| C S Brown Ltd | Construction | 2025 |
| C S Industries Ltd | Water & waste | 2012 |
| C S Jones Electrical Ltd | Construction | 2026 |
| C Shemeld Carpentry Limited | Construction | 2002 |
| C T MAX Ltd | Real estate | 2018 |
| C T Services Nationwide Ltd | Construction | 2020 |
| C Taylor Solutions Ltd | Information & communication | 2017 |
| C Tech Rail Services Ltd | Manufacturing | 2021 |
| C Utley Services Ltd | Construction | 2015 |
| C W Contract Management Ltd | Professional & scientific | 2024 |
| C W Fletcher & Sons Limited | Manufacturing | 1908 |
| C&C Commercials Ltd | Wholesale & retail | 2019 |
| C&C Consultation Services Ltd | Professional & scientific | 2019 |
| C&C London (UK) Ltd | Construction | 2018 |
| C&D Boden Limited | Wholesale & retail | 2023 |
| C&D Electrical Solutions Ltd | Construction | 2025 |
| C&D JG Holdings Limited | Real estate | 2024 |
| C&Dk Properties Limited | Real estate | 2016 |
| C&F Commodities Ltd | Wholesale & retail | 2024 |
| C&H Alarms Ltd | Administrative & support | 2026 |
| C&J Plumbing and GAS Services Ltd | Construction | 2022 |
| C&J Properties (Yorkshire) Limited | Real estate | 2018 |
| C&K Green Limited | Professional & scientific | 2013 |
| C&K Nurseries Holding Ltd | Financial services | 2024 |
| C&L Hospitality Limited | Hospitality | 2024 |
| C&L Mechanical Limited | Construction | 2024 |
| C&L Transport Services Ltd | Transport & logistics | 2015 |
| C&M Accountancy Services Ltd | Professional & scientific | 2016 |
| C&N Property Group Ltd | Real estate | 2024 |
| C&R Pubs Ltd | Administrative & support | 2025 |
| C&S PUB Limited | Hospitality | 2024 |
| C'84 Brew Co Ltd. | Wholesale & retail | 2019 |
| C-Capsule Limited | Professional & scientific | 2022 |
| C-Ednajf Ltd | Education | 2019 |
| C-Line Hospitality Limited | Hospitality | 2022 |
| C. & S. Fabrications Limited | Manufacturing | 1983 |
| C. B. CNC Limited | Extraterritorial | 2005 |
| C. Greaves Plumbing and Heating Ltd | Construction | 2023 |
| C. M. Tiling Company Limited | Construction | 1997 |
| C. Rudrum & Sons (Cornwall) Limited | Wholesale & retail | 1962 |
| C. Shaw (Utilities) Ltd | Construction | 2016 |
| C.A.N.L. Ltd | Professional & scientific | 2019 |
| C.B. Kaymich & Co. Limited | Manufacturing | 1977 |
| C.B.S. (Sheffield) Ltd | Administrative & support | 2008 |
| C.E.C.H. Holdings Limited | Real estate | 2025 |
| C.F. Eadon Co. Limited | | 1977 |
| C.G.S Gems Ltd | Wholesale & retail | 2010 |
| C.I.&I. Services Limited | Mining & quarrying | 2013 |
| C.I.J. Limited | Real estate | 1947 |
| C.K. One Stop Roofing Sevices Ltd | Construction | 2018 |
| C.M.K & Sons Properties Ltd | Real estate | 2024 |
| C.M.S. GAS Limited | Other services | 2010 |
| C.Mallender Joinery Ltd | Construction | 2012 |
| C.R. Gibbs & Sons (Sheffield) Limited | Wholesale & retail | 1973 |
| C.R.L. Industries Limited | Construction | 1956 |
| C.S.Installations Ltd | Mining & quarrying | 2019 |
| C.T.V Ltd | Wholesale & retail | 2024 |
| C.T.W. (Holdings) Limited | Professional & scientific | 1985 |
| C.T.W. Hardfacing Limited | Manufacturing | 1972 |
| C.V. Gauges Limited | Extraterritorial | 1999 |
| C.V. Instruments Limited | Manufacturing | 1971 |
| C.W Davies Financial Consultancy Limited | Financial services | 2022 |
| C.W Davies Property Development Limited | Real estate | 2023 |
| C2 Estates Limited | Real estate | 2023 |
| C21 Consultancy Limited | Construction | 2019 |
| C2G Professional Development Ltd | Professional & scientific | 2021 |
| C3 Trust UK | Other services | 2006 |
| C6 Bikes Ltd | Wholesale & retail | 2014 |
| C60 Consulting Ltd | Professional & scientific | 2009 |
| Ca&T Trading (UK) Limited | Other services | 2018 |
| Caas Consulting Limited | Information & communication | 2015 |
| CAB Project Consulting Ltd | Information & communication | 2024 |
| CAB Safety Services Limited | Professional & scientific | 2024 |
| Cabable Connect Ltd | Transport & logistics | 2025 |
| Cabajo Ltd | Financial services | 2026 |
| Cabanova Limited | Financial services | 2020 |
| Cabinet Estates Ltd | Real estate | 2021 |
| Cabinet Investments Limited | Real estate | 2004 |
| Cable Carnage Limited | Arts & recreation | 2012 |
| Cable Construction Limited | Real estate | 2003 |
| Cabletek Limited | Construction | 2023 |
| Caboodle Delivery Limited | Administrative & support | 2020 |
| Cace Commercial Property Limited | Real estate | 2025 |
| Cactus Homes Ltd | Real estate | 2022 |
| Cactus Property Holdings LLP | | 2012 |
| Cactus Tech Consulting Limited | Information & communication | 2024 |
| Cadava Ltd | Transport & logistics | 2014 |
| Caddy Cabs Limited | Other services | 2024 |
| Caddy Clubhouse Ltd | Arts & recreation | 2024 |
| Caddycb Ltd | Construction | 2020 |
| Cadenza VM Ltd | Professional & scientific | 2007 |
| Cadesol Limited | Administrative & support | 2013 |
| Cadexpert Ltd | Professional & scientific | 2025 |
| Cadman & Townrow Roofing Specialists Ltd | Construction | 2012 |
| Cadman Enterprises Limited | Manufacturing | 2022 |
| Cadoworld Limited | Wholesale & retail | 2007 |
| Cadre (Midlands) Ltd | Administrative & support | 2020 |
| Cadre (Yorkshire & Humber) Ltd | Administrative & support | 2020 |
| Cadre Group UK Ltd | Administrative & support | 2019 |
| Cads South Yorkshire Limited | Arts & recreation | 2012 |