| Castles Property Sales FS Ltd | Hemel Hempstead | 2024 |
| Castleshane Investments Limited | Belfast | 2018 |
| Castleshouse Holdings Ltd | Dronfield | 2025 |
| Castlestone Holdings Limited | Barnsley | 2017 |
| Castlestone Specialist Property Finance Ltd | Hemel Hempstead | 2024 |
| Castletech Construction (Holdings) Limited | Poole | 2013 |
| Castleton Properties (Leeds) Ltd. | Wetherby | 2019 |
| Castleton Ventures Limited | Swanscombe | 2026 |
| Castletown Holdings Limited | Scunthorpe | 2020 |
| Castletown Limited | Watford | 2005 |
| Castleview Group Holdings Limited | Chester Le Street | 2022 |
| Castleview Holdings (N.I.) Ltd | Belfast | 2020 |
| Castlevine Limited | London | 2023 |
| Castlewall Limited | Kent | 1992 |
| Castlewell Capital Ltd | Glasgow | 2026 |
| Castlewood Holdco Limited | Borehamwood | 2019 |
| Castleworth Investments Ltd | Middlesbrough | 2022 |
| Castor Financing Limited | London | 2023 |
| Castor Holdings Limited | London | 2023 |
| Castor Investments Limited | London | 2021 |
| Castor Management Limited | Cambs | 2005 |
| Castori Properties Ltd | Egham | 2020 |
| Castra Estate Planning Limited | Cwmbran | 2021 |
| Castra Financial Limited | Cwmbran | 2019 |
| Castrafeld Management Limited | Haywards Heath | 2023 |
| Castramet Holdings Limited | Stalybridge | 2023 |
| Castrius Capital Partners Limited | Newcastle Upon Tyne | 2025 |
| Castrius Investment Holdings Limited | Newcastle Upon Tyne | 2025 |
| Castrius Venture Accelerator Limited | Newcastle Upon Tyne | 2025 |
| Castro Ltd | London | 2011 |
| CASTRO17 Ltd | London | 2025 |
| Castrol Holdings Americas Limited | Middlesex | 2020 |
| Castrol Holdings International Limited | Middlesex | 2020 |
| Castrostead Ltd | Hereford | 2024 |
| Castrum PAY Ltd | London | 2023 |
| Casual Investments Limited | London | 2021 |
| Casually EN Route Ltd | London | 2018 |
| Casus Group Limited | Leeds | 2019 |
| Casus Underwriting Limited | Rochford | 2023 |
| Caswick Holdings Limited | Doncaster | 2020 |
| Cat and ELA Properties Ltd | Northampton | 2017 |
| Cat Ballou Holdings Limited | Coventry | 2023 |
| Cat Capital Holdings Ltd | Chandlers Ford | 2019 |
| Cat Capital Limited | London | 2018 |
| Cat Holdings Ltd | Shepton Mallet | 2022 |
| Cat Holdings Somerset Ltd | Somerton | 2026 |
| Cat Trading Group Limited | Leytonstone | 2014 |
| Cat Tree Group Limited | London | 2018 |
| CAT6 Limited | Glasgow | 2024 |
| Cata Holdings Ltd | Tamworth | 2026 |
| Catalco Holdings Ltd | Widnes | 2019 |
| Catalent CTS UK Holding Limited | Swindon | 2012 |
| Catalina Echo Limited | Worthing | 2010 |
| Catalina Growth Partners Ltd | London | 2026 |
| Catalina Holdings UK Limited | Worthing | 1999 |
| Catalina Investments Limited | Hoddesdon | 2016 |
| Catalina Worthing Insurance Limited | Worthing | 2006 |
| Catalio Capital UK Ltd. | Altrincham | 2021 |
| Catalpa Financial Planning Ltd | Brentwood | 2013 |
| Catalpa Investments Limited | Bedford | 2019 |
| Catalpa Limited | Brentwood | 2013 |
| Catalyse Capital Holdings Limited | York | 2022 |
| Catalysis Capital Partners Limited | Caterham | 2004 |
| Catalyst Acquisitions Group Ltd | Hull | 2024 |
| Catalyst Asset Finance Limited | Totton, Southampton | 2026 |
| Catalyst at Large Limited | Bristol | 2011 |
| Catalyst Branding Group Ltd | Birmingham | 2025 |
| Catalyst Business Finance Limited | London | 2012 |
| Catalyst Care Group Ltd | Bristol | 2011 |
| Catalyst CCG Limited | Bristol | 2023 |
| Catalyst DMS UK Ltd | Harrow | 2024 |
| Catalyst Energy Storage Platform Limited | London | 2021 |
| Catalyst EPF (Scots) GP Limited | Edinburgh | 2008 |
| Catalyst Finance Limited | Southampton | 2022 |
| Catalyst Global Group Ltd | London | 2025 |
| Catalyst Group Services Ltd | Northampton | 2023 |
| Catalyst Holdings Limited | York | 2019 |
| Catalyst Impact Investment Club Limited | London | 2023 |
| Catalyst Infra Ltd. | London | 2013 |
| Catalyst Media Holdings Limited | London | 2005 |
| Catalyst Midco Limited | London | 2025 |
| Catalyst Newco 3 Limited | London | 2018 |
| Catalyst Otis Limited | Manchester | 2003 |
| Catalyst PIM Limited | London | 2025 |
| Catalyst Quail Limited | Manchester | 2001 |
| Catalyst Services UK Ltd | Oldham | 2014 |
| Catalyst Solutions Financial Limited | London | 2023 |
| Catalyst Therapy Ltd. | London | 2014 |
| Catalyst Topco Limited | London | 2025 |
| Catalyst Trading Systems Ltd | Wantage | 2025 |
| Catalyst Tulip Bidco Limited | Doncaster | 2022 |
| Catalyst Tulip Midco Limited | Doncaster | 2022 |
| Catalystfm (UK) Limited | London | 2025 |
| Catalyte Ltd | London | 2025 |
| Catalytic Capital Ltd | Edinburgh | 2026 |
| Catalyx Partners Ltd | Horsham | 2026 |
| Catalyza Group Ltd | Luton | 2026 |
| Catam Limited | Wilmslow | 2018 |
| Catamarano Ltd | London | 2026 |
| Catana Holdings Limited | Ellesmere Port | 2025 |