| Agrova Limited | Wholesale & retail | 2025 |
| AGS Pension Trustee Limited | Financial services | 2011 |
| AGU Lifestyle Ltd | Wholesale & retail | 2025 |
| AH Home Improvements LLP | | 2026 |
| Ahana Systems Limited | Information & communication | 2011 |
| AHENCIAKO2 Ltd | Health & social care | 2014 |
| AHW Commerce Ltd | Wholesale & retail | 2023 |
| Aikonexia Ltd | Construction | 2025 |
| Air Sea Forwarding Ltd | Transport & logistics | 2017 |
| Airo Clean Ltd | Administrative & support | 2025 |
| AIS Courier Services Limited | Transport & logistics | 2022 |
| AIS Express Limited | Transport & logistics | 2020 |
| AJ Clean House Ltd | Administrative & support | 2019 |
| AJF Bespoke Ltd | Construction | 2023 |
| Ajgk Holdings Limited | Financial services | 2016 |
| AJH GAS Services (Berkshire) Limited | Construction | 2017 |
| Ajilex Ltd | Information & communication | 2007 |
| AJP Locums Limited | Health & social care | 2009 |
| AJP Statistics Ltd | Professional & scientific | 2023 |
| AJS Roofing Limited | Administrative & support | 2012 |
| Ajws-Cards Ltd | Wholesale & retail | 2025 |
| AK Prime Residential Ltd | Real estate | 2024 |
| AK Properties Solutions Limited | Households | 2026 |
| AK Teach Ltd | Education | 2021 |
| AKH Solutions Limited | Professional & scientific | 2013 |
| Akisou Property Ltd | Real estate | 2026 |
| Akshaysales Limited | Wholesale & retail | 2025 |
| AL Consulting Services Limited | Information & communication | 2016 |
| Alacrity Search & Consulting Limited | Administrative & support | 2025 |
| Alamo Arms Ltd | Other services | 2020 |
| Alan Fuller Plumbing & Heating Limited | Construction | 2017 |
| ALB Logistics Ltd | Transport & logistics | 2016 |
| ALB Network Cabling Solutions Ltd | Construction | 2025 |
| Albion Groundworkers Ltd | Construction | 2021 |
| Albovi Group Ltd | Wholesale & retail | 2024 |
| ALE Wyzerka! Polish Food Ltd | Hospitality | 2024 |
| Alegri Trade Ltd. | Wholesale & retail | 2017 |
| Alex Maltman Ltd | Wholesale & retail | 2022 |
| Alfa Chemicals Group Limited | Financial services | 2019 |
| Algolabs Ltd | Professional & scientific | 2022 |
| ALI Kebab Fast Food Ltd | Hospitality | 2018 |
| Alien Abduction Limited | Information & communication | 2025 |
| Alii AFT Ltd | Transport & logistics | 2022 |
| Alin Curteza Groundwork Ltd | Construction | 2020 |
| Allegis Global Solutions Limited | Information & communication | 1998 |
| Allegis Group (UK) Holdings II Limited | Information & communication | 2011 |
| Allegis Group Limited | Information & communication | 1993 |
| Allegis Services Holdings Limited | Financial services | 2019 |
| Allepaznokcie UK Ltd | Wholesale & retail | 2020 |
| Alliance Drug Development Limited | Professional & scientific | 2010 |
| Allmeta Group UK Ltd | Wholesale & retail | 2024 |
| Allucent (UK) Limited | Professional & scientific | 1995 |
| Allucent Group (UK) Limited | Professional & scientific | 2002 |
| Alra Estates Limited | Real estate | 2024 |
| Alternative Laboratory Ltd | Information & communication | 2025 |
| Altiora Estates Limited | Real estate | 2021 |
| Altiora Group Ltd | Financial services | 2022 |
| Altiora Investments Limited | Construction | 2010 |
| Altiz Limited | Public administration | 2023 |
| Altra Trading Ltd | Wholesale & retail | 2025 |
| Always Techy Ltd | Information & communication | 2026 |
| Alx-Photo Ltd | Arts & recreation | 2023 |
| Alysha CAN Ltd | Professional & scientific | 2020 |
| Alzirstar Limited | Information & communication | 2013 |
| Amafhh Medics Limited | Health & social care | 2010 |
| Amalgam Builders Limited | Construction | 2019 |
| Amazing Grace Shops Ltd | Wholesale & retail | 2017 |
| Amazing Rose Care Limited | Health & social care | 2022 |
| Amazwe Quality Cousultancy Limited | Professional & scientific | 2024 |
| Ambar Jewels Ltd | Manufacturing | 2024 |
| Amber Mystery Ltd | Wholesale & retail | 2021 |
| Ambersmart Limited | Financial services | 2002 |
| Amerlan Limited | Financial services | 2018 |
| Amevés Limited | Wholesale & retail | 2025 |
| AMF Automotive Solutions Ltd | Wholesale & retail | 2020 |
| Amglass&Mirror Ltd | Construction | 2012 |
| Amira Trans (UK) Ltd | Transport & logistics | 2013 |
| Amish Patel Consulting Ltd | Professional & scientific | 2021 |
| AMK Clothing Limited | Wholesale & retail | 2023 |
| Amloga Energy Limited | Wholesale & retail | 2017 |
| Amphora Research Systems Limited | Information & communication | 2003 |
| Amphora Solutions Ltd | Professional & scientific | 2014 |
| Amps Physiotherapy Ltd | Health & social care | 2015 |
| AMR IT Support Ltd | Information & communication | 2019 |
| Amradnet UK Diagnostic Services Ltd | Health & social care | 2023 |
| AMS3D Ltd | Manufacturing | 2025 |
| AMV Equity Investments Limited | Mining & quarrying | 2015 |
| AMY Schlachter Ltd | Professional & scientific | 2014 |
| AN Frozen'N' Live Food Limited | Administrative & support | 2017 |
| Anas Traders Retail Ltd | Wholesale & retail | 2025 |
| Anatello Limited | Professional & scientific | 1994 |
| Anchor International Services Ltd | Professional & scientific | 2015 |
| Anders Homes Limited | Real estate | 2023 |
| Andrew Grosvenor Ltd | Information & communication | 2009 |
| Andrew Hall Electrical Ltd | Construction | 2020 |
| Andrew MAC Training Ltd | Administrative & support | 2023 |
| Andrews & Arnold (Numbers) Ltd | Extraterritorial | 2003 |
| Andrews & Arnold Ltd | Information & communication | 1997 |
| Andrews Arnold Limited | Extraterritorial | 2020 |
| Andron Construction Ltd | Construction | 2015 |