| Aubrac Cattle Society of the UK Limited | Salisbury | 1990 |
| Auchencheyne Limited | Thornhill | 1974 |
| Auchenforest Limited | Edinburgh | 1994 |
| Auchengate Carriage Driving Club Ltd | Irvine | 2021 |
| Auchenstarry Farm Limited | Glasgow | 1985 |
| Auchentoshan Limited | Glasgow | 2015 |
| Auchenvey Farm Ltd | Castle Douglas | 2025 |
| Auchineden Limited | Dunblane | 1991 |
| Auchlane Farming Company Limited | Castle Douglas | 2013 |
| Auchlishie Eventing Limited | Kirriemuir | 1999 |
| Auchlishie Livery Limited | Kirriemuir | 2008 |
| Auchmedden Farms Ltd | Peterhead | 2025 |
| Auchnabreac Limited | Campbeltown | 2025 |
| Auchnafree Estate Company | Notts | 1962 |
| Auchreoch ACF Limited | Glasgow | 2025 |
| Auckland Tree Services Ltd | Leyburn | 2018 |
| Aucuparia Farming Limited | Leeds | 2024 |
| Auditree Limited | Derby | 2024 |
| Audley END Farming Limited | Essex | 2018 |
| Audmaraid Ltd | Buckie | 2024 |
| Aughavarry Farms Limited | Ballymena | 2026 |
| Aughnahinch Farms Ltd | Newtownbutler | 2025 |
| Aughton PIG Producers Limited | Liverpool | 1991 |
| Augustus (Norfolk) Ltd | Norwich | 2020 |
| Aulaw Organic Farm UK C.I.C. | New Malden | 2022 |
| Auld Apple Tree Limited | Hamilton | 2024 |
| Auldmay K Elan Ltd | Beckenham | 2013 |
| Aulis R D Ltd | Cartmel | 2012 |
| Aunby Farming Limited | Stamford | 2025 |
| Aungier Livestock Limited | Bures | 2021 |
| Aunt Minnies Farm Ltd | Newry | 2023 |
| AUR Y Ddraig Ltd | Swansea | 2018 |
| Aurahigh Ltd | Irvine | 2025 |
| Auralis Botanics Ltd | Cardiff | 2025 |
| Aurasense Ltd | Manchester | 2019 |
| Aurelius Racing Limited | Wimborne | 2023 |
| Aurex Capital Group Ltd | Ruislip | 2025 |
| Aurora Barn Limited | Neath | 2025 |
| Aurora Charters Portrush Ltd | Ballymoney | 2025 |
| Aurora Farm Limited | Co. Londonderry | 1998 |
| Aurora Marine Ltd. | Shetland | 2011 |
| Aurora Marine Scotland Limited | Peterhead | 2019 |
| Aurora Nova Limited | Woodbridge | 2012 |
| Aurora Purr Ltd | Corby | 2026 |
| Aurora Shihtzu Ltd | Bury St. Edmunds | 2026 |
| Aurora Sustainability Ltd | Forres | 2016 |
| Aurora's Pets Best Care Limited | London | 2017 |
| Aurorabullyz Ltd | London | 2021 |
| Aurvandill Kennel & Livery Limited | Tonbridge | 2025 |
| Ausome Growsome CIC | Belfast | 2020 |
| Ausonia Nurseries Limited | Billericay | 1998 |
| Austeya Creative Group Ltd | Richmond | 2026 |
| Austin Enterprises Ltd | Market Harborough | 2021 |
| Austin Tree Care Ltd | Cambridge | 2020 |
| Austland Ltd | London | 2019 |
| Austons Down Limited | Warwickshire | 2004 |
| Auterstone Farm Limited | Penrith | 2025 |
| Autowin Ltd | London | 2025 |
| Autumn Engineering Limited | Kent | 1979 |
| Autumn Vines Limited | London | 2022 |
| AV & EPA Giordano Ltd | Presteigne | 2021 |
| AV Agri Ltd | Bewdley | 2022 |
| AV Equestrian Ltd | Strathaven | 2022 |
| AV Tree Surgeon Limited | London | 2023 |
| AVA Berries Limited | Evesham | 2025 |
| Avafarm Development Limited | London | 2021 |
| Avalon Bloodstock Ltd | Braintree | 2014 |
| Avalon Dogs Limited | Malton | 2022 |
| Avalon Venture Capital Limited | London | 2016 |
| Avantlu Ltd | Manchester | 2023 |
| Avantus Marketing Services UK Limited | Suffolk | 2023 |
| Avast Chef Group Ltd | London | 2025 |
| Avativ Ltd | Whitland | 2018 |
| Avcomm Developments Limited | London | 1981 |
| Aveland Pest Solutions Limited | Sleaford | 2010 |
| Aveland Trees Limited | Bourne Peterborough | 2004 |
| Aveley Allotment Association | Grays | 2025 |
| Avenger Ltd | London | 2026 |
| Avensgarth Ltd | Whalsay | 2011 |
| Avenue Farm Group Limited | Buckingham | 2025 |
| Avenue Farm Holdings Limited | Buckingham | 2025 |
| Avenue Farms Limited | London | 1967 |
| Averill Land Limited | Nottingham | 1999 |
| Averybay Limited | Sheffield | 1995 |
| Averys (Radnage) Limited | Spilsby | 1938 |
| Avexiabiotec Limited | Birmingham | 2019 |
| Aviacon Ltd | London | 2020 |
| Aviadale Limited | London | 1983 |
| Aviagen International Finance Five Limited | Stratford Upon Avon | 2009 |
| Aviagen Limited | Stratford-Upon-Avon | 1982 |
| Aviagen Turkeys Limited | Tattenhall | 1962 |
| Aviagen UK Limited | Newbridge | 1978 |
| Avian Breeding Limited | Doncaster | 2018 |
| Avian ID Limited | Redruth | 2026 |
| Aviary Farm Ltd | Ellesmere Port | 2025 |
| Aviatica Bloodstock Limited | Cambridge | 2020 |
| Avifarm Services Ltd | Carlisle | 2025 |
| Aviguard Network Limited | Redditch | 2026 |
| Avis Agri Ltd | Taunton | 2026 |
| Avivets Veterinary Services Ltd | Pickmere | 2025 |