| ALL Security Matters Limited | Administrative & support | 2025 |
| ALL Sparks Technical Ltd | Manufacturing | 2015 |
| ALL Star Funding Solutions Limited | Financial services | 2017 |
| ALL Style Marquee & Events Limited | Other services | 2014 |
| ALL the Power Ltd | Professional & scientific | 2020 |
| ALL Things Equal Limited | Information & communication | 2023 |
| ALL Ways Books Ltd | Information & communication | 2026 |
| All/Within Ltd | Information & communication | 2022 |
| Allbag Services Ltd | Wholesale & retail | 2026 |
| Allclear Maintenance Ltd | Other services | 2025 |
| Allecstransport Ltd | Transport & logistics | 2026 |
| Allegro Developments Limited | Real estate | 2020 |
| Allen BJJ Limited | Arts & recreation | 2024 |
| Allen Diesels Limited | Manufacturing | 2009 |
| Allgood Property Group Ltd | Real estate | 2025 |
| Alliance Bloodstock Ltd | Agriculture & fishing | 2017 |
| Alliance Graphics Limited | Manufacturing | 1998 |
| Alliance Trading Group Ltd | Manufacturing | 2023 |
| Allied Comline Limited | Wholesale & retail | 1997 |
| Allied Maintainance Ltd | Construction | 2023 |
| Alloggi Limited | Other services | 2014 |
| Alloy Artistry Limited | Water & waste | 2025 |
| Alltech Business Solutions Ltd | Administrative & support | 2020 |
| Almar Business and Finance Ltd | Professional & scientific | 2017 |
| Almar Housing Partnership LLP | | 2011 |
| Almat Group Ltd | Households | 2024 |
| Almond Garage Doors Limited | Administrative & support | 2025 |
| Almonds Management Limited | Professional & scientific | 2018 |
| Almusly Ltd | Hospitality | 2024 |
| Aloe Bay Consulting Limited | Professional & scientific | 2008 |
| Aloha Beautiful Hair Ltd | Other services | 2019 |
| Alom Management Ltd | Real estate | 2024 |
| Alona Susloparova Beauty Limited | Other services | 2025 |
| Alpav Project Management Ltd | Construction | 2024 |
| Alpha Alpha Property Ltd | Real estate | 2025 |
| Alpha Converting Equipment Limited | Manufacturing | 2000 |
| Alpha Converting Property Limited | Real estate | 2016 |
| Alpha Crest Services Ltd | Transport & logistics | 2022 |
| Alpha Feast Ltd | Hospitality | 2026 |
| Alpha Hvac UK Ltd | Construction | 2019 |
| Alpha Lifepath Ltd | Health & social care | 2025 |
| Alpha Lifts Ltd | Manufacturing | 2023 |
| Alpha Muscle Gym Limited | Arts & recreation | 2024 |
| Alpha One Cars Limited | Transport & logistics | 2025 |
| Alpha Recycling Solutions Ltd | Professional & scientific | 2012 |
| Alpha Science Ltd | Wholesale & retail | 2026 |
| Alpha Security Industries Ltd | Administrative & support | 2015 |
| Alpha Sourcing and Marketing Ltd | Transport & logistics | 2016 |
| Alpha Sport (Bedford) Ltd | Administrative & support | 2021 |
| Alpha Training Industries Ltd | Education | 2020 |
| Alphanetz Ltd | Professional & scientific | 2015 |
| Alphateck Engineering and Services Ltd | Professional & scientific | 2025 |
| Alpine Security (UK) Limited | Construction | 2002 |
| Alptekin Limited | Wholesale & retail | 2022 |
| Alruco Group Ltd | Real estate | 2026 |
| Alsamex Products Limited | Manufacturing | 1957 |
| Alston Engineering Services Ltd | Professional & scientific | 2022 |
| Altered Carbon Heating and Cooling Ltd | Construction | 2020 |
| Alternative H R Limited | Administrative & support | 2004 |
| Alternative Medicine Incorporated Limited | Health & social care | 2013 |
| Altnaharra Hotel LLP | | 2009 |
| Alto Designs Ltd | Information & communication | 2022 |
| Altovara Consulting Limited | Professional & scientific | 2026 |
| Altradev Limited | Information & communication | 2006 |
| Alugroup Limited | Manufacturing | 2009 |
| Alure Business Services Ltd | Professional & scientific | 2025 |
| Alvera Group Ltd | Hospitality | 2026 |
| Alvest Equipment Services (UK) Limited | Administrative & support | 2020 |
| Alvin Consultants Limited | Real estate | 2013 |
| Always Together Homecare Ltd | Health & social care | 2024 |
| Alxr Services Limited | Professional & scientific | 2025 |
| AM Cars and Commercial Ltd | Transport & logistics | 2019 |
| AM1 Investing Ltd | Real estate | 2025 |
| AM14 Care Services Limited | Health & social care | 2023 |
| AM2PM Electrical Ltd. | Construction | 2014 |
| AM2PM Haulage Services Ltd | Other services | 2015 |
| AM2PM Healthcare Limited | Health & social care | 2025 |
| AM3 Ltd | Professional & scientific | 2025 |
| Amaana Care Ltd | Health & social care | 2023 |
| Amac Civils Limited | Construction | 2012 |
| Amac Support Services Ltd | Public administration | 2025 |
| Amaharji Holdings Limited | Real estate | 2025 |
| Amaharji Limited | Hospitality | 2025 |
| Amakipp Ltd | Administrative & support | 2020 |
| Amanda Jane Consultancy Ltd | Manufacturing | 2022 |
| Amanda REA Ltd | Professional & scientific | 2015 |
| Amanda Wade Limited | Professional & scientific | 2013 |
| Amani Collective Ltd | Other services | 2023 |
| Amar Nath Properties Ltd | Real estate | 2023 |
| Amar Trading Ltd | Construction | 2016 |
| Amara MK Ltd | Hospitality | 2024 |
| AMB Management & Consultancy Limited | Arts & recreation | 2018 |
| AMB Ventures Limited | Real estate | 2018 |
| Amber Masterson Neuro SLT Limited | Health & social care | 2023 |
| Amberview Ltd | Administrative & support | 2019 |
| Amberwood Advisory Services Ltd | Professional & scientific | 2025 |
| Ambivert Digital Ltd | Professional & scientific | 2024 |
| Ambulance Response Group Ltd | Health & social care | 2017 |
| Ambulance Response Services Ltd | Health & social care | 2011 |
| Amburgh Investments Limited | Other services | 2023 |