| ATH Ventures Ltd | London | 2026 |
| Atha Group Holdings Limited | Middlesbrough | 2023 |
| Athag Holdings Ltd | Atherstone | 2023 |
| Athagoras Aquico UK-01 Limited | Wantage | 2024 |
| Athalie Limited | London | 2018 |
| Athamus Holdings Limited | London | 2021 |
| Athanor Corporation Ltd | Bourne End | 2025 |
| Athanor Limited | London | 1993 |
| Atharus Ltd | Sutton | 2018 |
| Atharv Finance Ltd | Uxbridge | 2025 |
| Atheia Capital Limited | London | 2026 |
| Athelis Financial Ltd | Warrington | 2018 |
| Athelmead Ltd | Dornoch | 2026 |
| Athelney Developments Limited | Eastleigh | 2024 |
| Athelney Group Ltd | Woodstock | 2024 |
| Athelney Trust PLC | Penryn | 1994 |
| Athena and Soteria Limited | Norwich | 2025 |
| Athena ATE Limited | Blackburn | 2024 |
| Athena Autos Limited | Dereham | 2017 |
| Athena Business Ltd | London | 2023 |
| Athena Consillium Ltd | Ashford | 2013 |
| Athena Dhir Holdings Ltd | Dartford | 2017 |
| Athena Enterprises (UK) Limited | Stevenage | 2008 |
| Athena Equities Ltd | London | 2013 |
| Athena Family Investments | Warwick | 2024 |
| Athena Fiduciaries Limited | Stourbridge | 2014 |
| Athena Fiduciary Management Limited | Stourbridge | 2018 |
| Athena Finance Solutions Ltd | Tamworth | 2024 |
| Athena Financial Planning Limited | Worcester | 2007 |
| Athena Holdco Limited | Poole | 2019 |
| Athena Holdings Group Limited | Birmingham | 2024 |
| Athena IFA Ltd | Esher | 2023 |
| Athena Industries Limited | London | 2021 |
| Athena Infinite Spirit Ltd | Guildford | 2018 |
| Athena Insurance Services Limited | Nuneaton | 1992 |
| Athena Midco Limited | Brighton | 2023 |
| Athena Mortgages Limited | Glasgow | 2017 |
| Athena Partners Ltd | London | 2018 |
| Athena Portfolio Limited | London | 2015 |
| Athena RE (UK) Limited | London | 2025 |
| Athena REI Ltd | Sutton Coldfield | 2021 |
| Athena Sports Group Ltd | Poole | 2025 |
| Athena Topco Limited | Brighton | 2023 |
| Athena UK Holdco Limited | Brighton | 2023 |
| Athena UK Holdings Ltd | London | 2021 |
| Athena Underwriting (904) Limited | London | 2004 |
| Athena Venture Capital Limited | Sheffield | 2022 |
| Athena Wealth Ltd | Blackburn | 2016 |
| Athena XI Property Group Ltd | Glasgow | 2025 |
| Athenad Holdings Limited | Southampton | 2022 |
| Athene Praxis Ltd | London | 2025 |
| Athene Ventures Limited | Gloucester | 2021 |
| Atheneum AI Holdings Ltd | Torquay | 2026 |
| Atheneys Law Limited | Ringwood | 2018 |
| Athenion Holdings Limited | Manchester | 2025 |
| Athens Consulting Limited | Rickmansworth | 2016 |
| Athens Value Creation Consultancy Limited | Warrington | 2025 |
| Athercap Limited | London | 2024 |
| Atherden Fuller Leng (Holdings) Limited | Manchester | 2022 |
| Atherion Energy Limited | London | 2025 |
| Atherion Holdings Limited | London | 2025 |
| Athers Investments Limited | Chelmsford | 2019 |
| Atherton and Associates Wealth Management Ltd | Nantwich | 2020 |
| Atherton and Associates Wealth Management Nantwich Ltd | Nantwich | 2009 |
| Atherton Consultancy (North West) Ltd | Bolton | 2011 |
| Atherton Financial Consultancy Limited | Manchester | 2013 |
| Atherton Holdings Limited | Retford | 2015 |
| Atherton Media Group Limited | Warwick | 2025 |
| Atherton York Group Limited | Barnet | 2020 |
| Atherton York Limited | Barnet | 2013 |
| Athica Limited | Surrey | 2016 |
| Athins Accountants Ltd | London | 2021 |
| Athirt Limited | Poole | 2021 |
| Athla Capital Management Limited | Radstock | 2018 |
| Athlete Inc Limited | Norwich | 2024 |
| Athlete PI Holdings Ltd | Ipswich | 2024 |
| Athletic Enterprises Limited | London | 2020 |
| Athletics Data Limited | London | 2003 |
| Athlon Mobility Services UK Limited | Milton Keynes | 1998 |
| Athlon Real Estate Limited | Whitehills Business Park | 2009 |
| Athlone Healthcare Group Limited | Dartford | 2008 |
| Athlone Holding Company Ltd. | Dundee | 2016 |
| Athol Street Holdings Limited | Preston | 2025 |
| Atholl Crescent Propco Limited | London | 2024 |
| Atholl Scott Financial Services Limited | Aberdeen | 1988 |
| Athora UK Holding Limited | London | 2025 |
| Athos Capital (UK) Limited | London | 2026 |
| Athos Commercial Finance Limited | Gateshead | 2026 |
| Athos Development Services Ltd | Peterborough | 2020 |
| Athw Holdings Limited | Tewkesbury | 2025 |
| Athwal Holdings Limited | Wolverhampton | 2008 |
| Athyrium Opportunities IV UK Qahc Ltd | London | 2022 |
| ATI Holdings Limited | Alton | 2020 |
| ATI UK Holdings Ltd | Woking | 2021 |
| Atia R&I Limited | Leicester | 2023 |
| Atid Holdings Ltd | London | 2020 |
| Atif Group Ltd | Manchester | 2024 |
| Atika Group Holdings Ltd | Warrington | 2025 |
| Atila Ltd | London | 2025 |
| Atino Group Limited | Warrington | 2024 |