| About Mental Health Ltd | Professional & scientific | 2021 |
| Absolute AG Holdings Limited | Financial services | 2024 |
| Absolute Air & GAS Limited | Manufacturing | 2011 |
| Absolute Automation Group Limited | Manufacturing | 2015 |
| Absolute Automation Limited | Manufacturing | 2010 |
| Absolute Contract Services Limited | Professional & scientific | 1993 |
| Absolute Measurement Limited | Manufacturing | 2015 |
| Absolute Robotics Limited | Professional & scientific | 2018 |
| Absolutely Fine Productions Limited | Arts & recreation | 2022 |
| Abstrakt Holdings Limited | Financial services | 2023 |
| Abundantia Productions Limited | Arts & recreation | 2023 |
| ABW Randall Limited | Real estate | 2016 |
| AC Medical Ltd | Health & social care | 2019 |
| Ac/Kc Hvac Ltd | Construction | 2025 |
| ACA M Sports Limited | Arts & recreation | 2018 |
| Academykicks Ltd | Arts & recreation | 2019 |
| Accattone Limited | Information & communication | 2016 |
| Access Alliance Ltd | Administrative & support | 2010 |
| Access Barriers UK Ltd | Manufacturing | 2018 |
| Account One Limited | Information & communication | 2020 |
| Accs Films Limited | Information & communication | 2022 |
| Ace ATV Limited | Administrative & support | 2008 |
| Aceofheartsuk Ltd | Wholesale & retail | 2025 |
| Acer Clinic Tamworth Limited | Health & social care | 2020 |
| ACF Design and Renovate Limited | Real estate | 2026 |
| Achilles Products Limited | Professional & scientific | 2006 |
| ACI Contech Ltd | Professional & scientific | 2017 |
| ACJ Furniture Ltd | Manufacturing | 2020 |
| ACJ Retaining Solutions Ltd | Construction | 2025 |
| Acms Waste Limited | Water & waste | 2017 |
| Acorn Venture Limited | Administrative & support | 1988 |
| Acqsys Supply Chain Holdings Limited | Professional & scientific | 2015 |
| Acqsys Supply Chain Solutions Limited | Professional & scientific | 2005 |
| Acre 1223 Limited | Administrative & support | 2020 |
| Actas UK Ltd | Professional & scientific | 2021 |
| Active Care Solutions Limited | Health & social care | 2012 |
| Activelife Perks Ltd | Professional & scientific | 2024 |
| Activewear Group Ltd | Wholesale & retail | 2018 |
| AD Kitchens & Bathrooms Ltd | Construction | 2020 |
| Ad-Vise (UK) Limited | Professional & scientific | 2006 |
| Adam Billig Property Ltd | Administrative & support | 2013 |
| Adapt Flooring Ltd | Construction | 2020 |
| ADB Accounts Midlands Limited | Professional & scientific | 2018 |
| ADB Management Services Limited | Public administration | 2018 |
| ADC Property Lettings Ltd | Real estate | 2015 |
| Addcas Limited | Financial services | 2023 |
| Adderley Hill Properties Limited | Real estate | 2017 |
| Addica Limited | Manufacturing | 1969 |
| Addison Structural Limited | Construction | 2003 |
| Addmore London Ltd | Professional & scientific | 2017 |
| Addresszone Ltd | Other services | 2022 |
| Addzen Ltd | Wholesale & retail | 2024 |
| Adika Build Ltd | Construction | 2025 |
| Adil Store Limited | Wholesale & retail | 2024 |
| Aditya Sood's UK Company Limited | Information & communication | 2024 |
| Adkins Electrical Services Ltd | Construction | 2022 |
| Adopters for Adoption Limited | Health & social care | 2013 |
| Adrian Digital Ltd | Wholesale & retail | 2025 |
| Adroit Estate Management Limited | Real estate | 2022 |
| Advance Cooler Technology Limited | Extraterritorial | 2020 |
| Advanced Maintenance Support LLP | | 2022 |
| Advanced Pools Service Limited | Construction | 2001 |
| Advanced Precision CNC Limited | Manufacturing | 2013 |
| Advanced Precision Holdings Ltd | Financial services | 2019 |
| Advent Catering Equipment Limited | Hospitality | 2015 |
| ADZ Edit Limited | Information & communication | 2022 |
| AE3 Media Ltd. | Professional & scientific | 2014 |
| Aegis Advanced Metals Limited | Wholesale & retail | 2014 |
| Aegisvest Limited | Wholesale & retail | 2026 |
| Aeroshield-Direct Ltd | Wholesale & retail | 2025 |
| Aerterra Consulting LLP | | 2019 |
| Aesthetics Engineering Limited | Manufacturing | 2013 |
| Aethelgard Limited | Wholesale & retail | 2026 |
| Affiliated Home Resolutions Ltd | Construction | 2025 |
| Affordable Kitchens Limited | Extraterritorial | 1999 |
| AFH Acquisitions Limited | Financial services | 2009 |
| AFH Corporate Services Limited | Administrative & support | 2014 |
| AFH Financial Group Limited | Financial services | 2011 |
| AFH Group Limited | Financial services | 1990 |
| AFH Independent Financial Services Limited | Financial services | 2000 |
| AFH Legal Limited | Professional & scientific | 2011 |
| AFY Entertainment Limited | Arts & recreation | 2011 |
| AFY Music Limited | Information & communication | 2024 |
| AG Bespoke Brickwork Ltd | Construction | 2021 |
| AG Education Consultancy Limited | Education | 2021 |
| AG Sports Therapy, Massage & Rehab Ltd | Other services | 2023 |
| Agency Properties Limited | Real estate | 1999 |
| Agile Advantage Limited | Information & communication | 2015 |
| Agri-Build Services Limited | Construction | 2008 |
| Agricultural and Farming Jobs Limited | Professional & scientific | 2013 |
| Agrilife Limited | Real estate | 2013 |
| Agriline Products Holdings Limited | Financial services | 2012 |
| Agzif Ltd | Wholesale & retail | 2021 |
| AH Plant & Sons Ltd | Construction | 2026 |
| AI Logic Digital Limited | Information & communication | 2025 |
| Aide VA Ltd | Administrative & support | 2018 |
| Aifsl Employees Trustees Limited | Professional & scientific | 2017 |
| Air 2 Root Turfcare Limited | Other services | 2019 |
| Air Aesthetics Birmingham Ltd | Health & social care | 2016 |
| Air Aesthetics Clinic ST Albans Ltd | Other services | 2022 |