| Aslan Services Limited | Real estate | 2024 |
| ASM Software Solutions Ltd | Wholesale & retail | 2017 |
| Asoa Consulting Limited | Professional & scientific | 2024 |
| Asongs Music Publishing LLP | | 2010 |
| Asora Limited | Information & communication | 2018 |
| Aspaceupgrade Ltd | Construction | 2024 |
| Aspen Property Consultants Limited | Real estate | 2002 |
| Aspire Sports & Cultural Trust | Arts & recreation | 2008 |
| Associate Worldwide Limited | Professional & scientific | 2020 |
| Aster Media Group Limited | Other services | 2026 |
| Asteroid Media Productions Limited | Information & communication | 2025 |
| Astir (Investments) Ltd | Real estate | 2021 |
| Aston Complete Services Ltd | Manufacturing | 2013 |
| Astra Fintech Limited | Information & communication | 2026 |
| Astrid James Property Services Ltd | Real estate | 2023 |
| Astriven Ltd | Real estate | 2024 |
| AT Fruit Limited | Professional & scientific | 2014 |
| Ateampj Ltd | Hospitality | 2019 |
| Atelier DE Linde Ltd | Professional & scientific | 2022 |
| Atelier Fitzrovia Ltd | Other services | 2025 |
| ATELIER13 Limited | Wholesale & retail | 2018 |
| Athena Business Support Limited | Administrative & support | 2024 |
| Athlft Ltd | Education | 2025 |
| ATI Capital Ltd | Wholesale & retail | 2024 |
| Atkinson Digital Ltd | Other services | 2025 |
| ATL Utilities Limited | Construction | 2006 |
| Atlantic Fibosh Ltd | Construction | 2025 |
| Atlantic Telecoms Services Group Limited | Information & communication | 2025 |
| Atlas 1834 Ltd | Professional & scientific | 2025 |
| Atlas Vehicle Transport Ltd | Transport & logistics | 2021 |
| Atomitz Limited | Information & communication | 2019 |
| Atoxor Limited | Professional & scientific | 2014 |
| Attenborough Financial Planning Ltd | Financial services | 2024 |
| AU Consultancy Surveyors Limited | Professional & scientific | 2023 |
| AU Property Portfolio Ltd | Real estate | 2014 |
| Audax Developments Ltd | Construction | 2020 |
| Audience Labs Ltd | Arts & recreation | 2022 |
| Audiojumble Limited | Administrative & support | 2015 |
| Audiora Ltd | Information & communication | 2025 |
| Audiostore Ltd | Manufacturing | 2017 |
| Audition Ready and Events and Education Ltd | Arts & recreation | 2024 |
| Audition Ready Limited | Arts & recreation | 2020 |
| Audrey's Fine Garment Care Ltd | Other services | 2025 |
| Audreys Laundry Ltd | Other services | 2020 |
| Augmene Limited | Information & communication | 2026 |
| Augustus Private Office Limited | Professional & scientific | 2023 |
| Auker Hutton Accountancy Limited | Professional & scientific | 2015 |
| Auker Hutton Legal Services Limited | Professional & scientific | 2019 |
| Auker Hutton Limited | Extraterritorial | 2019 |
| Auker Hutton Secretaries Limited | Administrative & support | 2015 |
| Aultmore Court Limited | Households | 1987 |
| Aultmore(Tunbridge Wells)Management Company Limited | Households | 2006 |
| Austen MAY Surveying Limited | Professional & scientific | 2023 |
| Austin Recruitment Consultants Limited | Administrative & support | 2008 |
| Austin Recruitment Limited | Administrative & support | 2017 |
| Australian Bodycare U.K. Limited | Wholesale & retail | 1989 |
| Autemetry Ltd | Information & communication | 2025 |
| Autohaus (IRE) Ltd | Wholesale & retail | 2009 |
| Automate Consulting Limited | Information & communication | 2014 |
| Automotive Initiative Ltd | Information & communication | 2021 |
| Autosport Customs Ltd | Wholesale & retail | 2019 |
| Autumn Financial Planning Limited | Financial services | 2023 |
| Autumna Limited | Health & social care | 2017 |
| AV Inspire Ltd | Construction | 2015 |
| AV Square Properties Ltd | Real estate | 2021 |
| AV Trinity Holdings Limited | Financial services | 2025 |
| AVA Global Logistics Limited | Professional & scientific | 2020 |
| Avama Video & Music Productions Limited | Arts & recreation | 2021 |
| Avantee Logistics Limited | Transport & logistics | 2014 |
| Avantif Ltd | Health & social care | 2025 |
| Aventus Interiors Limited | Construction | 2019 |
| Aviation Box Ltd | Information & communication | 2025 |
| Aviation Events Group Ltd | Administrative & support | 2019 |
| Avicenna Partnership Ltd. | Professional & scientific | 2003 |
| Avium Oculi Limited | Professional & scientific | 2024 |
| Avon Property Management Limited | Professional & scientific | 1993 |
| Avon Rosewell Limited | Information & communication | 2026 |
| Avonhead Business Services Ltd | Administrative & support | 2017 |
| Avoxy Technologies Limited | Information & communication | 2025 |
| AVT Group Holdings Ltd | Financial services | 2023 |
| AVT Professional Services Limited | Professional & scientific | 2026 |
| AVT Video Limited | Information & communication | 2023 |
| Avtq Assets Limited | Financial services | 2022 |
| Awaken Festival Ltd | Administrative & support | 2020 |
| Awesome Dog Limited | Information & communication | 2006 |
| Awesops Limited | Information & communication | 2018 |
| Awfully Greedy Limited | Information & communication | 2024 |
| Awsom Ltd | Extraterritorial | 2015 |
| Axel Mchugh Ltd | Professional & scientific | 2024 |
| Axemble Ltd | Professional & scientific | 2020 |
| Axios Technology Consulting Ltd | Information & communication | 2026 |
| Axon Associates Limited | Administrative & support | 2014 |
| Axor Consulting Ltd | Information & communication | 2013 |
| Aydazel Consulting Ltd | Professional & scientific | 2026 |
| AYS Systems Limited | Construction | 2020 |
| AZ Afghanistan Limited | Wholesale & retail | 2025 |
| AZA Power Ltd | Information & communication | 2018 |
| Azara Holdings Limited | Financial services | 2025 |
| Azara International Limited | Health & social care | 2025 |
| Azhagi Tantra Temple Ltd | Other services | 2021 |