderhirst Limited | Health & social care | 2011 |
| Alderstead Property Management Services Limited | Households | 2004 |
| Alderwicks Consultants Limited | Professional & scientific | 2003 |
| Aldhubaibi Trading Ltd | Wholesale & retail | 2025 |
| Aldihnayn Ltd | Wholesale & retail | 2025 |
| Aldini Ltd | Manufacturing | 2025 |
| Aldrebe Constructions Limited | Construction | 2021 |
| Aldrich Capital Ltd | Professional & scientific | 2025 |
| Aldridge Contracts Ltd | Information & communication | 2018 |
| Aldworth King Ltd | Education | 2022 |
| Aleatoria Group Limited | Professional & scientific | 2016 |
| Alecto Collective Limited | Arts & recreation | 2025 |
| Aled Garfield Ltd | Administrative & support | 2012 |
| Aled Rhys Evans Ltd | Health & social care | 2014 |
| Aleed Ltd | Real estate | 2022 |
| Aleena Property Ltd | Real estate | 2024 |
| Alegre Estates Limited | Financial services | 2024 |
| Alegro Leather Limited | | 1987 |
| Aleppo Gate Ltd | Hospitality | 2018 |
| Alera Accounting & Advisory Limited | Professional & scientific | 2025 |
| Alertbreak Ltd | Administrative & support | 2020 |
| Alerte Universal Limited | Administrative & support | 2024 |
| Alesi Surgical Limited | Professional & scientific | 2007 |
| Alesia Ltd | Wholesale & retail | 2022 |
| Alesko Services Ltd | Information & communication | 2020 |
| Alespa Limited | Transport & logistics | 2019 |
| Alessia House Style UK Limited | Wholesale & retail | 2022 |
| Alessia’S Cakes Ltd | Manufacturing | 2018 |
| Alestone Capital Limited | Financial services | 2016 |
| Aletheia Holdings Ltd | Financial services | 2025 |
| Alex & Denisa's Constructions World Ltd | Construction | 2017 |
| Alex and Annie Ltd | Wholesale & retail | 2021 |
| Alex Auto Ltd | Other services | 2018 |
| Alex Betti Limited | Information & communication | 2017 |
| Alex Brown 1989 Ltd | Other services | 2020 |
| Alex Cafe (North Road) Limited | Hospitality | 2020 |
| Alex Clark Studio Limited | Professional & scientific | 2006 |
| Alex Concept Limited | Construction | 2015 |
| Alex Courier Logistics Limited | Transport & logistics | 2014 |
| Alex Dale Photography Ltd | Professional & scientific | 2023 |
| Alex Graphics Designer Limited | Professional & scientific | 2024 |
| Alex Green Groceries Ltd | Wholesale & retail | 2026 |
| Alex James Consulting Ltd | Administrative & support | 2012 |
| Alex James Estates Ltd | Real estate | 2024 |
| Alex James Flowers Limited | Wholesale & retail | 2018 |
| Alex Mathers Services Limited | Administrative & support | 2017 |
| Alex Serban Transport Limited | Transport & logistics | 2019 |
| Alex Traders Ltd | Wholesale & retail | 2025 |
| Alex.W Limited | Wholesale & retail | 2025 |
| Alexander & Alexander Ltd | Wholesale & retail | 2026 |
| Alexander & Parsons Limited | Wholesale & retail | 1973 |
| Alexander Bullock Furniture Ltd | Manufacturing | 2003 |
| Alexander Construction Manchester Ltd | Construction | 2019 |
| Alexander Crown Limited | Construction | 2017 |
| Alexander D Phillips Ltd | Agriculture & fishing | 2026 |
| Alexander Gibbons Audio Ltd | Arts & recreation | 2025 |
| Alexander Gibson Ltd | Wholesale & retail | 2015 |
| Alexander Greens Retail Ltd | Wholesale & retail | 2016 |
| Alexander Group Europe Ltd | Financial services | 2014 |
| Alexander Hamilton Limited | Information & communication | 2014 |
| Alexander Hawthorn Management Limited | Households | 2014 |
| Alexander Miles Ltd | Professional & scientific | 2017 |
| Alexander Miller Events Management Ltd | Hospitality | 2020 |
| Alexander Miller Exports Ltd | Manufacturing | 2020 |
| Alexander Paul Ltd | Administrative & support | 2012 |
| Alexander Property Holdings Ltd | Real estate | 2020 |
| Alexander Steinbeck (PR) Limited | Professional & scientific | 1997 |
| Alexander Steinbeck Limited | Extraterritorial | 1995 |
| Alexander Timber Trading Ltd | Wholesale & retail | 2020 |
| Alexanders Financial Advisory Ltd | Financial services | 2024 |
| Alexandra Tech LAB Ltd | Information & communication | 2025 |
| Alexandra Williams Group Limited | Construction | 2019 |
| Alexandre Services LLP | | 2018 |
| Alexgogea Ltd | Other services | 2019 |
| Alexis Barrell Ltd | Administrative & support | 2014 |