| Crowborough Specsavers Limited | Wholesale & retail | 2022 |
| Crown Developments (Winchester) Ltd | Construction | 2000 |
| Crown Gardens and Landscapes Limited | Extraterritorial | 2015 |
| Crown Oak Homes (UK) Limited | Real estate | 2017 |
| Crown Point Leeds Specsavers Limited | Wholesale & retail | 2012 |
| Crown Worth DIY Ltd | Manufacturing | 2024 |
| Crowndawn Limited | Professional & scientific | 1962 |
| Croydon Northend Visionplus Limited | Wholesale & retail | 1999 |
| Croydon Specsavers Hearcare Limited | Wholesale & retail | 2017 |
| Croydon Specsavers Limited | Wholesale & retail | 1988 |
| Croydon Visionplus Limited | Wholesale & retail | 1994 |
| Crucial Automatics Limited | Wholesale & retail | 2003 |
| Cruiseology Ltd | Administrative & support | 2022 |
| Crumb Pet Limited | Professional & scientific | 2016 |
| Crumbs Drinks Ltd | Manufacturing | 2019 |
| Crusader Fire Protection Limited | Construction | 1993 |
| Crusader Medical Care Properties Holdings Limited | Health & social care | 2020 |
| Crusader Medical Care Properties Limited | Real estate | 2020 |
| Crux Capital Group Ltd | Financial services | 2026 |
| Cruz and Greyson Group Ltd | Extraterritorial | 2019 |
| Crystal Clear Logic Ltd | Information & communication | 2018 |
| Crystal Ocean Carpentry Ltd | Manufacturing | 2023 |
| Crystal Peaks Specsavers Hearcare Limited | Wholesale & retail | 2007 |
| Crystal Peaks Specsavers Limited | Wholesale & retail | 1996 |
| Crystal Peaks Visionplus Limited | Wholesale & retail | 1996 |
| CSC Consultancy Ltd. | Administrative & support | 2024 |
| CSG Consultancy Ltd | Professional & scientific | 2012 |
| CSH Projex Limited | Professional & scientific | 2025 |
| Csiw Holdings Limited | Financial services | 2023 |
| CSS Group Limited | Financial services | 2006 |
| CSS Locksmiths Limited | Extraterritorial | 1970 |
| CSS On-Trade Limited | Wholesale & retail | 2008 |
| CSS Total Security Limited | Manufacturing | 1989 |
| CT UK Residential Real Estate Limited | Financial services | 2021 |
| CTH Enterprises Limited | Hospitality | 2019 |
| Cube (Southern) Ltd | Other services | 2025 |
| Cube Accountancy Ltd | Professional & scientific | 2011 |
| Cubic Carpentry Limited | Construction | 2018 |
| Cubik Wealth Management Limited | Financial services | 2024 |
| Cuckoo K9 Ltd | Agriculture & fishing | 2020 |
| Culbin Advisory Ltd | Information & communication | 2026 |
| Cullerne Aviation Services Limited | Transport & logistics | 2011 |
| Cumbernauld Specsavers Limited | Wholesale & retail | 2001 |
| Cumbernauld Visionplus Limited | Wholesale & retail | 2002 |
| Cumnock Specsavers Limited | Wholesale & retail | 2025 |
| Cupar Specsavers Limited | Wholesale & retail | 2018 |
| Cura Commercial (Holdings) Limited | Financial services | 2024 |
| Cura Commercial Limited | Construction | 2016 |
| Cura Electrical Limited | Construction | 2020 |
| Cura Homecare Limited | Administrative & support | 2012 |
| Curo Financial Limited | Professional & scientific | 2013 |
| Currency Research Limited | Professional & scientific | 2001 |
| Curryngrill Catering Services Ltd | Hospitality | 2023 |
| Cursive Consulting Limited | Professional & scientific | 2016 |
| Curtis & Co Property Renovations Ltd | Construction | 2022 |
| Curvica Limited | Information & communication | 2000 |
| Curzon Creative Ltd | Professional & scientific | 2020 |
| Custom Web Solutions Ltd | Information & communication | 2020 |
| CUT to the Smoke Limited | Wholesale & retail | 2020 |
| Cutmore & Leadbetter Funeral Directors Ltd | Other services | 2018 |
| Cutmore Family Funeral Directors Ltd | Administrative & support | 2012 |
| Cutting Edge Carpentry Services Limited | Construction | 2015 |
| CVC (Hampshire) Limited | Administrative & support | 2013 |
| Cwmbran Specsavers Hearcare Limited | Wholesale & retail | 2007 |
| Cwmbran Specsavers Limited | Wholesale & retail | 1991 |
| Cwmbran Visionplus Limited | Wholesale & retail | 1999 |
| CWR+ Ltd | Manufacturing | 2026 |
| CX Portsmouth Ltd | Education | 2024 |
| CXP Development Limited | Information & communication | 2018 |
| Cyan Power Commercial Property Management Limited | Real estate | 2009 |
| Cyan Power Limited | Real estate | 2007 |
| Cyber Espion Ltd | Information & communication | 2018 |
| Cyber Nomad Records Limited | Information & communication | 2026 |
| Cybersight Ltd | Information & communication | 2017 |
| Cyberthreat Red Limited | Information & communication | 2018 |
| Cynetix Ltd | Information & communication | 2021 |
| Cynosure Developments Limited | Real estate | 2017 |
| Cyntrol Systems Ltd | Construction | 2017 |
| Cypher Coding Limited | Education | 2016 |
| CZO Trans Ltd | Transport & logistics | 2023 |
| D & J Plumbing and Heating London Limited | Construction | 2026 |
| D & L Acquisitions Ltd | Health & social care | 2017 |
| D & LS Contracting Ltd | Administrative & support | 2019 |
| D & S Garden Supplies Limited | Wholesale & retail | 2021 |
| D a Eldridge & SON Limited | Construction | 2006 |
| D a Marine Carpentry Ltd | Construction | 2025 |
| D and G Media Limited | Other services | 2008 |
| D B Quantity Surveying Limited | Professional & scientific | 2013 |
| D C W Boat Repairs Ltd | Manufacturing | 2011 |
| D Draper Autocare Centre Limited | Wholesale & retail | 2012 |
| D J E Group Holdings Limited | Financial services | 2018 |
| D P Cooling Limited | Construction | 2025 |
| D V Marlow Holdings Limited | Financial services | 2024 |
| D&A Marine Carpentry Ltd | Construction | 2019 |
| D&B Civils North Limited | Construction | 2022 |
| D&D Brickwork Ltd | Construction | 2018 |
| D&V Globalnet Agency Ltd | Professional & scientific | 2025 |
| D'Cruze Agency Limited | Other services | 2025 |
| D'Vinci Group Holdings Limited | Financial services | 2025 |
| D'Vinci Group Limited | Financial services | 2023 |