| Acumen Vehicle Logistics Limited | Transport & logistics | 2020 |
| Acurve Trend Ltd | Wholesale & retail | 2025 |
| AD Airflow System Ltd | Construction | 2025 |
| AD Insight Solutions Ltd | Professional & scientific | 2024 |
| AD Raolad Ltd | Administrative & support | 2025 |
| AD3 Healthcare Ltd | Health & social care | 2018 |
| AD3 Properties Ltd | Real estate | 2025 |
| ADA Autocare Ltd | Wholesale & retail | 2024 |
| Adact Medical Ltd | Information & communication | 2012 |
| Adailia Limited | Real estate | 2023 |
| Adal Transport Ltd | Transport & logistics | 2025 |
| Adam and Jacob Services Ltd | Information & communication | 2024 |
| Adam Linens Ltd | Manufacturing | 2013 |
| Adam Simmonds Woburn Limited | Hospitality | 2023 |
| Adam Walker Consultancy Ltd | Professional & scientific | 2022 |
| Adam Wells Flooring Limited | Construction | 2022 |
| Adamantine Pictures Limited | Administrative & support | 2007 |
| Adamas K5 Limited | Wholesale & retail | 2024 |
| Adamas Wind Limited | Professional & scientific | 2019 |
| Adams 1010 Tyre's Ltd | Wholesale & retail | 2025 |
| Adams Family Rail Ltd | Construction | 2025 |
| Adams Motors Ltd | Wholesale & retail | 2020 |
| Adams-Green Property Limited | Real estate | 2022 |
| Adamson Automotive Limited | Wholesale & retail | 2025 |
| Adam’S Healthcare Limited | Professional & scientific | 2025 |
| Adanna Healthcare Staffing Solutions Ltd | Health & social care | 2025 |
| Adansi Ventures UK Ltd | Administrative & support | 2022 |
| Adaptive Care Solutions Limited | Information & communication | 2002 |
| Adaptive IT Solutions Ltd | Information & communication | 2025 |
| Adaptive Mortgage & Protection Solutions Ltd | Financial services | 2021 |
| Adara Group Limited | Health & social care | 2016 |
| Adara Healthcare Ltd. | Health & social care | 1997 |
| Adara Holdings Ltd. | Health & social care | 2016 |
| Adario Ltd | Transport & logistics | 2017 |
| Adas Line Limited | Wholesale & retail | 2026 |
| Adcam UK Limited | Administrative & support | 1998 |
| Adcapital Property Investments Ltd | Real estate | 2024 |
| Add-Mech Ltd | Manufacturing | 2022 |
| Adders Accountants Limited | Professional & scientific | 2011 |
| Addic Digital Ltd | Wholesale & retail | 2023 |
| Addingtons Kitchens and Bathrooms Limited | Construction | 2026 |
| Addingtons Landscape Design Limited | Construction | 2017 |
| Addingyou Limited | Professional & scientific | 2024 |
| Addison Print Limited | Manufacturing | 2013 |
| Addison Road Management Limited | Households | 2021 |
| Addmore Engineering Limited | Manufacturing | 1999 |
| Addmore Precision Limited | Professional & scientific | 2020 |
| Address Barber Ltd | Other services | 2024 |
| Adedokun International Services Ltd | Wholesale & retail | 2022 |
| Adel Care Limited | Health & social care | 2017 |
| Adelahaye Ltd | Professional & scientific | 2019 |
| Adelaide Sauces Limited | Manufacturing | 2021 |
| Adelaide ST. Limited | Professional & scientific | 2025 |
| Adelux Ltd | Transport & logistics | 2025 |
| Adems Consults Limited | Information & communication | 2014 |
| Aden Health Care Ltd | Health & social care | 2022 |
| Aden Services Ltd | Information & communication | 2019 |
| Adenwood Limited | Professional & scientific | 1972 |
| Adept Build Limited | Extraterritorial | 2015 |
| Adept IS Limited | Information & communication | 2015 |
| Adept Mortgages Ltd | Financial services | 2023 |
| Adept Safety Specialist Ltd | Extraterritorial | 2022 |
| ADG Construction Ltd | Construction | 2023 |
| Adhd & ASD World Ltd | Education | 2026 |
| Adhik Ltd | Real estate | 2018 |
| ADI Trans Ltd | Transport & logistics | 2018 |
| Adien Limited | Professional & scientific | 1997 |
| Adiyogi Ltd | Wholesale & retail | 2025 |
| Adjacency Group Ltd | Professional & scientific | 2016 |
| Adlyn Ltd | Transport & logistics | 2017 |
| Admarketing Limited | Professional & scientific | 2024 |
| Admin and More Ltd | Administrative & support | 2017 |
| Administrative Services Ltd. | Professional & scientific | 2012 |
| Admiral Brickwork Ltd | Construction | 2025 |
| Admirals and Co Fish Bar Ltd | Hospitality | 2026 |
| Admiralty Global Line Limited | Hospitality | 2023 |
| Admire Healthcare Ltd | Health & social care | 2019 |
| Adonai Healthcare Ventures Ltd | Real estate | 2017 |
| Adonai Interbiz Ltd | Transport & logistics | 2024 |
| Adonis & Partners Ltd | Hospitality | 2024 |
| Adonis Health Ltd | Real estate | 2023 |
| Adora Spa Ltd | Other services | 2022 |
| Adorable Nurseries Limited | Health & social care | 2015 |
| Adorables Day Nursery Ltd | Education | 2010 |
| Adorables Homes Ltd | Real estate | 2025 |
| Ados Furniture Ltd | Wholesale & retail | 2026 |
| Ados Logistics Ltd | Transport & logistics | 2023 |
| Ados Logistics Support Limited | Transport & logistics | 2019 |
| ADP Signature Ltd | Real estate | 2025 |
| Adprestigetrans Ltd | Transport & logistics | 2025 |
| ADR Transport SVS Limited | Transport & logistics | 2022 |
| Adrian A&B Ltd | Transport & logistics | 2023 |
| Adrian Salisbury Training Limited | Professional & scientific | 2020 |
| Adrian Stanciu Ltd | Other services | 2023 |
| Adrian Transport SVS Limited | Transport & logistics | 2019 |
| Adrian Vicol Ltd | Construction | 2016 |
| Adrian&Julian Ltd | Real estate | 2023 |
| Adriandoru Ltd | Transport & logistics | 2014 |
| Adrianne Haynes-Samuel Ltd | Professional & scientific | 2025 |
| Adrigole Limited | Information & communication | 2007 |