| AD Roofs Limited | Construction | 2013 |
| Adam Margetts Limited | Professional & scientific | 2003 |
| Adamant Advisory Limited | Professional & scientific | 2025 |
| Adapthal Partners Ltd | Professional & scientific | 2026 |
| Adaptive Virtual Ltd | Administrative & support | 2024 |
| ADB Interiors Ltd | Construction | 2025 |
| Addington Management Limited | Households | 2009 |
| Adele Kelly Boutique Ltd | Wholesale & retail | 2017 |
| Adiutare International Ltd | Professional & scientific | 2018 |
| ADJ Flooring Limited | Administrative & support | 2010 |
| Administrative Ltd | Administrative & support | 2023 |
| Advanced Roofing Solutions Ltd | Construction | 2006 |
| Advantage Consultancy Ltd | Professional & scientific | 2020 |
| Advantage Corporate Services Ltd | Administrative & support | 2011 |
| Advision (Services) Ltd | Administrative & support | 2013 |
| Advision Security Ltd | Administrative & support | 2004 |
| Advisory Group Partnership LLP | | 2023 |
| Advista Solutions Ltd | Professional & scientific | 2024 |
| Aegis Leadership Limited | Professional & scientific | 2024 |
| Aesalon Ltd | Administrative & support | 2010 |
| Afeeah Ltd | Professional & scientific | 2022 |
| AFH Homes Ltd | Construction | 2021 |
| AG Glass Windows & Doors Ltd | Construction | 2014 |
| AG96 Capital Ltd | Professional & scientific | 2025 |
| Agarmedical Ltd | Professional & scientific | 2020 |
| Aggrow Ltd. | Wholesale & retail | 2002 |
| Aglish Construction Limited | Construction | 2009 |
| Agnostic Systems Ltd | Professional & scientific | 2025 |
| Agropy UK Limited | Wholesale & retail | 2015 |
| AI REC Ltd | Professional & scientific | 2023 |
| Aimex Ltd | Administrative & support | 2012 |
| Aimfitwestlondon Limited | Arts & recreation | 2022 |
| Airav Consultancy Limited | Professional & scientific | 2018 |
| Airflo - Vents Limited | Administrative & support | 2010 |
| Airvaro Ltd | Professional & scientific | 2023 |
| Aizontech Ltd | Information & communication | 2024 |
| AJN Heating Limited | Construction | 2017 |
| AJP Healthcare Ltd | Health & social care | 2022 |
| AJS Construction Consultancy Ltd | Professional & scientific | 2024 |
| AJS Student Digs Limited | Real estate | 2024 |
| AK Plumbing Ltd | Construction | 2018 |
| Akaka Ltd | Professional & scientific | 2024 |
| AKD Capital Properties Ltd | Real estate | 2026 |
| Akshar Consultants Ltd | Professional & scientific | 2012 |
| Akshar M.A.K Properties Ltd | Real estate | 2026 |
| Alberts Mechanical Ltd | Construction | 2025 |
| Aldergrove & Antrim FM Limited | Information & communication | 2007 |
| Aldridge 4 Hire Limited | Transport & logistics | 2019 |
| Alex Flooring Ltd | Construction | 2023 |
| Alex Marton Fine Wines LLP | | 2014 |
| Alexander & Barclay Ltd | Construction | 2019 |
| Alexander James Homes Limited | Real estate | 1991 |
| Alexander James Investments Limited | Real estate | 2013 |
| Alexander James Lettings Limited | Real estate | 2012 |
| Alfiha Ltd | Hospitality | 2024 |
| Align Your Smile Ltd | Health & social care | 2020 |
| Aligned Industries Ltd | Professional & scientific | 2025 |
| ALL About Tax Limited | Information & communication | 2023 |
| Allday & Miller Ltd | Real estate | 2020 |
| Alliance Building Services Ltd | Construction | 2005 |
| Allinghams Creative and Media Ltd | Arts & recreation | 2014 |
| Allington Collaborative Problem Solving Limited | Other services | 2020 |
| Almani Group Ltd | Wholesale & retail | 2025 |
| Alois Technologies Limited | Administrative & support | 2017 |
| Alonso Executive Solutions Limited | Other services | 2025 |
| Alot UK Ltd | Real estate | 2025 |
| Alpa Global Ventures Ltd | Wholesale & retail | 2023 |
| Alpa Partners Ltd | Real estate | 2014 |
| Alpaca Alliance Consulting Ltd | Professional & scientific | 2021 |
| Alpha Arbor Ltd | Agriculture & fishing | 2015 |
| Alpha Business Resource EU Ltd | Construction | 2011 |
| Alpha Clinical Solutions Limited | Administrative & support | 2010 |
| Alpha Controls Limited | Professional & scientific | 1999 |
| Alpha Property Developers Ltd | Real estate | 2015 |
| ALT Finance Ltd | Financial services | 2013 |
| Alternative Motorcycle Training Ltd | Education | 2023 |
| Altoarch Limited | Professional & scientific | 1989 |
| Altovolo Ltd | Manufacturing | 2026 |
| Alutech Systems Limited | Extraterritorial | 2022 |
| Always Organised Ltd | Information & communication | 2015 |
| AM Enterprises Ltd | Other services | 2026 |
| Amadido Limited | Information & communication | 2019 |
| Amahi Properties Limited | Real estate | 2022 |
| Aman Kaur Project Support Limited | Professional & scientific | 2026 |
| Amanda Jane Burn Ltd | Health & social care | 2018 |
| Amar Samani Ltd | Real estate | 2020 |
| Amber Corporate Advisory Limited | Professional & scientific | 2024 |
| Amber Leigh Properties Ltd | Real estate | 2019 |
| Amber Leigh UK Ltd | Information & communication | 2007 |
| Amberley House (Management) Ltd | Households | 2005 |
| Ambitious Productions Ltd | Information & communication | 2016 |
| Ambrose Smith Limited | Construction | 2011 |
| Ambwani Consulting Ltd | Professional & scientific | 2018 |
| AMC Mary Caine Limited | Other services | 2026 |
| Amersham Festival of Music Limited | Arts & recreation | 2025 |
| AMH Collective Ltd | Administrative & support | 2026 |
| Amnos Ministries | Education | 2011 |
| AMORE1 Limited | Hospitality | 2025 |
| Amour Capital Ltd | Financial services | 2026 |
| Amplity Acquisition Ltd | Administrative & support | 2018 |