| Abbeyfield Associates Limited | Professional & scientific | 1996 |
| Abbeyfield Secretaries Limited | Professional & scientific | 1994 |
| Abbeyman Investments Limited | Real estate | 2002 |
| Abbeyman Property Services Limited | Real estate | 2008 |
| Abbotsbury Developments Ltd | Extraterritorial | 1987 |
| Abcreste Consulting Ltd. | Professional & scientific | 2013 |
| Aberdeen Assets Limited | Real estate | 2023 |
| Aberdui Ltd | Real estate | 1989 |
| Abermaed House Residents Company Limited | Households | 1999 |
| Abetta Limited | Hospitality | 2013 |
| ABH REC Limited | Administrative & support | 2006 |
| Abitativa Ltd | Construction | 2020 |
| Abjad Teach Limited | Education | 2021 |
| Abjadeeya Ltd | Manufacturing | 2021 |
| Aboat London Ltd | Administrative & support | 2016 |
| About Damn Time Studios Ltd | Information & communication | 2026 |
| Absolute CAD (UK) Limited | Construction | 2003 |
| Absolute Wimbledon Limited | Real estate | 2010 |
| Abstract Recruitment Limited | Administrative & support | 2014 |
| ABUNDANCE2020 Limited | Health & social care | 2015 |
| ABV Consulting Limited | Professional & scientific | 2014 |
| ABW Advisory Limited | Professional & scientific | 2021 |
| AC Build Services Limited | Construction | 2021 |
| Acala Online Ltd | Wholesale & retail | 2018 |
| Acaria Limited | Administrative & support | 2010 |
| Accelerated Intensity Ltd | Information & communication | 2025 |
| Accessible Travel Consultancy Ltd | Professional & scientific | 2019 |
| Accounting for Everyone Ltd | Professional & scientific | 2017 |
| Ace Create Limited | Professional & scientific | 2006 |
| Ace Stratton Ltd | Wholesale & retail | 2025 |
| Aceternity Ltd | Professional & scientific | 2024 |
| Acland Digital Content Ltd | Administrative & support | 2019 |
| Acloudcontrol Ltd | Information & communication | 2021 |
| Acorn Oak Limited | Professional & scientific | 2020 |
| Acorn Property Services (London) LLP | | 2012 |
| ACP Installation Limited | Construction | 2023 |
| Acquainted Ltd | Information & communication | 2023 |
| Acquisition 395447313 Limited | Manufacturing | 1959 |
| Acre 1224 Limited | Arts & recreation | 2020 |
| Acre Road (Kingston) Management Limited | Households | 1996 |
| ACT Coaching and Consulting Ltd | Professional & scientific | 2021 |
| Active Roofing and Guttering Ltd | Construction | 2020 |
| Activerse Productions Ltd | Arts & recreation | 2024 |
| Activo Group Limited | Administrative & support | 2023 |
| AD Idem Consulting Limited | Administrative & support | 2015 |
| AD Ingenium Limited | Professional & scientific | 2019 |
| AD OIL & GAS Advisory Limited | Administrative & support | 2019 |
| Adam Kennedy Dog Training Ltd | Households | 2024 |
| Adam Kirkaldy Limited | Professional & scientific | 2019 |
| Adamski Construction Limited | Construction | 2005 |
| Adapt OR DIE Studio Ltd | Professional & scientific | 2019 |
| Adaptive Healthcare Analytics Ltd | Information & communication | 2025 |
| Adaptive HVM UK Limited | Professional & scientific | 2018 |
| Adaptology Limited | Administrative & support | 2016 |
| Addicted to the Hustle Limited | Information & communication | 2020 |
| ADDICTED2LIFE Ltd | Wholesale & retail | 2020 |
| Addy-Kassova Audience Strategy Limited | Professional & scientific | 2012 |
| Adelabu Park Holdings Limited | Professional & scientific | 2025 |
| Adept Field Solutions Holdings Limited | Financial services | 2015 |
| Adept Field Solutions Limited | Professional & scientific | 2010 |
| Adeptbk Ltd | Information & communication | 2023 |
| Adhay Holdings Ltd | Professional & scientific | 2026 |
| Adidem Limited | Other services | 2014 |
| Adina Seven Limited | Administrative & support | 2016 |
| Adleon Ltd | Real estate | 2024 |
| Adler Family Law Solicitors LLP | | 2016 |
| Adlington Properties Limited | Real estate | 2007 |
| ADM Lindenau Acquisition Limited | Administrative & support | 2012 |
| ADM Lindenau Limited | Administrative & support | 2012 |
| Admiralty Way Owners Company Limited | Households | 2017 |
| Adnitiative Limited | Professional & scientific | 2024 |
| Adrian Fawcett Limited | Health & social care | 2010 |
| Adrian Hall Properties Limited | Real estate | 1964 |
| Adul-Thaifood Ltd | Hospitality | 2026 |
| Advance Vehicle Services Limited | Wholesale & retail | 2008 |
| Advanced Site Engineering Surveys Limited | Administrative & support | 2007 |
| Advancing 3D Design Ltd | Professional & scientific | 2021 |
| Advantage Basement & Cellar Company Limited | Construction | 2000 |
| Advantage Basements Limited | Construction | 2014 |
| Advantage Developments Limited | Construction | 2019 |
| Adwen House Publishing Limited | Arts & recreation | 2018 |
| AEC Advance Electrical Contractors Limited | Extraterritorial | 2012 |
| Aemguc Ltd | Real estate | 2024 |
| AEN Legal Ltd | Professional & scientific | 2024 |
| Aesculus Health Ltd | Health & social care | 2020 |
| Aesthetics Pro Academy Ltd | Education | 2026 |
| AF Finko Ltd | Real estate | 2025 |
| Affios Ltd | Information & communication | 2018 |
| Afrijanus Property UK 1 Limited | Real estate | 2020 |
| Afroscot Ventures Ltd | Professional & scientific | 2025 |
| Aftrnow Collective Ltd | Information & communication | 2025 |
| Afvm Maintenance Limited | Construction | 2019 |
| Agemer Limited | Professional & scientific | 2015 |
| Aggregate Investment Management Ltd | Construction | 2022 |
| Agile Data Ltd | Information & communication | 2025 |
| Agile Occupational Health Ltd | Health & social care | 2023 |
| Agilequity Ltd | Professional & scientific | 2024 |
| AGL Creative Marketing Ltd | Information & communication | 2025 |
| Agon Running Ltd | Wholesale & retail | 2024 |
| Agora Consultancy Services Ltd | Manufacturing | 2010 |