| Alphait Limited | Professional & scientific | 2004 |
| Alpine Property Search Limited | Real estate | 1989 |
| Altamira Polo UK Ltd | Agriculture & fishing | 2025 |
| Altar Construction & Building Projects Ltd | Construction | 2023 |
| Alterian Holdings Limited | Professional & scientific | 2006 |
| Alterian Technology Limited | Information & communication | 1997 |
| Alternative Minds Limited | Professional & scientific | 2004 |
| Altitude Digital IO Limited | Professional & scientific | 2026 |
| Altmore Investments Ltd | Real estate | 2020 |
| Alton Assets Limited | Real estate | 2022 |
| Altovia Consulting Services Limited | Information & communication | 2024 |
| Altra Copywrite Ltd | Administrative & support | 2017 |
| Altwood Bailey Accountants Limited | Professional & scientific | 2011 |
| Altwood Energy Advisors Limited | Professional & scientific | 2021 |
| Altwood Financial Services Limited | Professional & scientific | 2011 |
| Altwood Housing Group Limited | Construction | 2022 |
| Altwood Petroleum Limited | Mining & quarrying | 1992 |
| Alumen Consulting Ltd | Information & communication | 2006 |
| Alvi Business Activities Limited | Administrative & support | 2025 |
| Alvik Limited | Information & communication | 2011 |
| Alvise Limited | Professional & scientific | 2008 |
| Always Health Limited | Real estate | 2013 |
| Always Paid Ltd | Other services | 2024 |
| Alzheimers Dementia Support | Other services | 2011 |
| AM Co Services Ltd | Transport & logistics | 2025 |
| Amack (Builders) Limited | Construction | 2018 |
| Amada Estates Limited | Real estate | 2021 |
| Amalthaea Estates Limited | Real estate | 2023 |
| Amalthaea Properties Limited | Real estate | 2023 |
| Aman Security Ltd | Administrative & support | 2017 |
| Amanda Vine Consultancy Limited | Administrative & support | 2018 |
| Amandeep Banga Limited | Professional & scientific | 2013 |
| Amani Services Ltd | Professional & scientific | 2018 |
| Amase Limited | Professional & scientific | 2023 |
| Amavii.Co Ltd | Information & communication | 2025 |
| Amberley Solutions Ltd | Real estate | 2009 |
| AMC Consulting Services Ltd | Professional & scientific | 2025 |
| AMC Finance Ltd | Professional & scientific | 2017 |
| Amer Khan Trading Limited | Information & communication | 2015 |
| Amerden Lakes Management Company Ltd | Households | 2003 |
| Amerqureshi Ltd | Information & communication | 2017 |
| Amey Group Limited (the) | Professional & scientific | 1934 |
| Amey Roadstone International Limited | Professional & scientific | 1936 |
| Amhark Limited | Real estate | 2024 |
| Amiak Ltd | Professional & scientific | 2019 |
| Amigos Community Care Limited | Public administration | 2019 |
| Amirayasin Medicare Ltd | Health & social care | 2015 |
| Amito Ltd | Information & communication | 2012 |
| Amito Topco Ltd | Financial services | 2021 |
| Amizesh Limited | Professional & scientific | 2023 |
| AMK Travel Ltd | Transport & logistics | 2022 |
| Amloaded.Com Limited | Other services | 2016 |
| Amotech Limited | Professional & scientific | 2010 |
| AMP Consulting Limited | Professional & scientific | 2008 |
| Ample Consulting Ltd | Professional & scientific | 2024 |
| Amrit Consultancy Services Ltd | Professional & scientific | 2020 |
| Amrit Sons (UK) Limited | Extraterritorial | 2003 |
| AMS Global Limited | Administrative & support | 2006 |
| AMS Plumbing & Heating Solutions Ltd | Construction | 2026 |
| Amsaso Consulting Limited | Information & communication | 2012 |
| Amsaso Property Management Limited | Real estate | 2020 |
| AMY Bear & Family Ltd | Wholesale & retail | 2023 |
| AMY Yates Photography Ltd | Professional & scientific | 2020 |
| AN Associates Limited | Real estate | 2024 |
| AN NAM Capital Ltd | Real estate | 2022 |
| ANA Harmony Ltd | Other services | 2018 |
| Anad Ltd | Transport & logistics | 2021 |
| Anaesthetic Practitioner Ltd. | Health & social care | 2020 |
| Anaforic Ltd | Information & communication | 2021 |
| Anagha Technologies Limited | Information & communication | 2023 |
| Anah Property Services Limited | Real estate | 2021 |
| Ananda Holdings Limited | Financial services | 2015 |
| Anavrin Limited | Professional & scientific | 2004 |
| Ancreva Strategy and Brand Engineering Limited | Information & communication | 2025 |
| AND Happenings Yoga Ltd | Wholesale & retail | 2019 |
| Anderson Becker Properties Ltd | Real estate | 2016 |
| Anderson Rana International (Consultants) LLP | | 2014 |
| Andesjel Limited | Health & social care | 2026 |
| Andigital Limited | Information & communication | 2013 |
| Andilli Limited | Real estate | 2021 |
| Andra's Wellness Ltd | Arts & recreation | 2023 |
| Andrew Gordon Limited | Other services | 2011 |
| Andrew James Design Interiors Limited | Wholesale & retail | 2013 |
| Andro Trans Ltd | Transport & logistics | 2019 |
| Andy ZMH Ltd | Professional & scientific | 2025 |
| Anemone Consulting Ltd | Professional & scientific | 2022 |
| Angell Sports Limited | Manufacturing | 2012 |
| Angelo & Co Associates Ltd | Professional & scientific | 2009 |
| Angon Estates Limited | Financial services | 2018 |
| Anikom Technologies Limited | Information & communication | 2014 |
| Anima Atelier Ltd | Professional & scientific | 2025 |
| Anima Solutions Limited | Information & communication | 2010 |
| Animal Army CIC | Wholesale & retail | 2023 |
| Animo Performance Limited | Extraterritorial | 2015 |
| Anja BIO Ltd | Professional & scientific | 2023 |
| ANK Consulting Services Ltd | Information & communication | 2026 |
| ANK Global Limited | Wholesale & retail | 2023 |
| Anken Ltd | Real estate | 2019 |
| ANN Koska Agency Limited | Administrative & support | 2003 |
| ANN WO Photography Limited | Administrative & support | 2013 |