| Aden Pharmacovigilance Services Limited | Health & social care | 2017 |
| ADI Group Ltd | Professional & scientific | 2024 |
| ADL Plumbing Ltd. | Construction | 2007 |
| Adla Technologies Ltd | Professional & scientific | 2022 |
| Admiral Offshore Limited | Manufacturing | 2018 |
| Ados/Adir Clinical Consultants Limited | Health & social care | 2026 |
| Adrara Limited | Professional & scientific | 2024 |
| Adrian Back Editorial Limited | Administrative & support | 2020 |
| Aduray Ltd | Information & communication | 2020 |
| Advance Engineering Consultancy Limited | Professional & scientific | 2018 |
| Advance Medical Consultancy Limited | Health & social care | 2023 |
| Advanced Horizons Limited | Professional & scientific | 2017 |
| Advanced Urology Limited | Health & social care | 2026 |
| Advisory Broking Ltd | Financial services | 2023 |
| Adwear Limited | Manufacturing | 2000 |
| Aeer Limited | Information & communication | 2014 |
| Aegeus Marine Limited | Manufacturing | 2010 |
| Aeolus Renewables Limited | Professional & scientific | 2025 |
| Aerial Tree Services Ltd | Agriculture & fishing | 2004 |
| Aero Elite Ltd | Wholesale & retail | 2019 |
| Aevin Ltd | Information & communication | 2023 |
| AFG (Dorset) Limited | Transport & logistics | 2010 |
| Afri-Thread Ltd | Wholesale & retail | 2019 |
| AG EM Property Ltd | Real estate | 2019 |
| AGB Consultancy Services Ltd | Administrative & support | 2015 |
| Ages IT Limited | Information & communication | 2018 |
| Aghagower Limited | Energy | 2021 |
| Agile Edge Consultancy Ltd | Information & communication | 2024 |
| Agile Incorporated Limited | Information & communication | 2024 |
| Agile Minds Work Limited | Information & communication | 2024 |
| Agile Ocean Limited | Information & communication | 2015 |
| Agile Training Plus Ltd | Other services | 2021 |
| AGR IT Limited | Information & communication | 2018 |
| AHA Consulting Solutions Limited | Information & communication | 2023 |
| AHK Services Limited | Information & communication | 2018 |
| Ahtechco Limited | Information & communication | 2018 |
| AIM High Property Limited | Real estate | 2021 |
| Aimsir Limited | Construction | 2017 |
| AIQ Consultancy Ltd | Professional & scientific | 2023 |
| Air Capture Consulting Limited | Professional & scientific | 2023 |
| Aircrates Ltd | Manufacturing | 2025 |
| Aircrew Solutions Limited | Administrative & support | 2002 |
| Airey Property Ltd | Real estate | 2017 |
| Airworld Europe Limited | Construction | 2011 |
| Aixtreme Research Limited | Information & communication | 2009 |
| AJ Digital Solutions Ltd | Information & communication | 2021 |
| AJ Reynolds Consultancy Ltd | Information & communication | 2019 |
| AJB Incorporated Ltd | Health & social care | 2013 |
| Ajet Limited | Wholesale & retail | 2006 |
| AJM Mgmt Ltd | Arts & recreation | 2019 |
| AK Investments (UK) Limited | Financial services | 2015 |
| AK Technologies Ltd. | Information & communication | 2013 |
| Akandas Ltd | Information & communication | 2019 |
| Akesios Associates Limited | Other services | 2012 |
| AKK Consultancy Limited | Information & communication | 2018 |
| Aknotts Limited | Information & communication | 2024 |
| Akpa Consulting Europe Ltd | Professional & scientific | 2017 |
| Akramms Ltd | Information & communication | 2020 |
| AL Bayan Consulting Limited | Administrative & support | 2023 |
| Alabaster Media Limited | Information & communication | 2023 |
| Alamin MJA Ltd | Wholesale & retail | 2024 |
| Alan Froud (Holdings) Limited | Real estate | 2008 |
| Alan Froud Limited | Wholesale & retail | 2008 |
| Albemarle (2003) Limited | Households | 2002 |
| Albert Villa Limited | Professional & scientific | 2025 |
| Albion Fork Lifts Limited | Other services | 2000 |
| Albuquerque Matos Realty Limited | Real estate | 2020 |
| Alchemist One Limited | Real estate | 2017 |
| Alchemy Bros Limited | Information & communication | 2017 |
| ALD Projects Ltd | Professional & scientific | 2025 |
| Alden Bethell Advisory Limited | Professional & scientific | 2016 |
| Aldgate Clinical Research Limited | Professional & scientific | 2019 |
| Aldridge Building Solutions Ltd | Construction | 2012 |
| Alethia Consulting Ltd | Information & communication | 2021 |
| Alex Bacon Consulting Services Limited | Information & communication | 2007 |
| Alex LEE Consulting Limited | Information & communication | 2018 |
| Alex LYS Osteopathy Ltd | Health & social care | 2010 |
| Alex Wood Design Services Ltd | Information & communication | 2022 |
| Alex's Window Cleaning Ltd | Administrative & support | 2017 |
| Alfacloud Ltd | Information & communication | 2017 |
| Alfamotive Limited | Wholesale & retail | 2011 |
| Aliang Lift Design Studio Ltd | Professional & scientific | 2019 |
| Alib Ltd | Professional & scientific | 2011 |
| Alice Holt Cafe Limited | Professional & scientific | 2016 |
| Align Design Ltd | Information & communication | 2022 |
| Alioe Solutions Ltd | Professional & scientific | 2016 |
| ALL Clean 24/7 UK Ltd | Administrative & support | 2018 |
| ALL of YOU Limited | Administrative & support | 2020 |
| ALL Plant Training South Limited | Education | 2000 |
| Allegiant Systems Resource Ltd | Manufacturing | 2024 |
| Allen Seymour Limited | Information & communication | 2015 |
| Allenby Solutions Limited | Information & communication | 2023 |
| Alleywool Property Ltd | Real estate | 2023 |
| Allfix Marine Limited | Wholesale & retail | 2023 |
| Allium Communications Limited | Professional & scientific | 2006 |
| Allport Holdings Ltd | Financial services | 2025 |
| Allporto Ltd | Hospitality | 2026 |
| Allsorts Software Limited | Information & communication | 2016 |
| ALM Financial Solutions Limited | Information & communication | 2011 |
| Almondburys Limited | Wholesale & retail | 2012 |