| Atalaya Investments Limited | Westcliff-On-Sea | 2017 |
| Atalaya Midco UK Limited | London | 2023 |
| Ataline Advisers Limited | Beaconsfield | 2024 |
| Atanash Ltd | Stockton-On-Tees | 2022 |
| Atao Solutions Limited | London | 2023 |
| Atara Holdings Ltd | Horsham | 2025 |
| Ataraxia 10 Limited | Maidstone | 2021 |
| Ataraxia 11 Limited | Maidstone | 2021 |
| Ataraxia 12 Limited | Maidstone | 2021 |
| Ataraxia 13 Limited | Maidstone | 2022 |
| Ataraxia 14 Limited | Maidstone | 2022 |
| Ataraxia 15 Limited | Maidstone | 2022 |
| Ataraxia 16 Limited | Maidstone | 2023 |
| Ataraxia 17 Limited | Maidstone | 2023 |
| Ataraxia 18 Limited | Maidstone | 2023 |
| Ataraxia 2 Limited | Stoke-On-Trent | 2018 |
| Ataraxia 4 Ltd | Maidstone | 2019 |
| Ataraxia 5 Limited | Maidstone | 2019 |
| Ataraxia 6 Ltd | Maidstone | 2019 |
| Ataraxia 7 Limited | Maidstone | 2021 |
| Ataraxia 8 Limited | Maidstone | 2021 |
| Ataraxia 9 Limited | Maidstone | 2021 |
| Ataraxia Broking Ltd | Maidstone | 2010 |
| Ataraxia Dixons Ltd | Maidstone | 2018 |
| Ataraxia Trade Ltd | London | 2025 |
| Atargis Energy UK Limited | Edinburgh | 2025 |
| Atariya-Ishimitsu UK Ltd | Hove | 2023 |
| Atasure Ltd | London | 2025 |
| Atat Ansah Group Limited | Milton Keynes | 2024 |
| Atavus Alliance Capital Ltd | London | 2026 |
| Atay Holding Limited | Halstead | 2024 |
| ATB 2021 Bidco Limited | St. Leonards-On-Sea | 2021 |
| ATB 2021 Midco Limited | St. Leonards-On-Sea | 2021 |
| ATB 2021 Topco Limited | St. Leonards-On-Sea | 2021 |
| ATB Group Holdings Ltd | Orpington | 2025 |
| ATB Holdings and Investments Ltd | Nuneaton | 2024 |
| ATB Merchant Limited | London | 2021 |
| Atbsl Ltd | London | 2025 |
| ATC Capital Partners Ltd | London | 2022 |
| ATC Events Ltd | London | 2023 |
| ATC Experience Ltd | London | 2022 |
| ATC Holdings Group Limited | Newcastle | 2026 |
| ATC Investments Holdings Limited | London | 2026 |
| ATC Representation Ltd | London | 2023 |
| ATC Rights Ltd | London | 2023 |
| ATC Sipro Ltd | Northampton | 2017 |
| Atce Group Limited | Tamworth | 2023 |
| Atcf UK Limited | London | 2021 |
| Atcg Holdings Ltd | London | 2026 |
| Atco Investments Limited | Rotherham | 2024 |
| Atco Money Exchange Ltd. | Ilford | 2005 |
| Atcp Investments Ltd | Marlow | 2024 |
| Atcs Holdings Limited | Scunthorpe | 2024 |
| ATD Business Ltd | Worcester | 2019 |
| ATD Group Holdings Limited | Hoddesdon | 2022 |
| ATD Trade & Holding Ltd | Hemel Hempstead | 2025 |
| ATE Global Ltd | Colchester | 2016 |
| ATE O'Clock Limited | York | 2021 |
| ATE Property Holdings Ltd | Poole | 2026 |
| Atec Group (Holdco) Limited | Chipping Norton | 2017 |
| Atec Group (Midco) Limited | Chipping Norton | 2017 |
| Atec Group Holdings Limited | Chipping Norton | 2017 |
| Atec Group Limited | Chipping Norton | 2017 |
| Atech Group Limited | London | 2022 |
| Atech Holdco Limited | London | 2022 |
| Atech Holdings Limited | Windsor | 2025 |
| Ateeg Investments | Leicester | 2025 |
| Atel Holdings Limited | Peterlee | 2019 |
| Atelier & Grove Ltd | London | 2025 |
| Atelier Capital Partners Limited | London | 2019 |
| Atelier Chelsea Holdings Ltd | Glovers End | 2025 |
| Atelier Design Holdings Ltd | Bridgnorth | 2025 |
| Atelier Group Holdings Limited | Macclesfield | 2019 |
| Atelier Investments Ltd | London | 2019 |
| Atelier Khan Group Ltd | London | 2025 |
| Atelier Saba Holdings Ltd | Ilford | 2026 |
| Atelier Wealth Ltd | Liverpool | 2023 |
| Atelier Winchester Limited | Winchester | 2026 |
| Atell Holdings Ltd | London | 2024 |
| Atem Holding Limited | London | 2025 |
| Atempo Growth II Advisory Limited | London | 2024 |
| Aten Europe Limited | Maidenhead | 2006 |
| Atena Care Slupsk Ltd | London | 2026 |
| Atena Holding Ltd | South Yorkshire | 2025 |
| Atenas Financial Services Limited | Liverpool | 2024 |
| Aternia Capital Partners Limited | Chigwell | 2026 |
| Aterrima Holdings Limited | London | 1972 |
| Atesh Holdings Limited | London | 2026 |
| Atet Holdings Ltd | Glasgow | 2025 |
| ATF Commercial Limited | Harleston | 1999 |
| ATF Finance Ltd | Milton Keynes | 2014 |
| ATF Participation Ltd | London | 2023 |
| ATF SW Holdings Ltd | Yeovil | 2020 |
| Atfi Limited | Oldbury | 2018 |
| ATG Claims Ltd | Glasgow | 2023 |
| ATG Investments UK Limited | Beaconsfield | 2017 |
| ATG US Holdings Limited | London | 2023 |
| Atg-Uk Parent Limited | London | 2023 |
| Atgc Group Ltd | London | 2025 |
| ATH Property Ltd | London | 2024 |