| Aethelstan Limited | Construction | 2017 |
| Aevp Services Limited | Other services | 2014 |
| AEY Cleaning Ltd | Administrative & support | 2025 |
| AFC Construction Services Ltd | Construction | 2026 |
| AFC Welwyn C.I.C. | Arts & recreation | 2023 |
| Affinity Staff Limited | Administrative & support | 2021 |
| Affluence Consultancy Ltd | Other services | 2022 |
| Affordable Locks Ltd | Construction | 2012 |
| Afin Consultancy CIC | Professional & scientific | 2025 |
| Afortiori BIO Limited | Professional & scientific | 2025 |
| African Things Limited | Manufacturing | 2013 |
| Afro Asian Foods Ltd | Extraterritorial | 2025 |
| AFS Drains Ltd | Administrative & support | 2020 |
| AG Garden Services & Design Limited | Administrative & support | 2017 |
| Ag&Kk Services Ltd | Construction | 2013 |
| AGA Firestopping Ltd | Public administration | 2025 |
| Agape Generation International Church UK | Education | 2023 |
| Agapiou Westminster Partnership LLP | | 2009 |
| AGB Design Ltd | Professional & scientific | 2024 |
| Agent Hybrid Limited | Real estate | 2016 |
| Aggarwal Commercial Enterprises (Ace) Limited | Health & social care | 2016 |
| Aggarwal Commercial Properties (ACP) Ltd | Real estate | 2019 |
| Agility Impact Holdings Limited | Administrative & support | 2019 |
| AGJ Business Services Ltd | Professional & scientific | 2014 |
| AGJ Parent Company Ltd | Professional & scientific | 2014 |
| AGL Bespoke Upvc Limited | Construction | 2022 |
| AGL Upvc Sprayers Limited | Construction | 2017 |
| Agno Cleaning and Restoration Ltd | Administrative & support | 2018 |
| AGR Electrical Services Ltd | Construction | 2021 |
| Agradicer Limited | Health & social care | 2025 |
| Agram Zalar Film Production Ltd | Information & communication | 2023 |
| AH Indian Spice Limited | Hospitality | 2025 |
| Ahir Estates Ltd | Financial services | 2023 |
| Ahir Investments Ltd | Real estate | 2019 |
| Ahir Properties Limited | Real estate | 2017 |
| Ahmed Khan Limited | Education | 2025 |
| AI Digital Marketing Ltd | Information & communication | 2024 |
| AI Generation Consultancy Ltd | Information & communication | 2024 |
| AI1 Holdings Ltd | Real estate | 2021 |
| Aida Burgers Ltd. | Hospitality | 2020 |
| Aide Ltd | Professional & scientific | 2023 |
| Aigoma Ltd | Other services | 2012 |
| AIM Securities Limited | Administrative & support | 1967 |
| Aime Care Limited | Health & social care | 2024 |
| AIR2ZOOM Consulting Limited | Professional & scientific | 2022 |
| Airbus UK Pension Trustee | Administrative & support | 2018 |
| Aircraft Support Solutions Ltd | Manufacturing | 2020 |
| Airmen Technical Services Limited | Other services | 2024 |
| Airpads Limited | Real estate | 2020 |
| Airstream TDH Ltd | Hospitality | 2021 |
| AJ Premier Ltd | Professional & scientific | 2016 |
| AJ4 Electrical Ltd | Construction | 2023 |
| Ajfoodsstevenage Ltd | Hospitality | 2025 |
| AJK Building Ltd | Construction | 2024 |
| AJV Fire Protection Ltd | Construction | 2021 |
| AK Design Solutions Limited | Professional & scientific | 2016 |
| AK Rose Holdings Ltd | Financial services | 2025 |
| AK Tearle Mechanical Services Ltd | Construction | 2024 |
| AK58GUT Ltd | Health & social care | 2021 |
| Akbary Cars Ltd | Wholesale & retail | 2014 |
| AKC Care Limited | Health & social care | 2018 |
| AKJ Homes Limited | Administrative & support | 2025 |
| AKS Developer Ltd | Professional & scientific | 2022 |
| Akshay Ventures Limited | Real estate | 2015 |
| Aktw Limited | Wholesale & retail | 2015 |
| Akumina UK Ltd | Administrative & support | 2018 |
| Akyil Ltd | Real estate | 2025 |
| AL Mikhdham Ltd | Wholesale & retail | 2021 |
| Alban Moves Limited | Extraterritorial | 2007 |
| Albert Street 1963 Limited | Extraterritorial | 2013 |
| Alcas Limited | Information & communication | 1995 |
| Alchemmy Consulting Limited | Administrative & support | 2012 |
| Alchemy 1234 Limited | Wholesale & retail | 1985 |
| Alchemy Commercial Finance Limited | Financial services | 2006 |
| Alchemy Integrated Waste Solutions Ltd | Water & waste | 2023 |
| Alchemy Metals Group Limited | Water & waste | 2014 |
| Alchemy Metals Infrastructure Limited | Water & waste | 2014 |
| Alchemy Metals Limited | Water & waste | 1993 |
| Alchemy Metals Properties Limited | Real estate | 2014 |
| Alchemy Metals Solutions Limited | Water & waste | 2014 |
| Alchemy Metals UK Limited | Professional & scientific | 2006 |
| Alchemy-Phoenix UK Ltd | Information & communication | 2014 |
| Alcoreza Ltd | Health & social care | 2025 |
| Alex & Paulina Construction Ltd | Construction | 2024 |
| Alex Bassford Ltd | Information & communication | 2026 |
| Alexander Accountants Limited | Professional & scientific | 2010 |
| Alexander and Winthorpe Property Group Ltd | Real estate | 2021 |
| Alexander Davis Properties Ltd | Other services | 2018 |
| Alexander Holness Ltd | Professional & scientific | 2018 |
| ALEXANDRA2023 Ltd | Construction | 2025 |
| Alfassa Holdings Ltd | Financial services | 2019 |
| Alfredopasta London Ltd | Hospitality | 2025 |
| Alghero Estates Limited | Extraterritorial | 2009 |
| Alia Productions Ltd | Arts & recreation | 2024 |
| Aligned Eleven Ltd | Other services | 2022 |
| Alina Bookkeeping Limited | Professional & scientific | 2021 |
| Alina Care Services Ltd | Administrative & support | 2023 |
| ALL Groovy VFX Ltd | Information & communication | 2023 |
| ALL My Business Limited | Other services | 2019 |
| ALL Scrap Metal & Recycling Limited | Water & waste | 2014 |