| Ahonabir Edutech Consultancy Ltd | Professional & scientific | 2025 |
| Ahsquare Global Ventures Ltd | Health & social care | 2019 |
| AI Business Consultants Limited | Information & communication | 2024 |
| Ai-Sys Labs Limited | Information & communication | 2020 |
| Aiai Properties Ltd | Hospitality | 2025 |
| Aicp Limited | Administrative & support | 2026 |
| AIF Management Limited | Professional & scientific | 2006 |
| Aigurumeditation Ltd | Information & communication | 2026 |
| Aiimsearch Ltd | Information & communication | 2025 |
| AIM Consultancy and Construction Services Ltd | Real estate | 2020 |
| AIM Contracts Group Ltd | Transport & logistics | 2023 |
| Aimos Jewellery Ltd | Wholesale & retail | 2023 |
| Aion Health Care & Support Services Limited | Health & social care | 2025 |
| Air and Fluid Systems Limited | Construction | 2011 |
| Air Note International Ltd | Manufacturing | 2024 |
| Air Pumping Limited | Manufacturing | 2000 |
| Air Yachting Limited | Other services | 2024 |
| Airpitch International Ltd | Arts & recreation | 2023 |
| Airport Marketing Limited | Professional & scientific | 2016 |
| Airtech Analysis Ltd | Professional & scientific | 1990 |
| Airvi-Uk Limited | Information & communication | 2019 |
| Airways AC Ltd | Energy | 2023 |
| Airy Air Conditioning Ltd | Energy | 2024 |
| AIS Vets Limited | Professional & scientific | 2009 |
| AIW Energy Assessors Ltd | Professional & scientific | 2011 |
| Aiyfin Limited | Administrative & support | 2025 |
| AJ Batty Services Ltd | Administrative & support | 2026 |
| AJ Blueprints Ltd | Professional & scientific | 2024 |
| AJ Fire and Security Ltd | Construction | 2005 |
| AJ Loft Rooms Roofing Ltd | Construction | 2021 |
| AJ Safe Guard Limited | Professional & scientific | 2025 |
| AJ Sears Advisory & Consultancy Limited | Professional & scientific | 2025 |
| AJ Tints Ltd | Wholesale & retail | 2024 |
| AJ Watches Limited | Wholesale & retail | 2019 |
| Ajaw Consultancy Limited | Education | 2021 |
| AJB Scaffolding Limited | Construction | 2005 |
| AJC Johnson Controls Limited | Manufacturing | 1936 |
| AJM Matra Investments Limited | Real estate | 2025 |
| AJN Supplies Ltd | Wholesale & retail | 2023 |
| Ajolopo Limited | Administrative & support | 2017 |
| AJR Autos Ltd | Real estate | 2002 |
| AJR Essex Transport Ltd | Transport & logistics | 2025 |
| AJS Finance & Consulting Ltd | Professional & scientific | 2026 |
| AJS FM Ltd | Construction | 2016 |
| AJS Global Goods Ltd | Wholesale & retail | 2025 |
| AJS Group Services Ltd | Real estate | 2019 |
| AJS Ltd | Wholesale & retail | 1994 |
| AK Aviation Ltd | Manufacturing | 2025 |
| AK Companies Ltd | Professional & scientific | 2021 |
| AK Electrical (Rayne) Limited | Manufacturing | 2007 |
| AK Orthopedics Ltd | Health & social care | 2012 |
| AK Wholesalers Limited | Other services | 2017 |
| Akag Limited | Information & communication | 2016 |
| AKB Transformations Ltd | Information & communication | 2023 |
| Akiranet Ltd | Professional & scientific | 2015 |
| Akkus Chelmer Ltd | Real estate | 2021 |
| AKN Developments Ltd | Financial services | 2026 |
| AKN Infrastructure Ltd | Construction | 2026 |
| Akorn ASH Limited | Professional & scientific | 2011 |
| Akoss Ltd | Professional & scientific | 2025 |
| Akotia Holdings Limited | Financial services | 2023 |
| AKS68 Ltd | Hospitality | 2026 |
| Akts Recruitment Limited | Administrative & support | 2022 |
| AKW Limited | Real estate | 2023 |
| Akwab Ltd | Wholesale & retail | 2023 |
| AL Bakar Estate Limited | Real estate | 2012 |
| Al-Fazal Private Ltd | Transport & logistics | 2020 |
| Al-Hashemi Ltd | Real estate | 2021 |
| Al-Sarah Limited | Administrative & support | 2023 |
| Alafar Ltd | Health & social care | 2019 |
| Alan Blumlein Ltd | Information & communication | 2012 |
| Alan J Ostridge Holdings Limited | Professional & scientific | 2019 |
| Alan Johnson Accountancy Ltd | Professional & scientific | 2003 |
| Alangeorge Car Wash Ltd | Administrative & support | 2025 |
| Alastair Clayton Ltd | Administrative & support | 2022 |
| Alba Sunrise Ltd | Real estate | 2012 |
| Albert Odulele Outreach (AOO) Limited | Other services | 2022 |
| Albeth Ltd | Construction | 2024 |
| Albi Engineering Ltd | Construction | 2020 |
| Albie Lily Limited | Real estate | 2026 |
| Albireo Energy International Limited | Financial services | 2021 |
| Albo Property Management Limited | Real estate | 2023 |
| Albright Construction Ltd | Construction | 2010 |
| Alco Real Estate Limited | Real estate | 2025 |
| Alderton Associates Limited | Professional & scientific | 2004 |
| ALE NAT Trans Ltd | Transport & logistics | 2025 |
| Alegup.Co.Uk Ltd | Extraterritorial | 2021 |
| Alein Investments Limited | Administrative & support | 2015 |
| Alessio & Laura Maugeri Ltd | Hospitality | 2020 |
| Alex Mcghee Creative Limited | Professional & scientific | 2018 |
| Alexander Lane Management Company Limited | Households | 2025 |
| Alexander Luke Limited | Financial services | 2022 |
| Alexander Mews Meadow Limited | Professional & scientific | 1999 |
| Alexander Technique Education UK Ltd | Other services | 2013 |
| Alexandra Williams Commercial and Residential Estates Ltd | Construction | 2024 |
| Alexis Healthcare Services Limited | Health & social care | 2025 |
| Alexvl Limited | Wholesale & retail | 2019 |
| Alfa Legal Ltd | Professional & scientific | 2018 |
| Alfa Safety Ltd | Professional & scientific | 2019 |
| Alfamill Limited | Construction | 2021 |