| Colshaz Limited | Administrative & support | 2002 |
| COM TEC Engineering Limited | Construction | 2018 |
| Comet Alliance Ltd | Other services | 2024 |
| COMFYROOMS2RENT Ltd | Real estate | 2024 |
| Comlec Ltd | Information & communication | 2014 |
| Commercial Entertainments Limited | Information & communication | 2021 |
| Commercial Facilities Engineers Limited | Administrative & support | 2012 |
| Commercial Property and Storage Limited | Construction | 2012 |
| Complete Project Solutions Ltd | Professional & scientific | 2005 |
| Complete Renovations (Sussex) Ltd | Construction | 2024 |
| Complete TM Ltd | Administrative & support | 2019 |
| Component Process and Repair Limited | Professional & scientific | 1990 |
| Composite Coating Solutions Ltd | Construction | 2025 |
| Compton Court (Eastbourne) Limited | Households | 1988 |
| Connaught House RTM Company Limited | Households | 2006 |
| CONNECTED2 Limited | Administrative & support | 2018 |
| CONNECTED2CARE Ltd | Health & social care | 2025 |
| Connecting.Tech Ltd | Information & communication | 2023 |
| Connection Bridge Ltd | Professional & scientific | 2024 |
| Conrad Groundworks Ltd | Construction | 2024 |
| Constant Projects Ltd | Wholesale & retail | 2020 |
| Construct & Connect Ltd | Construction | 2024 |
| Construction Diagnostics Limited | Professional & scientific | 2024 |
| Construction Lifting Ltd | Construction | 2023 |
| Consultaid CIC | Professional & scientific | 2010 |
| Consultdarcy Ltd | Professional & scientific | 2014 |
| Contemporary Architectural Glazing Ltd | Construction | 2023 |
| CONTRACTORS4CONTRACTORS Ltd | Extraterritorial | 2026 |
| Cooperative HR Ltd | Administrative & support | 2017 |
| Coppins Court (Management) Limited | Households | 1980 |
| Copy Catalyst Ltd | Extraterritorial | 2023 |
| Corbett Vision Ltd | Real estate | 2014 |
| Corbil Planning Ltd | Professional & scientific | 2016 |
| Core Games Ltd | Arts & recreation | 2026 |
| Cormorant Coffee Company Ltd | Hospitality | 2026 |
| Cornerstone Capital Projects Ltd | Other services | 2018 |
| Corporate Financial Resources LLP | | 2011 |
| Couldwell Developments Limited | Construction | 2010 |
| Coulter Electrical Ltd | Construction | 2018 |
| Counterpoint Productions Ltd | Information & communication | 2007 |
| Countland Court Limited | Households | 1981 |
| Countregis Limited | Households | 2010 |
| County Footwear Limited | Wholesale & retail | 1997 |
| Cozens and Nicholson (Heating & Plumbing) Limited | Construction | 1998 |
| CPI Moling Limited | Construction | 2000 |
| CPS Property Group Limited | Real estate | 2025 |
| Cranes Properties South Ltd | Households | 2025 |
| Cranford Accountants Ltd | Professional & scientific | 2020 |
| Crazy Golf Design Limited | Construction | 2022 |
| CRD Restaurant Ltd | Hospitality | 2025 |
| Creating Visions Carpentry Service's Ltd | Extraterritorial | 2025 |
| Creative Building & Refurbishments Ltd | Construction | 2019 |
| Creative Lettings Limited | Real estate | 2009 |
| Creative Thatching Ltd | Construction | 2024 |
| Cresco Media Ltd | Professional & scientific | 2022 |
| Crime Science Limited | Information & communication | 2025 |
| Crip 2 Limited | Arts & recreation | 2025 |
| Crocus Enterprise Limited | Wholesale & retail | 2014 |
| Crocus Select Limited | Wholesale & retail | 2025 |
| Croft & Combe Ltd | Manufacturing | 2026 |
| Croft Builders Ltd | Construction | 2016 |
| Cropp & Farr Jewellery Limited | Wholesale & retail | 2016 |
| Cross 2 Consultancy Limited | Professional & scientific | 2015 |
| Crossknowledge Foundation | Professional & scientific | 2012 |
| Crosthwaite & SON Limited | Construction | 2014 |
| Crouchers Group Ltd | Construction | 2009 |
| Crow & Crow Construction Ltd | Construction | 2022 |
| Crow Consultancy Services Ltd | Professional & scientific | 2018 |
| Crowe Engineering Ltd | Professional & scientific | 2025 |
| Crown Properties West Sussex Limited | Real estate | 2014 |
| CRS Group (Services) Ltd | Administrative & support | 2022 |
| CRS Group Holdings Ltd | Administrative & support | 2022 |
| CRS Group North Ltd | Administrative & support | 2022 |
| Crunch Sandwich Bar Ltd | Hospitality | 2025 |
| CST Tredz Limited | Wholesale & retail | 2024 |
| CTL Electrical Installations Limited | Construction | 2015 |
| CUBE17 Ltd | Professional & scientific | 2008 |
| Culford Estates Ltd | Real estate | 2025 |
| Cullenglow Limited | Financial services | 1976 |
| Cultural Communications Limited | Professional & scientific | 2013 |
| Curry Twist Bognor Regis Ltd | Hospitality | 2024 |
| Cyber Butler Limited | Information & communication | 2017 |
| Cyber Squirrel CIC | Information & communication | 2010 |
| Cybis Limited | Information & communication | 1994 |
| Cylenchar Limited | Professional & scientific | 2004 |
| Cypress Way (Aldwick) Limited | Households | 2013 |
| D & S Housing Limited | Hospitality | 2002 |
| D & T Electrical (Felpham) Ltd | Construction | 2014 |
| D and D Properties Southern Ltd | Real estate | 2026 |
| D and J Holman Consulting Ltd | Professional & scientific | 2023 |
| D Ashcroft Properties Limited | Real estate | 2025 |
| D B M Building Services Limited | Construction | 2012 |
| D Cooper Underwater Services Limited | Arts & recreation | 2013 |
| D Potter Investments Limited | Real estate | 2022 |
| D Webb Electrics Limited | Construction | 2018 |
| D&C Brock Limited | Wholesale & retail | 2020 |
| D&D Littlehampton Limited | Wholesale & retail | 2017 |
| D&D Services Southern Limited | Construction | 2025 |
| D&G Interiors Ltd | Professional & scientific | 2011 |
| D&M Market Limited | Wholesale & retail | 2026 |