| Adoeclat Limited | Real estate | 2023 |
| ADR Sustainability Ltd | Professional & scientific | 2011 |
| ADR Sustainable Clothing Ltd | Wholesale & retail | 2024 |
| Adrian James Nutrition Ltd | Professional & scientific | 2011 |
| Adro Property Ltd | Real estate | 2019 |
| Adroit Financial Consulting Limited | Professional & scientific | 2015 |
| Advaitha Consulting UK Limited | Information & communication | 2010 |
| Advaitha Property Management Ltd | Real estate | 2019 |
| Advance Car Care Ltd | Wholesale & retail | 2018 |
| Advanced Climate Engineering Ltd | Construction | 2017 |
| Advanced Damp Ltd | Construction | 2021 |
| Advanced Furniture Concepts Ltd. | Manufacturing | 2024 |
| Advanced Human Performance Ltd | Health & social care | 2025 |
| Advanced Locums Limited | Health & social care | 2008 |
| Advanced Sheet Metal Engineering Limited | Manufacturing | 2007 |
| Advanced Vehicle Diagnostics Limited | Wholesale & retail | 2025 |
| Advant Technology Limited | Professional & scientific | 2014 |
| Advantage Worldwide (UK) Limited | Transport & logistics | 2002 |
| Advante Medical Ltd | Health & social care | 2008 |
| Advent Press Limited | Manufacturing | 2011 |
| Adventure Africa Ltd | Administrative & support | 2025 |
| Adweek UK Limited | Information & communication | 2020 |
| Ady&Dany Transport Ltd | Transport & logistics | 2026 |
| AEA Medical Ltd | Health & social care | 2023 |
| Aean Ltd | Real estate | 2023 |
| Aegle Consulting Limited | Professional & scientific | 2019 |
| Aequalis Verde IP Limited | Financial services | 2015 |
| Aequalis Verde Limited | Professional & scientific | 2015 |
| Aerial Camera Systems Limited | Information & communication | 1979 |
| Aeroglow Limited | Extraterritorial | 2014 |
| Aeropropel Limited | Transport & logistics | 2018 |
| Aeros Partners Ltd | Financial services | 2012 |
| Aerotec Aviation Services Limited | Professional & scientific | 2009 |
| AES Maintenance Limited | Construction | 2008 |
| Aesthetic Lifestyle Limited | Wholesale & retail | 2024 |
| Aesthetic Nursing Services Ltd | Health & social care | 2022 |
| Aettrum Limited | Real estate | 2020 |
| Aexis Revolution Ltd | Information & communication | 2026 |
| AF Property Ltd | Real estate | 2018 |
| Affection Care Services Ltd | Health & social care | 2018 |
| Affectionate Loving Care Ltd | Health & social care | 2021 |
| Affinity Hayes Ltd | Real estate | 2024 |
| Affording Assets Ltd | Construction | 2024 |
| Affording IT Limited | Information & communication | 2005 |
| AFM Software Consultancy Ltd | Information & communication | 2017 |
| Afreen Property Ltd | Real estate | 2020 |
| Afrimart Global Limited | Wholesale & retail | 2025 |
| Aftercare Response Limited | Wholesale & retail | 2018 |
| AG 24/7 Recovery & Jumpstart Ltd | Transport & logistics | 2026 |
| AG Concierge Limited | Wholesale & retail | 2018 |
| AG Energy Solutions Ltd | Construction | 2013 |
| AG Leasing Limited | Administrative & support | 2018 |
| AG Path Finder Limited | Other services | 2021 |
| AG Stoica Construction Ltd | Construction | 2021 |
| Agateo Materials Ltd | Wholesale & retail | 2021 |
| AGE Painting & Decorating Ltd | Construction | 2025 |
| Agency AID CIC | Other services | 2024 |
| Agent Shield Ltd | Information & communication | 2026 |
| AGH Film Ltd | Information & communication | 2023 |
| Agile Infrastructure Consulting Ltd | Professional & scientific | 2018 |
| Agile Revolution Limited | Information & communication | 2015 |
| Agility Accounting Ltd | Professional & scientific | 2018 |
| Agilitydelivered Limited | Information & communication | 2022 |
| Agillo Limited | Information & communication | 2023 |
| Agis Executive Ltd | Transport & logistics | 2021 |
| AGL Interiors Ltd | Wholesale & retail | 2021 |
| AGR Real Estates Ltd | Construction | 2025 |
| Agri Samplers Limited | Manufacturing | 2019 |
| Agrigum International Limited | Wholesale & retail | 2007 |
| Agyps Holdings Ltd | Financial services | 2024 |
| AH Cars Limited | Wholesale & retail | 2026 |
| AH Estatez Ltd | Real estate | 2025 |
| AH Halal Meat UK Ltd | Wholesale & retail | 2025 |
| AH Sustainability Ltd | Professional & scientific | 2026 |
| AH Tyres and Autos Limited | Wholesale & retail | 2026 |
| AHA and Sons Limited | Health & social care | 2015 |
| AHB Autos Ltd | Wholesale & retail | 2025 |
| Ahil Ajaz Ltd | Manufacturing | 2026 |
| AI by Boden Limited | Professional & scientific | 2011 |
| AI for H Ltd | Information & communication | 2025 |
| AI Infrastructure Ltd | Information & communication | 2026 |
| AI Kars Ltd | Wholesale & retail | 2025 |
| AI Solar Ltd | Construction | 2022 |
| AI Test Group Ltd | Information & communication | 2014 |
| AI Trade Solutions Limited | Wholesale & retail | 2024 |
| AIA Property Services Limited | Construction | 2023 |
| Aida Foods Ltd | Hospitality | 2024 |
| Aidos Global Limited | Construction | 2019 |
| Aihl Ltd | Wholesale & retail | 2026 |
| Aihl Vehicle Hire Ltd | Wholesale & retail | 2012 |
| AIM Alternative Provision Limited | Education | 2025 |
| AIM Apartments Ltd | Real estate | 2024 |
| AIM Storylab Ltd | Education | 2024 |
| Aimos Group Limited | Extraterritorial | 2023 |
| AIN Hotels Ltd | Hospitality | 2020 |
| Aine Niamh Butler Ltd | Extraterritorial | 2025 |
| Ainsley Harris Ltd | Professional & scientific | 2010 |
| Air Odyssea Limited | Professional & scientific | 2024 |
| Air Quality Services Ltd | Construction | 1991 |
| Air Vent Technology Limited | Manufacturing | 1996 |