| Collector's Edge Ltd | Wholesale & retail | 2024 |
| College Close Handcross Management Company Limited | Households | 1996 |
| Collingwood Ecoware Limited | Wholesale & retail | 2016 |
| Colorco (Wallpaper & Paints) Limited | Wholesale & retail | 1975 |
| Colossus Systems Limited | Information & communication | 2018 |
| Comber's Coffee Ltd | Hospitality | 2024 |
| Comfort Paradise Limited | Wholesale & retail | 2025 |
| Comfort Taxis Haywards Heath Ltd | Transport & logistics | 2026 |
| Comfort Thread Limited | Other services | 2026 |
| Commercial Software Limited | Information & communication | 1983 |
| Commonwealthcrees Ltd | Administrative & support | 2023 |
| Communitech Group Limited | Information & communication | 2021 |
| Community Music ROK Skool CIC | Education | 2022 |
| Compact Structure Ltd | Construction | 2019 |
| Company 129 Limited | Real estate | 2025 |
| Compass Development Consulting Ltd | Construction | 2023 |
| Compass Vehicle Services Limited | Administrative & support | 1999 |
| Competidor Ltd | Arts & recreation | 2013 |
| Competitive Holidays Limited | Administrative & support | 2016 |
| Completehr Limited | Professional & scientific | 2000 |
| Completely PC Limited | Other services | 1997 |
| Compton Global Investments Ltd | Real estate | 2014 |
| Computing Scientific Ltd | Information & communication | 2019 |
| Concentia Limited | Professional & scientific | 2004 |
| Concept. Create. Ltd | Construction | 2021 |
| Conecon UK Ltd | Professional & scientific | 2012 |
| Configure Accounting Limited | Professional & scientific | 2017 |
| Connections Residential Letting Agents Ltd | Real estate | 2007 |
| Connectki Ltd | Information & communication | 2019 |
| Connectxv Ltd | Information & communication | 2026 |
| Connorboorepov Ltd | Information & communication | 2025 |
| Conquest Engineering Limited | Administrative & support | 2016 |
| Conquest Spaces Limited | Real estate | 2022 |
| Conservatory Wise (Sussex) Limited | Construction | 2011 |
| Conspectus Capital Limited | Professional & scientific | 2020 |
| Constama Ltd | Arts & recreation | 2026 |
| Constant K Ltd | Professional & scientific | 2025 |
| Constructive Conservation Limited | Extraterritorial | 2008 |
| Contren Limited Liability Partnership | | 2005 |
| Control IT Limited | Professional & scientific | 2008 |
| Conundrum Ltd | Professional & scientific | 2025 |
| Convert Ltd | Manufacturing | 2005 |
| Cool 4 School Clubs Ltd | Health & social care | 2022 |
| Coolblast Limited | Wholesale & retail | 2024 |
| Cooper Ballard Advisory Ltd | Professional & scientific | 2024 |
| Coopers Paraplanning Ltd | Administrative & support | 2012 |
| Copper & ELM Ltd | Professional & scientific | 2020 |
| Copperwood Court (Sydney Road Haywards Heath) Company Limited | Professional & scientific | 2013 |
| Copthorne Classic Garage Ltd | Wholesale & retail | 2016 |
| Copthorne Massage Clinic Ltd | Other services | 2026 |
| Copygate Limited | Information & communication | 1982 |
| Core Site Supplies Ltd | Wholesale & retail | 2026 |
| Coresense Consulting Ltd | Information & communication | 2015 |
| Corinthian Rubber UK Ltd | Agriculture & fishing | 2021 |
| Cornelius Groundworks & Landscaping Ltd | Administrative & support | 2024 |
| Corner Consulting Ltd | Professional & scientific | 2022 |
| Cornerpoint Property Consultants Limited | Real estate | 2014 |
| Cornerstone Place (Rochdale) Limited | Construction | 2024 |
| Cornerstone Place Developments Limited | Construction | 2023 |
| Cornerstone Place Limited | Construction | 2019 |
| Cornerstone Place Projects Limited | Construction | 2026 |
| Cornflake Club Limited | Health & social care | 2023 |
| Cornforth Consulting Ltd | Administrative & support | 2012 |
| Cornhill Consulting Limited | Professional & scientific | 2007 |
| Corpias Limited | Financial services | 2009 |
| Corporate Coaching Limited | Professional & scientific | 2001 |
| Corporate Transformation Limited | Professional & scientific | 1992 |
| Corrie Energy Partners Ltd | Manufacturing | 2018 |
| Corrin House (Maintenance) Company Limited | Households | 1963 |
| Costells Wood Residents Association Limited | Real estate | 1979 |
| Cotswold Investments Limited | Real estate | 2018 |
| Country House Cleaning Ltd | Administrative & support | 2022 |
| Cove Reformer Studio Limited | Other services | 2024 |
| Covertime Limited | Financial services | 2024 |
| COW Palace Ltd | Information & communication | 2017 |
| Cowabucha Ltd | Manufacturing | 2026 |
| Cowdraychef Limited | Hospitality | 2024 |
| CP Heating Services Ltd | Construction | 2017 |
| CR25 Limited | Professional & scientific | 2015 |
| Craen Enterprises Ltd | Professional & scientific | 2017 |
| Crafthousecoffee Ltd | Manufacturing | 2015 |
| Cranleigh Auto Bodyshop Ltd | Wholesale & retail | 2023 |
| Cranwell Coaching Limited | Other services | 2022 |
| Crasmundo Ltd | Information & communication | 2014 |
| Crawfield Properties Limited | Administrative & support | 2013 |
| Crawley Electrical Ltd | Construction | 2025 |
| Crawley Industrial Services Limited | Manufacturing | 2026 |
| Crawley Mechanical Handling Limited | Manufacturing | 1979 |
| CRC Medical Limited | Health & social care | 2015 |
| Creataly Ltd | Information & communication | 2025 |
| Create South East Limited | Construction | 2016 |
| Creative POD Ltd | Professional & scientific | 2005 |
| Creative Reach Ltd | Administrative & support | 2013 |
| Creative Writing for Social Change Ltd | Education | 2025 |
| Creator Engine Limited | Information & communication | 2025 |
| Creator International Limited | Construction | 1992 |
| Credit Risk Services Limited | Administrative & support | 2017 |
| Credos Consulting Limited | Professional & scientific | 2015 |
| Creedy Limited | Professional & scientific | 2023 |
| Crestline Worldwide Ltd | Professional & scientific | 2026 |