| Aejl Ltd | Construction | 2025 |
| Aejl Properties Ltd | Real estate | 2026 |
| Aelprop Ltd | Real estate | 2016 |
| Aepex Insights Ltd | Professional & scientific | 2026 |
| AER Soleir Management (UK) Limited | Administrative & support | 2021 |
| Aerial Alien Limited | Information & communication | 2015 |
| Aerial Construction Services Ltd | Professional & scientific | 2020 |
| Aerivox Holdings Ltd | Extraterritorial | 2026 |
| Aesthetic by Diana Ltd | Other services | 2025 |
| Aesthetic Medical Supplies Limited | Manufacturing | 2020 |
| Aesy Enterprise Ltd | Information & communication | 2024 |
| Aeternum Property Holdings Limited | Real estate | 2026 |
| Aethelos Ltd | Manufacturing | 2025 |
| AF Consultancy Limited | Administrative & support | 2024 |
| AF Logistics Ltd | Transport & logistics | 2025 |
| Afaq Al-Rida for Industry Ltd | Manufacturing | 2025 |
| Affinity Associates Isaacs & Co Limited | Professional & scientific | 2016 |
| Affinity Healthcare PVT Ltd | Health & social care | 2026 |
| Affinity Renewables Limited | Water & waste | 2015 |
| Affinix Autos Ltd | Wholesale & retail | 2025 |
| Affordable Doors Ltd | Wholesale & retail | 2022 |
| Affordable Vehicle Maintenance Solutions Limited | Transport & logistics | 2016 |
| Affordable Web Design Ltd | Information & communication | 2025 |
| AFL Solutions Ltd | Information & communication | 2012 |
| Afna Services Ltd | Real estate | 2025 |
| African Beacon Centre | Public administration | 2025 |
| African Community UK CIC | Information & communication | 2018 |
| Afridis Ltd | Wholesale & retail | 2023 |
| Afripantry Limited | Wholesale & retail | 2025 |
| Afriye Limited | Health & social care | 2014 |
| Afro Foodhub Limited | Hospitality | 2024 |
| Afterglow Sunbeds Ltd | Other services | 2022 |
| Afterglow Tanning Auckley Limited | Other services | 2025 |
| AG Asset Management (Yorkshire) Ltd | Real estate | 2017 |
| AG Auto FIX Ltd | Wholesale & retail | 2025 |
| AG Plastering Yorkshire Ltd | Construction | 2019 |
| AG Property Matters Ltd | Real estate | 2024 |
| AGE UK Doncaster | Health & social care | 1999 |
| Agemaspark Holdings Limited | Manufacturing | 2017 |
| Agemaspark Ltd | Manufacturing | 2002 |
| Agency Club Ltd | Administrative & support | 2020 |
| Agency Endoscopy Limited | Health & social care | 2020 |
| Agency Signs Direct Ltd | Administrative & support | 2009 |
| AGF Consultants Limited | Construction | 2025 |
| AGG Facades Ltd | Construction | 2020 |
| Aggre One Ltd | Manufacturing | 2019 |
| Aggregates R US Ltd | Wholesale & retail | 2008 |
| Agile Material Handling Ltd | Professional & scientific | 2026 |
| Agile Modular Limited | Real estate | 2023 |
| AGL Telecoms Limited | Professional & scientific | 2012 |
| AGM Auto Ltd | Wholesale & retail | 2025 |
| AGM Safety Ltd | Professional & scientific | 2012 |
| AGM Trading Limited | Wholesale & retail | 2025 |
| Agnes Property Solutions Ltd | Real estate | 2024 |
| Agnes Tattoo Ltd | Other services | 2025 |
| Agri Asset LLP | | 2025 |
| Agriargo UK Limited | Wholesale & retail | 2008 |
| Agrimac (NTH) Ltd | Agriculture & fishing | 2016 |
| Agriscope Limited | Administrative & support | 2014 |
| Agriscope Services Limited | Manufacturing | 2025 |
| Agrivolta Ltd | Professional & scientific | 2026 |
| AGS Project Services Limited | Professional & scientific | 2026 |
| AGT Parts Ltd | Wholesale & retail | 2025 |
| AH Fire Ltd | Professional & scientific | 2019 |
| AH Mortgage Co Limited | Financial services | 2026 |
| AH Property Ltd | Real estate | 2025 |
| AH Sales Ltd | Administrative & support | 2017 |
| AH Security & Training Ltd | Administrative & support | 2019 |
| Ah-Hah Ltd | Extraterritorial | 2009 |
| Ahad Tandoori Restaurant (Gosforth) Limited | Hospitality | 2018 |
| Ahfa Ltd | Health & social care | 2016 |
| Ahmad Tahir Ltd | Wholesale & retail | 2026 |
| Ahoy There Limited | Transport & logistics | 2021 |
| AHP Consultancy Limited | Information & communication | 2018 |
| Ahppy Hydro Limited | Wholesale & retail | 2011 |
| Ahyan Capital Limited | Financial services | 2017 |
| AI Commodities Exchange Ltd | Financial services | 2025 |
| Aiai Studios Ltd | Professional & scientific | 2021 |
| Aiai-Artificialintelligentassistantinlife Ltd | Extraterritorial | 2025 |
| AIB Cardiology Consultant Limited | Health & social care | 2022 |
| Aice Clinical Psychology Services Ltd | Health & social care | 2018 |
| Aidology Training Company Limited | Education | 2025 |
| Aidplus Source (UK) Co., Limited | Extraterritorial | 2005 |
| AIL Beta Holding Limited | Financial services | 2001 |
| Aileen Abbott Hearing Care Ltd | Wholesale & retail | 2022 |
| Aill Trust Corporation Limited | Extraterritorial | 2021 |
| AIM Management Junction Ltd | Hospitality | 2025 |
| Aimee Systems Limited | Information & communication | 2023 |
| Ainger Investments Limited | Professional & scientific | 2014 |
| Aintree Investments Ltd | Real estate | 2022 |
| Air Education Limited | Information & communication | 2024 |
| Air Force Renewables Ltd | Construction | 2025 |
| Air Goods Limited | Wholesale & retail | 2025 |
| Air Haulage Ltd | Transport & logistics | 2023 |
| Air Haus Meadowhall Limited | Arts & recreation | 2026 |
| Air Waze UK Ltd | Construction | 2023 |
| Airhalf Limited | Manufacturing | 1999 |
| Airmyn Developments Limited | Construction | 2026 |
| Airport Transfer Grantham Ltd | Extraterritorial | 2023 |
| Airstream Events Ltd | Hospitality | 2023 |