| APK Engineering Services Limited | Professional & scientific | 2021 |
| Apple PIE Limited | Professional & scientific | 1996 |
| Applewick Dairy Limited | Agriculture & fishing | 2012 |
| Apprentice First Ltd | Education | 2024 |
| Approved Business Advisers Ltd | Professional & scientific | 2026 |
| Apre Surfacing Limited | Construction | 2001 |
| April Property Services Ltd | Real estate | 2025 |
| APS Advisory Ltd | Professional & scientific | 2022 |
| APT Ledger Ltd | Information & communication | 2024 |
| AQ Holdings (Southwest) Limited | Real estate | 2024 |
| Aquaplanet Limited | Wholesale & retail | 2020 |
| Aquetong Farming Limited | Agriculture & fishing | 2003 |
| Aquila IT Ltd | Information & communication | 2015 |
| Aquitaine Property Investments Ltd | Real estate | 2025 |
| Aradab Ltd | Real estate | 2025 |
| ARC Airstreams Limited | Extraterritorial | 2013 |
| Archaeological Surveys Limited | Administrative & support | 2007 |
| Architectural Oak Limited | Manufacturing | 2004 |
| Ardella Business Consulting Ltd | Professional & scientific | 2025 |
| Ardour Consulting Limited | Professional & scientific | 2014 |
| Aretousa Ltd | Education | 2024 |
| Aristone Management Limited | Households | 2025 |
| Arketik Technology Services Limited | Information & communication | 2022 |
| Arms Farm LLP | | 2014 |
| Armstrong Architecture Limited | Professional & scientific | 2019 |
| Armstrong's Hairdressing & Barbering Ltd | Other services | 2023 |
| ARS Mercatus Ltd | Professional & scientific | 2025 |
| Ars-Patent LLP | | 2018 |
| Ars-Patent UK Ltd | Professional & scientific | 2019 |
| Artech Ventures Ltd | Information & communication | 2025 |
| ARTEL31 Limited | Construction | 2003 |
| Artground Limited | Arts & recreation | 2021 |
| Artificial Synthetic Intelligence Ltd | Information & communication | 2024 |
| Artisan Biscuits Limited | Manufacturing | 1973 |
| Artstream Media Ltd | Arts & recreation | 2019 |
| Arvonia Veterinary Limited | Professional & scientific | 2007 |
| Ascari Training & Consulting Ltd | Professional & scientific | 1998 |
| ASH Group Consulting (Uk&I) Limited | Professional & scientific | 2026 |
| Ashayes Limited | Real estate | 1996 |
| Ashcroft Property Limited | Real estate | 2021 |
| Asher Broomfield Limited | Professional & scientific | 2012 |
| Ashwicke Consulting Ltd | Professional & scientific | 2023 |
| Ashwicke Hall School Limited | Education | 1983 |
| ASK Adam Tech Ltd | Information & communication | 2026 |
| Asleep Ltd | Real estate | 2019 |
| Asna Consulting Limited | Information & communication | 2023 |
| Aspen Estate Management Ltd | Professional & scientific | 2024 |
| Aspire Commercial Finance Limited | Financial services | 2014 |
| Aspire Property Finance Limited | Financial services | 2021 |
| Astute Architecture & Technology Ltd | Information & communication | 2012 |
| Astute Business Compliance Limited | Professional & scientific | 2016 |
| Astutely Ltd | Information & communication | 2013 |
| Asystsu Trustees Limited | Administrative & support | 2023 |
| Atentu Ltd | Professional & scientific | 2020 |
| Athelstan Services Ltd | Information & communication | 2023 |
| Athom Design Limited | Manufacturing | 2003 |
| Atkinson & OOI Ltd | Health & social care | 2017 |
| Atlantis AV Solutions Ltd | Other services | 2002 |
| ATP Health & Fitness Ltd | Arts & recreation | 2009 |
| ATS Digital Solutions Limited | Manufacturing | 2023 |
| Attention Deficit Hospitality Disorder Ltd | Professional & scientific | 2025 |
| Atwood Ventures Limited | Information & communication | 2020 |
| Auditing Solutions Limited | Professional & scientific | 2002 |
| Aurora Dental Clinic Chippenham Limited | Health & social care | 2020 |
| Aurvea Ltd | Information & communication | 2025 |
| Ausculta Ltd | Information & communication | 2014 |
| Austinmusic Limited | Information & communication | 2013 |
| Auto Atelier Ltd | Transport & logistics | 2025 |
| Autojones Mobile Mechanic Ltd | Wholesale & retail | 2024 |
| Automation Sales Limited | Manufacturing | 2001 |
| Autosim Engineering Ltd | Professional & scientific | 2012 |
| Auxiliumn Associates Ltd | Professional & scientific | 2018 |
| Avant Art Tattoo Ltd | Arts & recreation | 2017 |
| Avent Builders Limited | Construction | 2019 |
| Avent Vouchers Ltd | Administrative & support | 2009 |
| Avenue LE Fleche Management Ltd | Households | 2023 |
| Aviascia Limited | Administrative & support | 2023 |
| Avieella Ltd | Financial services | 2024 |
| Avils Consulting Limited | Professional & scientific | 2009 |
| Aviv Coaching Ltd | Education | 2022 |
| Avon Engineering Services Limited | Manufacturing | 2016 |
| Avon Marine Services Limited | Manufacturing | 2024 |
| Avon Meadows (NO.1) Management Company Limited | Administrative & support | 1990 |
| Avon Reach (Chippenham) Management Limited | Households | 1987 |
| Avon School of Journalism Limited | Education | 1920 |
| Avon Storage Solutions Limited | Transport & logistics | 2014 |
| Avon Surgical Limited | Extraterritorial | 2017 |
| Avon Valley Cleaning & Restoration Limited | Other services | 2010 |
| Avondale Garage Management Company Ltd | Households | 2026 |
| Avonweir Services Limited | Construction | 2011 |
| Awdry House Management Company Limited | Households | 2015 |
| Axcess Health Limited | Public administration | 2024 |
| AXE Private Equity Limited | Professional & scientific | 2014 |
| Axiah Ltd | Professional & scientific | 2014 |
| Axle Training Services Limited | Education | 2016 |
| Ayla Investments Ltd | Real estate | 2020 |
| Aylesbury Logistics Limited | Transport & logistics | 2006 |
| Azuli International Limited | Professional & scientific | 2023 |
| Azuli Ltd | Professional & scientific | 2022 |
| Azura One Limited | Information & communication | 2020 |