| Castleford Management Limited | Castleford | 2019 |
| Castleford Physiotherapy Limited | Castleford | 2020 |
| Castlegate (Psychologists) International Limited | London | 2011 |
| Castlegate Cutz Ltd | Knaresborough | 2025 |
| Castlegate Marine Club Limited | Stockton-On-Tees | 2000 |
| Castlegate Nursery & OUT of School Club Limited | Kelso | 2019 |
| Castlehaven Private Limited | London | 2017 |
| Castlekeep Safety Ltd | Milton Keynes | 2024 |
| Castleman & Dean Network Ltd | Burgess Hill | 2010 |
| Castleman Cattery Ltd | Reading | 2001 |
| Castlemead Management Limited | Rayleigh | 1994 |
| Castlemeare Ltd | Hollinwood | 2022 |
| Castlemind Coaching Ltd | Dundee | 2023 |
| Castlemount Limited | Towcester | 1987 |
| Castlequarter Coaching Limited | Holywood | 2014 |
| Castlereagh Office Management Limited | Belfast | 2004 |
| Castlerock Community Association | Coleraine | 2011 |
| Castlet EOT Limited | Lincoln | 2025 |
| Castletech Projects Ltd | Poole | 2015 |
| Castlethorn Limited | London | 2022 |
| Castlethorpe Investments Limited | Stonesby | 2004 |
| Castleton Events Ltd | Alloa | 2022 |
| Castleton Park Limited | Staverton | 2023 |
| Castletons Independent Family Funeral Services Limited | Rochdale | 2025 |
| Castleuk Ltd | Hinckley | 2012 |
| Castleview Storage Ltd | Worthing | 2018 |
| Castleville Developments Limited | | 1977 |
| Castleway Corporation Limited | Tunbridge Wells, Kent | 2017 |
| Castleway Management Limited | Cambridge | 2017 |
| Castleway Services Limited | Tunbridge Wells, Kent | 2018 |
| Castlewellan Regeneration Limited | Castlewellan | 1993 |
| Castlewood Hair Ltd | Dundee | 2025 |
| Castlewood Land & Development Limited | Birkenhead | 2025 |
| Castoman Limited | Sale | 2024 |
| Castor & Ailsworth Village Hall Limited | Peterborough | 2016 |
| Castor Consultancy Ltd | London | 2020 |
| Castor Research Limited | Reading | 2022 |
| Castor Resources Ltd | Worcester | 2024 |
| Castra Services Limited | Southampton | 2015 |
| Castrads Limited | Stockport | 2011 |
| Castrelle Ltd | London | 2023 |
| Castro Catering Equipment Ltd | Shrewsbury | 2019 |
| Castro's Barbershop Limited | London | 2025 |
| Castugans Ltd | London | 2025 |
| Casual Ballerz CIC | Basingstoke | 2017 |
| Casuite Ltd | Hastings | 2025 |
| Cat Action Trust Shops Limited | Croydon | 2013 |
| Cat Costa Aesthetics Limited | Coatbridge | 2020 |
| Cat Crawford Limited | London | 2013 |
| Cat Groomers UK Limited | London | 2026 |
| Cat Hill Equine Water Treadmill Ltd | Sheffield | 2022 |
| Cat III London Limited | Luton | 2013 |
| Cat in a Flat Limited | London | 2014 |
| Cat Jane Fitness Ltd | Colwyn Bay | 2022 |
| Cat Jemmy Nutrition & Fitness Limited | Belfast | 2024 |
| Cat Limited | Leeds | 1995 |
| Cat Music Limited | London | 1966 |
| Cat Scotland Ltd | Edinburgh | 2020 |
| Cat Services Ltd | Ashford | 2016 |
| Cat Sitter SW17 Ltd | London | 2015 |
| Cat Sitters UK Limited | London | 2026 |
| Cat Values Scotland Ltd | Glasgow | 2019 |
| Cata Security Ltd | London | 2020 |
| Catachem Solutions Limited | Malvern | 2012 |
| Catalan Paradise Limited | London | 2024 |
| Cataleia Company Ltd | Maidenhead | 2024 |
| Cataleya Beauty Ltd | Newport | 2019 |
| Cataleya Solutions Ltd | Preston | 2023 |
| Catalin Baicu Driving Ltd | Coventry | 2017 |
| Catalin Hodorogea Limited | Slough | 2018 |
| Catalin Niculescu Ltd | Birmingham | 2018 |
| Catalina Saft Consulting Ltd | Ruislip | 2018 |
| Catalis Holdings Limited | London | 2019 |
| Catalis Limited | East Croydon | 2018 |
| Catalisi Nominee Ltd | London | 2025 |
| Catalka Ltd | Devon | 2023 |
| Catalogic Software Limited | Colindale | 2013 |
| Catalogue Beauty Limited | London | 2019 |
| Catalogue Returns Outlet Ltd | Knottingley | 2025 |
| Catalpa Capital Ltd | Dorchester | 2025 |
| Catalunya Golf Limited | Uxbridge | 1993 |
| Catalysis Ltd | Lancaster | 2023 |
| Catalysm Ltd | Isle Of Mull | 2020 |
| Catalyst 4 Professional Sports Management Limited | Newcastle Upon Tyne | 2017 |
| Catalyst Asset & Office Solutions Limited | Manchester | 2003 |
| Catalyst BNI Ltd | Liverpool | 2000 |
| Catalyst Business (UK) Ltd | Inverkeithing | 2014 |
| Catalyst Business Services Limited | Spalding | 2025 |
| Catalyst Carmarthenshire Ltd | Carmarthen | 2020 |
| Catalyst Coaching Ltd | Ruislip, | 2025 |
| Catalyst Consulting Services Limited | | 2007 |
| Catalyst Engine Ltd | Stalybridge | 2025 |
| Catalyst Network International CIC | Welwyn Garden City | 2023 |
| Catalyst Network of Churches | Coventry | 2012 |
| Catalyst Songs Limited | London | 2026 |
| Catalyst Space Limited | Basingstoke | 2019 |
| Catalyst Sports Management Limited | Harrow On The Hill | 2014 |
| Catalyst Stockton-On-Tees Limited | Stockton-On-Tees | 2000 |
| Catalyst Supplies Limited | Coventry | 1992 |
| Catalyst Therapy Services Ltd. | London | 2016 |