| AIM Safety Limited | Professional & scientific | 2014 |
| Aimee Jane Dance Company Ltd | Arts & recreation | 2021 |
| Ainsworth Building Holding Company Ltd | Construction | 2021 |
| Ainsworth Civils & Engineering Limited | Construction | 2004 |
| Ainsworth Holdings Limited | Extraterritorial | 2007 |
| Aintree Property Management Company Limited | Real estate | 2024 |
| Aion Spedition Ltd | Transport & logistics | 2025 |
| Air Conditioning & Engineering Services Limited | Construction | 2010 |
| Air Conditioning & Mech Services Ltd | Construction | 2015 |
| Air Reach Limited | Manufacturing | 2015 |
| Air Star Limited | Financial services | 2017 |
| Air Transport Publications Ltd | Professional & scientific | 2001 |
| Airborne Holdings Limited | Professional & scientific | 2021 |
| Airdropbox Limited | Manufacturing | 2013 |
| Airnesco Group Ltd | Manufacturing | 1996 |
| Airnesco Limited | Professional & scientific | 1979 |
| Airport-Connection Sevenoaks Ltd | Transport & logistics | 2026 |
| Airsoftgreatbritain Limited | Arts & recreation | 2015 |
| AIS Property Investments & Management Limited | Real estate | 2025 |
| Aissatouvtrans Ltd | Transport & logistics | 2020 |
| Aiston Plumbing & Heating Limited | Construction | 2022 |
| Aiston Property Services Limited | Construction | 2022 |
| Aiteo Consulting Limited | Professional & scientific | 2006 |
| Aivaras Leckas Ltd | Transport & logistics | 2018 |
| Aizanic Ltd | Information & communication | 2017 |
| AJ Haffenden Electrical Services Ltd | Construction | 2014 |
| AJ Marketing Ltd | Professional & scientific | 2026 |
| AJ Property Acquisitions Ltd | Real estate | 2021 |
| AJ Wedge Building and Maintenance Ltd | Construction | 2013 |
| Ajatar Ltd | Manufacturing | 2024 |
| AJC Productions Ltd | Information & communication | 2018 |
| AJD Print Ltd | Administrative & support | 2022 |
| AJH (Kent) Limited | Wholesale & retail | 2012 |
| AJH Commercial Limited | Real estate | 2017 |
| AJJ 66 Ltd | Hospitality | 2019 |
| AJM Jewellery Ltd | Manufacturing | 2023 |
| AJN Fire Safety Ltd | Public administration | 2019 |
| Ajobe Construction Services Ltd | Construction | 2024 |
| AJP Plant Limited | Administrative & support | 2017 |
| Ajp&H Ltd | Construction | 2018 |
| AJS Decor Limited | Construction | 2002 |
| AK Access (Medway) Ltd | Construction | 2024 |
| AK Engineering (Medway) Ltd | Wholesale & retail | 2017 |
| AK FFF Coaching LLP | | 2025 |
| Ak-Glass Windows and Doors Ltd | Construction | 2025 |
| Akehurst Properties Limited | Real estate | 2021 |
| Akelom Barbers Ltd | Other services | 2018 |
| Akfum Network Limited | Information & communication | 2013 |
| Akin Whites Consultancy Ltd | Wholesale & retail | 2020 |
| Akiventures Ltd | Wholesale & retail | 2026 |
| Akord Wealth Management Ltd | Real estate | 2018 |
| Akranim Limited | Professional & scientific | 2008 |
| Aksa Foods Europe Limited | Hospitality | 2014 |
| Aktive ID Consulting Ltd | Professional & scientific | 2023 |
| AL Brickwork Solution Ltd | Construction | 2024 |
| Al-Rayaan Ltd | Real estate | 2019 |
| ALA Shawaromania Ltd | Hospitality | 2026 |
| Aladdin Shawarma & Rotisserie Ltd | Hospitality | 2024 |
| Alamir-Group Ltd | Manufacturing | 2023 |
| Alan Baxter Partnership LLP | | 2006 |
| Alan Douglas Plant and Transport Limited | Administrative & support | 2005 |
| Alan Firmin Limited | Transport & logistics | 1957 |
| Alanco Agricultural Limited | Manufacturing | 1986 |
| ALB Mastic Sealant Ltd | Construction | 2019 |
| Albany Funerals Limited | Other services | 2009 |
| Albemarle Riverside Management Ltd | Households | 2021 |
| Albino Ltd | Manufacturing | 2026 |
| Albion House RTM Company Limited | Households | 2018 |
| Albion RTW Limited | Other services | 2010 |
| Albodross Ltd | Public administration | 2019 |
| Albtrad Ltd | Wholesale & retail | 2022 |
| ALC Drill Limited | Mining & quarrying | 2021 |
| Alchemy Mediation Ltd | Administrative & support | 2012 |
| Alcorn Glazing Ltd | Construction | 2016 |
| ALD Access Solutions Ltd | Construction | 2018 |
| Alder Homes Limited | Construction | 2016 |
| Aldergate Trade Ltd | Wholesale & retail | 2018 |
| Alderwood Holdings Limited | Professional & scientific | 2007 |
| Alex Kaboye Ltd | Construction | 2016 |
| Alex Nicholl Compressors Limited | Wholesale & retail | 2016 |
| Alex Tenters Photography Limited | Professional & scientific | 2019 |
| Alex&Nico Limited | Transport & logistics | 2025 |
| Alexander Harris & Associates LLP | | 2010 |
| Alexander Isaac Consulting Limited | Professional & scientific | 2018 |
| ALEXANDIKIRAW11 Ltd | Wholesale & retail | 2025 |
| Alexandrafreitas Limited | Health & social care | 2015 |
| Alexia Group Ltd | Construction | 2015 |
| Alexia Lescure Ltd | Health & social care | 2014 |
| Alfatrack Limited | Administrative & support | 2013 |
| Alfergy Ltd | Information & communication | 2026 |
| Alfies Fish Bar and Kebab Ltd | Hospitality | 2026 |
| Alfred James Ltd | Real estate | 2024 |
| Algarve Properties Limited | Professional & scientific | 1984 |
| Algorethics Ltd | Education | 2021 |
| ALI Medica Ltd | Health & social care | 2023 |
| ALI Wahab Ltd | Public administration | 2021 |
| Ali's Dance Limited | Arts & recreation | 2010 |
| Alicus Ltd | Information & communication | 2019 |
| Alider Ltd | Other services | 2025 |
| Align Pilates Studio Ltd | Arts & recreation | 2023 |