| Alfred Middlehurst Engineering Services Limited | Administrative & support | 2016 |
| Algae Research Ltd | Professional & scientific | 2020 |
| ALI Clinical Systems Solutions Limited | Professional & scientific | 2022 |
| Alianza UK Technologies Limited | Financial services | 2024 |
| Alice Wooldridge Stevens Limited | Information & communication | 2014 |
| Align Community Care Limited | Administrative & support | 2021 |
| Align Corporation Limited | Professional & scientific | 2024 |
| Alignme Limited | Professional & scientific | 2014 |
| Alike Labs Ltd | Wholesale & retail | 2025 |
| Alinea 2025 Limited | Arts & recreation | 2025 |
| Alison Carey VAT Limited | Professional & scientific | 2021 |
| Alison Wheeler - People Matters Limited | Administrative & support | 2018 |
| Alisonpj Ltd | Professional & scientific | 2019 |
| Alitza Care Ltd | Health & social care | 2016 |
| Aljazari Centre Limited | Education | 2017 |
| Alkaam Ltd | Real estate | 2025 |
| Alkaloid UK Limited | Wholesale & retail | 2021 |
| Alkhaddar Ltd | Health & social care | 2012 |
| Alkhaddar Properties Ltd | Households | 2017 |
| Alkrington Pharm Ltd | Wholesale & retail | 2023 |
| ALL About Languages Ltd | Education | 2015 |
| ALL Car Group Limited | Extraterritorial | 2015 |
| ALL Car Leasing Limited | Administrative & support | 2011 |
| ALL Car Logistics Ltd | Transport & logistics | 2018 |
| ALL Computers UK Limited | Wholesale & retail | 2003 |
| ALL Construction Group Limited | Real estate | 2025 |
| ALL Fibre Networks Ltd | Professional & scientific | 2022 |
| ALL Glass and Glazing (NW) Limited | Construction | 2018 |
| ALL Guard Roofing Ltd | Construction | 2025 |
| ALL in Projects Ltd | Administrative & support | 2026 |
| ALL Saints Students Ltd | Households | 2013 |
| ALL Sports News Ltd | Arts & recreation | 2019 |
| ALL Stars 7012 Ltd | Wholesale & retail | 2023 |
| ALL Van Leasing Ltd | Administrative & support | 2021 |
| ALL Year Getaways Ltd | Administrative & support | 2024 |
| Allan Barr Project Services Limited | Professional & scientific | 2021 |
| Allan Investment Strategies Ltd | Financial services | 2025 |
| Allan Residential Capital Ltd | Real estate | 2025 |
| Allardyce Property Group Limited | Real estate | 2024 |
| Allcode (UK) Limited | Information & communication | 2003 |
| Allcode Limited | Wholesale & retail | 2004 |
| Allegra Property Management Limited | Real estate | 2021 |
| Allen Mills Howard Limited | Professional & scientific | 2002 |
| Allenby Developments Limited | Construction | 2007 |
| Allenby Square Limited | Real estate | 2010 |
| Allens Waste Disposal Limited | Water & waste | 2003 |
| Allied International Investment Services Ltd | Financial services | 2021 |
| Allied Legal Consultants Limited | Professional & scientific | 2016 |
| Allinea Corporate Limited | Financial services | 2017 |
| Allitsen (Management Company) Limited | Households | 1994 |
| Allocate Professional Services Limited | Professional & scientific | 2025 |
| Alma 1 Consulting Limited | Professional & scientific | 2014 |
| Alma Mater Resourcing Limited | Administrative & support | 2009 |
| Alma on Demand Limited | Professional & scientific | 2014 |
| Almaher Construction Ltd | Construction | 2020 |
| Almerie Medical Services Ltd | Health & social care | 2022 |
| Almus Group Limited | Real estate | 2024 |
| Almus Limited | Professional & scientific | 1987 |
| Alnwick House Limited | Households | 2007 |
| Alogent UK Limited | Information & communication | 2016 |
| Alpaca Consultancy Limited | Professional & scientific | 2018 |
| Alpaca Realty Limited | Real estate | 2020 |
| Alpc (Guarantee) Limited | Other services | 2019 |
| Alpega TMS UK Ltd | Information & communication | 2025 |
| Alpha Experience Design Limited | Professional & scientific | 2023 |
| Alpha Machines Limited | Manufacturing | 2025 |
| Alpha ORO Limited | Professional & scientific | 2017 |
| Alpha PCB Ltd | Manufacturing | 2026 |
| Alpha Teknik Limited | Administrative & support | 2015 |
| ALPHA2OMEGA Contract Limited | Professional & scientific | 2024 |
| Alpharmaxim Limited | Professional & scientific | 2001 |
| Alphatech Consultants Limited | Information & communication | 2019 |
| Alpine Eagle Defence Ltd. | Professional & scientific | 2025 |
| Alpine Facilities Services Limited | Administrative & support | 2014 |
| Alpine Leisure Property Club Limited | Hospitality | 1999 |
| Alpine Mart Ltd | Wholesale & retail | 2025 |
| Alpine Properties (2008) Ltd | Real estate | 2008 |
| Alpinex Ltd | Other services | 2018 |
| Alpini Capital Limited | Financial services | 2021 |
| Alps Global Limited | Wholesale & retail | 2020 |
| Alrik Properties Ltd | Real estate | 2024 |
| Alrtincham Renovations Ltd | Construction | 2024 |
| ALS28 Limited | Other services | 2023 |
| Alsari Properties Management Limited | Real estate | 2023 |
| Alshanti Ltd | Health & social care | 2020 |
| ALT Legal IP Limited | Financial services | 2026 |
| ALT Space Limited | Administrative & support | 2014 |
| Alt-Technologies Limited | Information & communication | 2019 |
| Altayar Properties Ltd | Real estate | 2022 |
| Altburgh Ltd | Real estate | 2017 |
| Altcom 222 Limited | Extraterritorial | 1999 |
| Altea Property Development Limited | Other services | 2007 |
| Altechnology Limited | Information & communication | 2014 |
| Altenbrook Management Company Limited | Households | 1999 |
| Alterity Developments Limited | Construction | 1987 |
| Alterity Investments Limited | Real estate | 1987 |
| Altglen Management Company Limited | Households | 1980 |
| Alti Land Ltd | Real estate | 2010 |
| Alti Management Ltd | Real estate | 2021 |
| Altibury Ltd | Professional & scientific | 2019 |