| Auto Mend Centre Ltd | Wholesale & retail | 2023 |
| Auto Repairs GEN Ltd | Wholesale & retail | 2025 |
| Auto Rexhepi Ltd | Wholesale & retail | 2025 |
| Autocolour Limited | Wholesale & retail | 1981 |
| Autoelectrix Limited | Wholesale & retail | 2014 |
| Autolayer Ltd | Information & communication | 2025 |
| Autolycus House Ltd | Information & communication | 2012 |
| Automax Group Ltd | Wholesale & retail | 2018 |
| Automotiv Ltd | Wholesale & retail | 2022 |
| Automotive Cosmetic Excellence Limited | Wholesale & retail | 2018 |
| Autosdakar Limited | Wholesale & retail | 2019 |
| Autoworks Services Ltd | Wholesale & retail | 2018 |
| Autumn Creative Ltd | Professional & scientific | 2023 |
| Auxiliumplusuk Limited | Public administration | 2018 |
| AV Site Services Ltd | Construction | 2025 |
| AVA a K Ltd | Transport & logistics | 2026 |
| Avalon Court Management Company Limited | Households | 2002 |
| Avanta Consultancy and Training Ltd | Information & communication | 2025 |
| Avantra Ltd | Wholesale & retail | 2025 |
| Avazia Ltd | Information & communication | 2007 |
| Avebury House Management Limited | Households | 2015 |
| Aveer Enterprise Limited | Information & communication | 2023 |
| Aveer Property Management Limited | Real estate | 2024 |
| Avenel Court RTM Company Limited | Households | 2012 |
| Avenue Associates Limited | Professional & scientific | 2019 |
| Avglog Ltd | Transport & logistics | 2023 |
| Avia Car Wash Limited | Other services | 2016 |
| Aviation Engineering Training Ltd | Administrative & support | 2013 |
| Aviemore Holdings LP | | 2014 |
| Avieo Ltd | Wholesale & retail | 2026 |
| Avija Limited | Information & communication | 2008 |
| Aviqo Ltd | Wholesale & retail | 2026 |
| Avit Technical Services Limited | Information & communication | 2012 |
| AVL Construction and Home Services Ltd | Construction | 2022 |
| Avlisad Ltd | Real estate | 2025 |
| Avlon's Hair Studio Ltd | Other services | 2025 |
| Avmore Services Limited | | 1987 |
| Avonpark Ltd | Hospitality | 2019 |
| Avonpark Properties Limited | Real estate | 1996 |
| Avsys Limited | Information & communication | 1993 |
| Avtar Construction Limited | Construction | 2010 |
| AW Admin Services Limited | Real estate | 2023 |
| AW Creative Media Ltd | Professional & scientific | 2024 |
| Awacam Realty Ltd | Real estate | 2024 |
| Awake Deliveries Ltd | Transport & logistics | 2025 |
| Awakened Homes Ltd | Real estate | 2024 |
| Awan Practice Services Limited | Health & social care | 2007 |
| Away Space Limited | Real estate | 2015 |
| Awcustoms Limited | Wholesale & retail | 2021 |
| Awel Y MÔR Offshore Wind Farm Limited | Construction | 2019 |
| Aweng Care for U Ltd | Health & social care | 2025 |
| Aweswim Academy LLP | | 2025 |
| Axel Drylining Ltd | Construction | 2024 |
| Axelent Global Limited | Wholesale & retail | 2017 |
| Axelent Limited | Wholesale & retail | 2002 |
| Axford Property Limited | Real estate | 2021 |
| Axiom Minerals Ltd | Financial services | 2023 |
| Axion Local Ltd | Households | 2025 |
| Axis Football Investments Ltd | Arts & recreation | 2017 |
| Axis Maintenance Services UK Limited | Construction | 2006 |
| Axis Marketing Communications Limited | Professional & scientific | 1992 |
| Axis Property Partners Ltd | Real estate | 2025 |
| Axis Special Projects Limited | Construction | 2009 |
| Axis Sports Investment Ltd | Financial services | 2016 |
| Axonium Ltd | Information & communication | 2015 |
| Axxess Identification Limited | Manufacturing | 1993 |
| AY Realtors Limited | Real estate | 2022 |
| Ayakhe Holdings Ltd | Manufacturing | 2020 |
| Ayami Move Ltd | Transport & logistics | 2026 |
| Ayden & Veron Properties Ltd | Real estate | 2024 |
| Aydin Technologies Ltd | Information & communication | 2014 |
| Aydir Limited | Hospitality | 2023 |
| AYJ Limited | Information & communication | 2007 |
| Ayrton Design Ltd | Information & communication | 2026 |
| AZ Morgan Limited | Real estate | 2024 |
| Azelin Court RTM Company Limited | Households | 2006 |
| Aziel Care Ltd | Health & social care | 2026 |
| Azmat Traders Ltd | Wholesale & retail | 2025 |
| Azone Logistics Limited | Transport & logistics | 2008 |
| Azpm Limited | Manufacturing | 2014 |
| Aztec West Management Limited | Real estate | 1988 |
| B & B Gardening Limited | Hospitality | 2019 |
| B & K Trades Limited | Construction | 2017 |
| B & Z Painting Services Ltd | Construction | 2023 |
| B a Rescue Limited | Education | 2022 |
| B a Safety Ltd | Education | 2020 |
| B and M Trailers Ltd | Administrative & support | 2011 |
| B Brackets Ltd | Manufacturing | 2025 |
| B F Croscato Ltd | Transport & logistics | 2022 |
| B Gale Developments Ltd | Real estate | 2026 |
| B R O C Limited | Real estate | 1978 |
| B Reka Limited | Hospitality | 2025 |
| B W Properties (Swindon) Limited | Real estate | 2023 |
| B&B Prime Ltd | Wholesale & retail | 2021 |
| B&M Wells Ltd | Hospitality | 2025 |
| B&M(Grg) Limited | Transport & logistics | 2025 |
| B&N Property Ltd | Real estate | 2025 |
| B&O Homes Ltd | Real estate | 2023 |
| B&S Haulage Limited | Transport & logistics | 2026 |
| B&Z Draycott Ltd | Wholesale & retail | 2023 |