| Athena Print Management Limited | Watford | 2018 |
| Athena Welding Ltd | Swanage | 2015 |
| Athena Worksurface Fabrications Ltd | Droitwich | 2014 |
| Athenaeum Press Limited | Newcastle Upon Tyne | 1986 |
| Athenaguard Ltd | Glasgow | 2025 |
| Athenas Sports Ltd | Craigavon | 2021 |
| Athene Shipping Limited | London | 2020 |
| Athenian Bakery Ltd | Cockfosters | 2022 |
| Athenova Consult Ltd. | Waterlooville | 2020 |
| Atherley Limited | Sheffield | 2023 |
| Atherstone Industrial Coatings Limited | Arley | 1979 |
| Atherton Bikes Limited | Oswestry | 2018 |
| Atherton Conveyor Spares Limited | Retford | 2019 |
| Atherton Creative Engineering Services Ltd | Northwich | 2023 |
| Atherton Engineering Limited | | 2001 |
| Atherton Materials Handling Limited | Retford | 2009 |
| Atherton Plant Services Limited | Runcorn | 2021 |
| Athertones Ltd | London | 2021 |
| Athim Studios Ltd | London | 2025 |
| Athingofbeauti Ltd | Enfield | 2018 |
| Athion Labs Ltd | Dumbarton | 2022 |
| Athiri Group Limited | Milton Keynes | 2012 |
| Athlegend Limited | London | 2010 |
| Athlete Journey Ltd | London | 2025 |
| Athletes Best Source Ltd | Wellingborough | 2023 |
| Athletic Boost Ltd | Birmingham | 2018 |
| Athletic Brewing Co. UK Limited | London | 2021 |
| Athletic Company Limited | Hounslow | 2021 |
| Athletic Installations Ltd | Leicester | 2023 |
| Athletic Technology Company Limited | Oxford | 2019 |
| Athleticoapparel Ltd | Wembley | 2024 |
| Athlion Sports Ltd | Heywood | 2025 |
| Athlomax Limited | London | 2024 |
| Athlé Ltd | Washington | 2025 |
| Athol Paints Bury Limited | Bury | 2026 |
| Athol Paints Limited | Bury | 1976 |
| Atholl Industrial Solutions Limited | Glasgow | 2017 |
| ATHOLLCO10 Limited | Edinburgh | 2024 |
| Athom Design Limited | Chippenham | 2003 |
| Athwear Limited | Broadstairs | 2018 |
| ATI Electrical Ltd. | Gloucester | 2021 |
| ATI Environment UK Limited | London | 2010 |
| Ati-Industrie Ltd | Manchester | 2013 |
| Atia Beauty Care Limited | Hounslow | 2023 |
| Atico Limited | Hampshire | 2006 |
| Atif Antiques Ltd | London | 2025 |
| Atiframai Limited | High Wycombe | 2011 |
| Atik 3D Ltd | Brentwood | 2025 |
| Atik Cameras Limited | Cambridge | 2006 |
| Atikoo Ltd | London | 2025 |
| Atilade Busari Foundation CIC | London | 2025 |
| Atilla Composites Ltd | Cambridge | 2026 |
| Atincola Ltd | Croydon | 2026 |
| Atinga UK Productions Limited | Liverpool | 2022 |
| Atitlan Studios Ltd | Fareham | 2020 |
| Ative Project Ltd | Marlow | 2026 |
| Atiyukt Aroma Ltd | Watford | 2025 |
| ATJ Inspect Ltd | Purfleet | 2021 |
| ATJ Rowfant Vehicle Inspection Centre Ltd | Crawley | 2026 |
| Atjb Services Limited | Nottingham | 2022 |
| ATK Composites Ltd | Cambridge | 2024 |
| Atken Limited | Wetherby | 2023 |
| Atkey and Company Limited | Clevedon | 2009 |
| Atkhennie's Essentials Limited | London | 2025 |
| Atkin Guitars Limited | Canterbury | 2019 |
| Atkin Machine Tool Maintenance Ltd | Heywood | 2002 |
| Atkin, Grant and Lang Limited | Witney | 1984 |
| Atkins & Downie | Firbeck Worksop | 1984 |
| Atkins and Potts Limited | Newbury | 2004 |
| Atkins Marine Services Ltd | Weston-Super-Mare | 2022 |
| Atkinson & Kirby Limited | Wrexham | 1926 |
| Atkinson Aero Services Ltd | Southend-On-Sea | 2025 |
| Atkinson Bookbinders Limited | Salisbury | 2005 |
| Atkinson Building & Carpentry Ltd | Hereford | 2023 |
| Atkinson Developments Limited | Kington | 2016 |
| Atkinson Family Wines Limited | Milton Keynes | 2022 |
| Atkinson Plant Services Ltd | Middlesbrough | 2025 |
| Atkinson Technical Group Limited | Hyde | 2000 |
| Atkinson Wines Ltd | Derby | 2017 |
| Atkinsons Fencing and Decking Centres Limited | Castleford | 2004 |
| Atkinsons Fencing Limited | Castleford, | 1993 |
| Atkinsons Home and Garden Limited | Castleford | 2022 |
| Atkinsons Joiners Limited | Co Durham | 2005 |
| Atkinsons of Manchester Ltd | Burnley | 2024 |
| Atkinsons Traditional Joinery Ltd | Blackpool | 2017 |
| Atkinz Consult Ltd | London | 2017 |
| Atkon Innovation UK Ltd | London | 2024 |
| ATL Aviation Ltd | Ipswich | 2020 |
| ATL Components Limited | Haddenham | 2020 |
| ATL Garage Services Ltd | Liphook | 2005 |
| ATL Group Ltd | London | 2020 |
| ATL Packaging Limited | Coventry | 2006 |
| ATL Precision Engineering Ltd | Gateshead | 2015 |
| ATL Product Sales Limited | Haddenham | 2024 |
| ATL Renewables Ltd | Guisborough | 2022 |
| ATL Transformers Limited | Middleton | 1981 |
| Atla Projects Ltd | Manchester | 2025 |
| Atlant 3D Limited | London | 2021 |
| Atlant Capital Group Ltd | Grays | 2022 |
| Atlanta (UK) Limited | Dudley | 1989 |