| AM Nurburgring Racing Limited | Extraterritorial | 2012 |
| Amalek Limited | Financial services | 2010 |
| Aman Habesha Ltd | Wholesale & retail | 2026 |
| Amanda Ghost Limited | Information & communication | 2024 |
| Ambar Installations Ltd | Administrative & support | 2018 |
| Ambar Properties Ltd | Real estate | 2020 |
| Ambition Properties Limited | Real estate | 2018 |
| Amexin Limited | Professional & scientific | 2020 |
| AMF Commercials Ltd | Real estate | 2026 |
| Amicus Living Limited | Real estate | 2025 |
| Amis-Mcp International Limited | Professional & scientific | 2021 |
| Amlproto Limited | Manufacturing | 2016 |
| Amor Removals Ltd | Transport & logistics | 2015 |
| Amorphous Europe Limited | Information & communication | 2024 |
| Ampersand Parker Ltd | Information & communication | 2023 |
| Amplio Limited | Professional & scientific | 2018 |
| Amroth Limited | Real estate | 2021 |
| Amtec Machinery LLP | | 2025 |
| Amusement Park Spares Limited | Wholesale & retail | 1994 |
| AMY Dalton-Hardy Ltd | Information & communication | 2025 |
| AMY Hibbitt Limited | Professional & scientific | 2023 |
| AMY Shore Photography Ltd | Professional & scientific | 2018 |
| Anatis Investment Holdings Ltd | Real estate | 2022 |
| Anatomic Limited | Wholesale & retail | 2018 |
| ANC Trading Limited | Other services | 2020 |
| Anchor Point Psychotherapy Ltd | Health & social care | 2026 |
| AND Evolve Ltd | Professional & scientific | 2015 |
| Anderson and Co Asset Management Limited | Real estate | 2022 |
| Andrew Brookes Architect Limited | Other services | 2018 |
| Andrew Brookes Historic Buildings Consultant Ltd | Arts & recreation | 2026 |
| Andrew Davies (Bakeries) Limited | Wholesale & retail | 2001 |
| Andrican Limited | Professional & scientific | 2015 |
| Andromeda Holdco Limited | Financial services | 2024 |
| Andromeda Midco Limited | Financial services | 2024 |
| Anifeed Ltd | Wholesale & retail | 2014 |
| Animos Properties Limited | Real estate | 2021 |
| Anita Consult Limited | Health & social care | 2025 |
| Anna & Hubert Labs UK Limited | Information & communication | 2024 |
| Anna MAS Limited | Professional & scientific | 2014 |
| Annabel Estates Limited | Real estate | 2026 |
| Annette Cove Associates Ltd | Administrative & support | 2008 |
| Ansel Consulting Limited | Professional & scientific | 2015 |
| Anslemdestiny Ltd | Health & social care | 2018 |
| Anstee & Co Limited | Financial services | 2012 |
| Anstra Projects Limited | Information & communication | 2026 |
| Antech Diagnostics Limited | Professional & scientific | 2021 |
| Antelope Warwick Ltd | Hospitality | 2021 |
| Antimicrobial Discovery Solutions Limited | Professional & scientific | 2015 |
| Anton & Brock Limited | Wholesale & retail | 2020 |
| APA Engineering UK Limited | Professional & scientific | 2024 |
| Apeth Holdings Limited | Real estate | 2025 |
| Apex Resource Management Limited | Administrative & support | 1986 |
| Aplica Consulting Ltd | Information & communication | 2010 |
| App Intelligence Ltd | Information & communication | 2011 |
| Applegrove (Oxhill) Management Company Limited | Real estate | 2019 |
| Appletree Consulting Limited | Professional & scientific | 2005 |
| Applidd Solutions Limited | Information & communication | 2007 |
| Applied Geology Limited | Professional & scientific | 2009 |
| Applied Logic Limited | Professional & scientific | 1996 |
| Appoly Group Ltd | Information & communication | 2020 |
| Appoly Ltd | Information & communication | 2017 |
| Appoly Property Ltd | Real estate | 2024 |
| Appoly Sourcing Ltd | Wholesale & retail | 2022 |
| Apteco Limited | Information & communication | 2000 |
| Aptugo Limited | Information & communication | 2020 |
| Aqua Medical Limited | Wholesale & retail | 2023 |
| Aquarius Heat Pumps Limited | Construction | 2016 |
| Aquila Interactive Limited | Information & communication | 2023 |
| ARA Mercia Properties Limited | Real estate | 2025 |
| Araknid Limited | Professional & scientific | 2009 |
| Aranix Global Limited | Information & communication | 2026 |
| ARB (Svlp) Limited | Information & communication | 2014 |
| ARB Motors Limited | Extraterritorial | 2013 |
| Arccell Limited | Professional & scientific | 1990 |
| Archera Limited | Arts & recreation | 2002 |
| Archevia Ltd | Professional & scientific | 2025 |
| Archimedia Productions Limited | Information & communication | 2013 |
| Arctic BIT Ltd | Information & communication | 2012 |
| Arcusin Principle Hydrodynamics & Energy Co. Limited | Financial services | 2020 |
| Arden Farriers Limited | Agriculture & fishing | 2026 |
| Arden Primary Care Limited | Health & social care | 2008 |
| Arden's Coffee Ltd | Hospitality | 2021 |
| AREA9 Lyceum Ltd | Information & communication | 2023 |
| Argento Equestrian Limited | Wholesale & retail | 2020 |
| Argo Brokerage Services Limited | Transport & logistics | 2024 |
| Argo Leisure Limited | Transport & logistics | 2022 |
| Argo Nautical Limited | Transport & logistics | 1964 |
| Argos Multilingual UK Ltd | Professional & scientific | 2015 |
| Arlescote Woods Limited | Agriculture & fishing | 2016 |
| Armada Properties Limited | Real estate | 2001 |
| Armonico Consort Limited | Arts & recreation | 2003 |
| ARP Build Ltd | Other services | 2016 |
| Arriveby Limited | Information & communication | 2022 |
| Art Lounge Galleries Limited | Wholesale & retail | 2016 |
| Art Networks Design Limited | Professional & scientific | 2007 |
| Artique Galleries Limited | Wholesale & retail | 2007 |
| Artique Limited | Wholesale & retail | 2005 |
| Artisan Stoneworks Limited | Construction | 2012 |
| Arty Splats Ltd | Education | 2017 |
| Arya Sharma Properties Limited | Real estate | 2024 |