| ALL Propcom Limited | Real estate | 2020 |
| ALL Propres Limited | Real estate | 2020 |
| ALL Right Properties Limited | Real estate | 2021 |
| ALL Round 360 Group Ltd | Professional & scientific | 2020 |
| ALL Saints Gardens Management Company Limited | Households | 2006 |
| ALL Scaffold Limited | Construction | 2010 |
| ALL Seasons Care Services Limited | Health & social care | 2015 |
| ALL Secure Security Limited | Administrative & support | 2009 |
| ALL Things Revenue People Growth Ltd | Administrative & support | 2026 |
| ALL Three Corners Ltd | Professional & scientific | 2019 |
| ALL Time Motors Limited | Wholesale & retail | 2025 |
| ALL Time Roofing Limited | Construction | 2024 |
| ALL Trades Contracting Limited | Professional & scientific | 2005 |
| All-Tax-Solutions Limited | Professional & scientific | 2017 |
| All.Space Networks Limited | Administrative & support | 2013 |
| Allamby Holdings Ltd | Real estate | 2025 |
| Allaround Landscaping Ltd | Administrative & support | 2019 |
| Allaround UK Ltd | Construction | 2016 |
| Alldacc Group Ltd | Financial services | 2024 |
| Allday Maintenance Service Ltd | Construction | 2026 |
| Allder Glass Limited | Construction | 1997 |
| Allder Group Limited | Financial services | 2018 |
| Allder Locks Limited | Professional & scientific | 2005 |
| Allen Construction Solutions Ltd | Construction | 2015 |
| Allen's Tailored Dining Ltd | Hospitality | 2022 |
| Allergotech Limited | Information & communication | 2013 |
| Allerton Memorial Holdings Limited | Other services | 2024 |
| Allerton Memorial Services Limited | Other services | 2007 |
| Alliance CFM Group Limited | Financial services | 2024 |
| Alliance CFM Limited | Construction | 2020 |
| Alliance for Cohesion and Racial Equality Ltd | Information & communication | 2012 |
| Alliance Heating Group Ltd | Financial services | 2023 |
| Alliance Property Facilities Maintenance Ltd | Construction | 2024 |
| Allied Intergrated Care Solutions Limited | Administrative & support | 2016 |
| Allied Intergrated Services Limited | Health & social care | 2012 |
| Allin & Wade Investments Ltd | Real estate | 2007 |
| Allingham Homes Ltd | Construction | 2010 |
| Allington Management Company Limited | Households | 2009 |
| Alliora Ltd | Information & communication | 2025 |
| Allium Technologies Limited | Information & communication | 2024 |
| Allivo Limited | Wholesale & retail | 2025 |
| Allopa Limited | Information & communication | 2015 |
| Allosaurus Ltd | Financial services | 2024 |
| Allotment Live Ltd | Arts & recreation | 2024 |
| Allotment Productions Ltd | Wholesale & retail | 2016 |
| Allotment Property Investments Limited | Real estate | 2026 |
| Allpoints Fibre Networks Limited | Information & communication | 1997 |
| Allpresent Limited | Wholesale & retail | 1997 |
| Allpro Support Services UK Limited | Administrative & support | 2019 |
| Allsopp Studio Limited | Professional & scientific | 2022 |
| Allsorts Products Ltd | Wholesale & retail | 2019 |
| Allstyles Fascia, Soffits & Guttering Ltd | Construction | 2025 |
| Alltip Limited | Wholesale & retail | 2016 |
| Allwood Sash Limited | Construction | 2013 |
| ALM Electrical Services Limited | Construction | 2021 |
| Almabo Ltd | Construction | 2019 |
| Almasty LLP | | 2013 |
| Almec Fencing Limited | Construction | 1991 |
| Almido Ltd | Health & social care | 2022 |
| Almond Tree Consulting Limited | Professional & scientific | 2007 |
| Almond Tree Strategic Consulting Limited | Professional & scientific | 2020 |
| Alnaji Limited | Wholesale & retail | 2014 |
| Alobraziluk Ltd | Wholesale & retail | 2023 |
| Aloshebi & Associates Ltd | Professional & scientific | 2023 |
| Alpa Limited | Hospitality | 2018 |
| Alparil Ltd | Manufacturing | 2026 |
| Alparslan Ltd | Hospitality | 2022 |
| ALPARSLAN26 Limited | Households | 2026 |
| Alpestris Ltd | Professional & scientific | 2006 |
| Alpextus Limited | Professional & scientific | 2025 |
| Alpha & Omega Associate Limited | Transport & logistics | 2025 |
| Alpha Aerial Services Limited | Information & communication | 2004 |
| Alpha Anodising UK Limited | Manufacturing | 2008 |
| Alpha Cars Wokingham Ltd. | Transport & logistics | 2024 |
| Alpha Electrical (Reading) Limited | Wholesale & retail | 1987 |
| Alpha Heat Mechanical Ltd | Construction | 2019 |
| Alpha House (Reading) Limited | Households | 1960 |
| Alpha Lima Trading Ltd | Wholesale & retail | 2020 |
| Alpha OWL Ltd | Real estate | 2019 |
| Alpha Power Electrical Solutions Ltd | Construction | 2026 |
| Alpha Property Insight Ltd | Information & communication | 2018 |
| Alpha Property Ventures Limited | Construction | 2024 |
| Alpha Reach Ltd | Information & communication | 2024 |
| Alpha Windows (Southern) Ltd | Construction | 2013 |
| Alpha Zulu Trading Ltd | Wholesale & retail | 2024 |
| ALPHA7777 Limited | Real estate | 2016 |
| Alphabright Solutions Ltd | Information & communication | 2024 |
| Alphacom Systems Ltd | Professional & scientific | 2024 |
| Alphamax Developments Ltd | Real estate | 2022 |
| Alphamax One Limited | Real estate | 2020 |
| Alpine Audio-Visual Limited | Information & communication | 2021 |
| Alpine Systems UK Ltd | Wholesale & retail | 2000 |
| Alpineview Limited | Administrative & support | 2006 |
| Alpinista Limited | Financial services | 2022 |
| Alpoz Limited | Professional & scientific | 2003 |
| Alps Property Limited | Real estate | 2019 |
| Alrafay Limited | Wholesale & retail | 2022 |
| Alrahma Company Limited | Wholesale & retail | 2002 |
| Alsafadi Limited | Information & communication | 2015 |
| Also Cloud UK Limited | Wholesale & retail | 2022 |