| ACO Electronics Limited | Manufacturing | 1987 |
| Action Time Limited | Information & communication | 2015 |
| Active Cabling Ltd | Information & communication | 2025 |
| Active Softplay Ltd | Arts & recreation | 2020 |
| Acufense Ltd | Professional & scientific | 2026 |
| AD Group Services Ltd | Administrative & support | 2018 |
| Adam & EVE Service Station Limited | Real estate | 1997 |
| Adamson Building Solutions Limited | Construction | 2007 |
| Adastral Flying Displays Limited | Transport & logistics | 2006 |
| Adcrest Limited | Extraterritorial | 1975 |
| ADK Clinical Development Consultancy Ltd | Information & communication | 2026 |
| Adrian J Saunders Ltd | Construction | 2011 |
| Adult Holidays Limited | Extraterritorial | 2017 |
| Adws Global Limited | Manufacturing | 2008 |
| Aegle Intuitive Fitness Limited | Arts & recreation | 2020 |
| Aemd Ltd | Health & social care | 2021 |
| Aero Engines & Powerplants Ltd | Manufacturing | 2023 |
| Afhn Management Ltd | Households | 2026 |
| AFN Renovations Ltd | Construction | 2015 |
| AG & DA Properties Ltd | Real estate | 2018 |
| AG Composites Ltd | Manufacturing | 2022 |
| AG FP Limited | Professional & scientific | 2026 |
| AG42 Limited | Professional & scientific | 2014 |
| Agau Associates Ltd | Administrative & support | 2021 |
| AGI SDA UK Limited | Professional & scientific | 2025 |
| Agri Straw Ltd | Agriculture & fishing | 2021 |
| Agri-Gem Limited | Wholesale & retail | 2012 |
| Agriconsult Limited | Wholesale & retail | 1999 |
| Agriforest Logging Ltd | Agriculture & fishing | 2026 |
| Agriplant Limited | Administrative & support | 2003 |
| Agrisynex Limited | Agriculture & fishing | 2025 |
| Ahjin Ltd | Wholesale & retail | 2022 |
| Ahmed Sheikh Ltd | Hospitality | 2018 |
| AHR Solutions Limited | Professional & scientific | 2012 |
| Aiben Properties UK Ltd | Real estate | 2025 |
| Aircraft Avionics Ltd | Other services | 2021 |
| Aircraft Brokerage Ltd | Wholesale & retail | 2021 |
| Aircraft Hangarage Ltd | Transport & logistics | 2020 |
| Aircraft Maintenance Ltd | Manufacturing | 2020 |
| Aircraft Spraying Ltd | Construction | 2021 |
| Airport BUS Express Limited | Transport & logistics | 2014 |
| AIX Consultancy Limited | Professional & scientific | 2016 |
| AJM Global Consulting Ltd | Professional & scientific | 2024 |
| Akhtar Waste & Energy Developments Ltd | Water & waste | 2013 |
| Aktiv Adventures Limited | Wholesale & retail | 2013 |
| AL Stanley Limited | Financial services | 2025 |
| ALB Management Services Ltd | Professional & scientific | 2025 |
| Albemarle House Residents Association Limited | Real estate | 1981 |
| Albion Moon Ltd | Wholesale & retail | 2025 |
| Albion Road Management Company Limited | Households | 1989 |
| Alchemy Bridge Ltd | Information & communication | 2025 |
| Alchimera Investors Ltd | Professional & scientific | 2024 |
| Aldapo Limited | Administrative & support | 2023 |
| Aleks Chris Commercial Solutions Ltd | Administrative & support | 2025 |
| Aleks Chris Events Limited | Hospitality | 2017 |
| Alexander Harvey Ltd | Real estate | 2025 |
| Aliwal Industries Ltd | Mining & quarrying | 2022 |
| ALL Payroll Services Ltd | Professional & scientific | 2022 |
| Allan Microscopy Ltd | Professional & scientific | 2025 |
| Alliance (Cambridge) Property Holding and Management Company Limited | Households | 1981 |
| Allied Accountancy Limited | Professional & scientific | 2017 |
| Alloy Wheel Doctor Ltd | Wholesale & retail | 2025 |
| Alltec Limited | Extraterritorial | 2016 |
| Alltec Network Ltd. | Manufacturing | 2011 |
| Alpac Advisory Limited | Professional & scientific | 2018 |
| Alphametrics Financial Systems Limited | Information & communication | 2003 |
| Alpine Resort Nannies Ltd | Administrative & support | 2018 |
| Alta Lettings Ltd. | Real estate | 2019 |
| Altadrive Limited | Education | 2024 |
| Altaras Architecture Limited | Professional & scientific | 1997 |
| Aluminati Ltd | Financial services | 2021 |
| Aluna Coffee Limited | Hospitality | 2015 |
| Amapola Properties Limited | Real estate | 2019 |
| Amazing Builders Ltd | Construction | 2023 |
| Amazon Natural Spring Waters Limited | Wholesale & retail | 2022 |
| Amazon Spring Waters Investment Limited | Professional & scientific | 2009 |
| Amber Reclaim Ltd | Professional & scientific | 2025 |
| Amphlett Consulting Ltd | Administrative & support | 2017 |
| Ampika Limited | Professional & scientific | 2003 |
| Amplified Brands Ltd | Wholesale & retail | 2025 |
| AMY Murphy Photography Ltd | Professional & scientific | 2024 |
| ANA Cafe Limited | Hospitality | 2022 |
| Anaeventmanagement Ltd | Administrative & support | 2026 |
| Analox Holdings Limited | Financial services | 2022 |
| Analox Limited | Manufacturing | 1994 |
| Anchorpoint Claimethics Ltd | Other services | 2025 |
| Anderson Heights (Norbury) Limited | Households | 2003 |
| Anderson's Hair Care Limited | Other services | 2015 |
| Anderson's Hair Limited | Other services | 2014 |
| Andrew Hodge Contracting Limited | Construction | 2011 |
| Andrew Tanser Ltd | Arts & recreation | 2013 |
| Andybyte Limited | Professional & scientific | 1989 |
| Anglian Inspections Ltd | Administrative & support | 2018 |
| Anita Marie Ltd | Professional & scientific | 2019 |
| Anna Coen Ltd | Health & social care | 2020 |
| Annette Court Management Limited | Households | 1990 |
| ANS Technical Ltd | Construction | 2013 |
| Anstey Hall Barns Management Company Limited | Households | 2015 |
| Antique Finds Limited | Wholesale & retail | 2003 |
| Antola Ltd | Information & communication | 2004 |