| Access and Inclusion Ltd | Professional & scientific | 2022 |
| Access Flooring Supplies Ltd. | Construction | 1991 |
| Accomedia Services Limited | Information & communication | 2016 |
| ACCOUNTABLE4U Ltd | Professional & scientific | 2012 |
| Accoutle Properties Limited | Real estate | 2015 |
| ACD Electrical Ltd | Construction | 2021 |
| ACD Properties & Developments Ltd | Real estate | 2023 |
| Ace Animal Equine Education & Training Limited | Education | 2008 |
| Ace Auto Services Ltd | Wholesale & retail | 2000 |
| Ace Contract Flooring Limited | Construction | 2024 |
| Ace Damp & Timber Specialists Limited | Water & waste | 2009 |
| Ace Developments (Chesterfield) Limited | Construction | 2011 |
| Ace Groundworks Ltd | Construction | 2025 |
| Ace of Diamonds Software Consultancy Limited | Professional & scientific | 2015 |
| Ace Portfolios Limited | Information & communication | 2026 |
| Ace Sporting Embroidery Limited | Wholesale & retail | 2015 |
| Aceficone | Financial services | 2019 |
| Ackroyd House Limited | Health & social care | 1993 |
| ACL Environmental Services Limited | Water & waste | 2011 |
| Aclass Healthcare Ltd | Health & social care | 2025 |
| ACO Construction Ltd | Construction | 2007 |
| Acorn Building & Roofing Company Limited | Construction | 2002 |
| Acorn Driveways & Fencing Ltd | Administrative & support | 2016 |
| Acorn Jewellers of Bakewell Limited | Wholesale & retail | 2017 |
| Acorn Service Solutions Ltd | Professional & scientific | 2018 |
| Acoustic Design Technology Limited | Professional & scientific | 2002 |
| Acrl Investments Limited | Real estate | 2018 |
| Acrl Investments XV Limited | Real estate | 2018 |
| Acropolis Catering Limited | Hospitality | 2021 |
| ACS Enterprise Ltd | Hospitality | 2023 |
| ACT Systems Limited | Information & communication | 2013 |
| Action for Care Limited | Health & social care | 2008 |
| Action Glass (U.K.) Limited | Manufacturing | 2005 |
| Active Advisory Limited | Administrative & support | 2022 |
| Active Partners Trust | Education | 2017 |
| AD & Co PVT Ltd | Wholesale & retail | 2026 |
| Adamas Jewellers (2010) Limited | Wholesale & retail | 2010 |
| Adameng Limited | Manufacturing | 2003 |
| Adamo Property Limited | Real estate | 2015 |
| Adams Developments Ltd | Real estate | 2012 |
| Adapt Drainage Services Ltd | Water & waste | 2024 |
| Adapt Renewables Ltd | Construction | 2025 |
| ADC Properties Limited | Administrative & support | 2005 |
| ADC Trade Limited | Wholesale & retail | 2021 |
| ADC Ventures Limited | Manufacturing | 2010 |
| Adcor Property Ltd | Real estate | 2017 |
| Addaamo Commercial Spaces Limited | Real estate | 2023 |
| Addaamo Residential Spaces Limited | Real estate | 2023 |
| Added Value Solutions Limited | Other services | 2014 |
| Addiction Hub Limited | Administrative & support | 2025 |
| Addison Electrical Services Ltd | Construction | 2019 |
| Addit Business and Accountancy Consultancy Limited | Professional & scientific | 2021 |
| Addooco Fleet Services Limited | Information & communication | 2026 |
| Addooco IT Limited | Information & communication | 2008 |
| Addooco Technology Group Limited | Financial services | 2026 |
| Adelphi Bramah Limited | Financial services | 2013 |
| Adelphi Music Factory Limited | Arts & recreation | 2018 |
| Ademcity UK Limited | Wholesale & retail | 2026 |
| Aden House Limited | Health & social care | 1986 |
| Adessa Trading Limited | Wholesale & retail | 2019 |
| Adgiftdiscounts Limited | Wholesale & retail | 2004 |
| ADH Risk Ltd | Professional & scientific | 2016 |
| Adhillon Solutions Ltd | Information & communication | 2019 |
| ADI Developments Ltd | Extraterritorial | 2010 |
| ADK9 Trained Dogs Ltd | Other services | 2021 |
| Adlington Electrical Limited | Construction | 2015 |
| Admani Management Limited | Professional & scientific | 2012 |
| Admiral Crookes Limited | Hospitality | 2023 |
| Adrian London Landscaping Ltd | Administrative & support | 2025 |
| Adsumnet Ltd | Information & communication | 2018 |
| Advanced Home Improvements UK Ltd | Construction | 2020 |
| Advanced Machine Maintenance Limited | Professional & scientific | 2016 |
| Advanced Service Care Ltd | Construction | 2000 |
| Advanced Service Plan Limited | Construction | 2021 |
| Advertel Ltd | Professional & scientific | 2005 |
| ADW Fire & Security Ltd | Administrative & support | 2018 |
| ADY Building Ltd | Construction | 2013 |
| ADY Mathews Limited | Hospitality | 2002 |
| Ae-Sthetics MAY Ltd | Other services | 2024 |
| Aequatech UK Limited | Administrative & support | 2017 |
| Aerial Inspection & Mapping Surveys Ltd. | Mining & quarrying | 2015 |
| Aerial Planning Limited | Professional & scientific | 2021 |
| Aero Gears Limited | Extraterritorial | 2012 |
| Aerocal Limited | Professional & scientific | 2011 |
| Aerospace Gears Limited | Extraterritorial | 2012 |
| Aesthetic Security Ltd | Information & communication | 2025 |
| Aesthitikos Ltd | Health & social care | 2021 |
| AFA Solutions Limited | Extraterritorial | 2011 |
| Affordable Intelligence Limited | Administrative & support | 2020 |
| Affordable Mortgages Limited | Extraterritorial | 2024 |
| Affordable Mortgages.Co.Uk Limited | Extraterritorial | 2023 |
| Aflorist Ltd | Wholesale & retail | 2024 |
| Aflowan Ltd | Manufacturing | 2017 |
| African Spirits Ltd | Wholesale & retail | 2024 |
| AFS Limited | Financial services | 2001 |
| AG Building Ltd | Construction | 2021 |
| AGA Electronics Ltd | Wholesale & retail | 2013 |
| Agathos Care Services Limited | Public administration | 2024 |
| AGE Care Bathrooms Ltd | Construction | 2018 |
| AGE Care Maintenance Ltd | Manufacturing | 2024 |