| Cost Reduction Warehouse 2 Ltd | Administrative & support | 2021 |
| Costa (2020) UK Assets Ltd | Real estate | 2020 |
| Cosys Holdings Ltd | Financial services | 2024 |
| Cosys Ltd | Professional & scientific | 2019 |
| Cotswold Court (Eastbourne) Ltd | Real estate | 2009 |
| Country Associates Limited | Health & social care | 2019 |
| Courdale Heritage Limited | Professional & scientific | 2023 |
| Courierwise Ltd | Transport & logistics | 2012 |
| Course Accreditation Ltd | Education | 2022 |
| Courtlands Road Property Management Company Limited | Other services | 2004 |
| Cove Coastal Living Ltd | Wholesale & retail | 2022 |
| Covert Protection Ltd | Administrative & support | 2019 |
| Coverwell Fire and Security Ltd | Financial services | 2004 |
| CP Connection Services Ltd | Construction | 2025 |
| CP Jones Plumbing Ltd | Construction | 2013 |
| CPC Interiors Ltd | Construction | 2012 |
| CR Construction and Development Limited | Construction | 2018 |
| CRA Management Company Limited | Real estate | 2004 |
| Craft Brickwork Limited | Construction | 2018 |
| Craftingold Limited | Manufacturing | 2003 |
| Cramp & Mullaney LLP | | 2013 |
| Cranbrook Fishmongers Limited | Wholesale & retail | 2016 |
| Cranbrook Press Ltd | Information & communication | 2023 |
| Cranmill Designs (Sussex) Limited | Professional & scientific | 2000 |
| Cranston Consultants Limited | Professional & scientific | 2023 |
| Crawford Advisory Limited | Financial services | 2024 |
| Crawley Auto Drive Limited | Education | 2022 |
| Crayford Weights and Fitness Limited | Arts & recreation | 2009 |
| Creating Homes Limited | Construction | 2014 |
| Creative Courage Projects & Consulting Limited | Health & social care | 2014 |
| Creative Fever Ltd | Arts & recreation | 2025 |
| Creatology Limited | Professional & scientific | 2017 |
| Creb Ltd | Hospitality | 2007 |
| Creedcorp Property Holdings Limited | Financial services | 2020 |
| Creek Road Holdings Limited | Real estate | 2019 |
| Crema DEL Cafe Ltd | Hospitality | 2025 |
| Crenden House Management Company Limited | Real estate | 2015 |
| Creno Ventures Ltd | Real estate | 2024 |
| Crepes DE LA Creme Ltd | Hospitality | 2019 |
| Cricket District Limited | Information & communication | 2020 |
| Critical Design Solutions Ltd | Professional & scientific | 2019 |
| CRO Care Ltd | Administrative & support | 2018 |
| Croasis Limited | Real estate | 2025 |
| Crocombe Property Group Ltd | Real estate | 2024 |
| Croft Court Eastbourne Residents Association Limited | Households | 1970 |
| Crofton Martin Ltd | Real estate | 2020 |
| Croham Cliff 15 Darley Road Limited | Households | 2003 |
| Crossfield Properties Sussex Limited | Real estate | 2022 |
| Crossing the Screen Community Interest Company | Information & communication | 2025 |
| Crowley White Limited | Financial services | 2015 |
| Crown & Anchor (Eastbourne) Ltd | Hospitality | 2014 |
| Crown and Hound Ltd | Other services | 2023 |
| Crownstone Management Ltd | Households | 2025 |
| Croydon Services Limited | Manufacturing | 2024 |
| CRP Auto Ltd | Wholesale & retail | 2021 |
| Cryntora Ltd | Information & communication | 2025 |
| Cryptoknight Ltd | Financial services | 2019 |
| Crystal Air Conditioning and Maintenance Services Limited | Professional & scientific | 2010 |
| Crystal Air Conditioning Limited | Professional & scientific | 2019 |
| Crystals & Candles Ltd | Wholesale & retail | 2021 |
| CS Day Plumbing and Heating Ltd | Construction | 2022 |
| Csie Properties Ltd | Real estate | 2024 |
| CSJ Finch Ltd | Health & social care | 2019 |
| CTG Gaming Ltd | Wholesale & retail | 2025 |
| Cttc Holdings Ltd | Professional & scientific | 2019 |
| Cuban Atmosphere Limited | Extraterritorial | 2023 |
| Cucina Italiana Ltd | Hospitality | 2018 |
| Cuckmere Bike Barn Limited | Administrative & support | 2020 |
| Cuckmere Cottages and Camping Limited | Hospitality | 2024 |
| Cuckmere Credit Collections Ltd | Administrative & support | 2012 |
| Cuckmere Enterprises Holdings Limited | Real estate | 2018 |
| Cuckmere Enterprises Partnership LLP | | 2018 |
| Cuckmere Land Limited | Real estate | 2022 |
| Cuckoo Fayre Limited | Arts & recreation | 1991 |
| Cuckoo Hair Ltd | Other services | 2014 |
| Cuesta Torres Limited | Information & communication | 2024 |
| CUG Travel Ltd | Administrative & support | 2021 |
| Cumballa Court Eastbourne Limited | Households | 2005 |
| Curtis Electrical Contractors Ltd | Construction | 2024 |
| Custard Ltd | Manufacturing | 2010 |
| Custom Build (Sussex) Limited | Construction | 2004 |
| Custom Lunches Limited | Hospitality | 2008 |
| CUT and FIX Carpentry Ltd | Manufacturing | 2014 |
| Cute Holdings LLP | | 2016 |
| Cute Media Corporation Ltd | Information & communication | 2008 |
| Cute Media Group Limited | Financial services | 2009 |
| Cutting Edge HS Limited | Other services | 2003 |
| Cutting Edge Lawns and Landscaping Ltd | Administrative & support | 2018 |
| Cuttlers Ltd | Administrative & support | 2019 |
| Cutty & Car Limited | Health & social care | 2013 |
| CVT Market Access Solutions Ltd | Professional & scientific | 2024 |
| CWN Design Ltd | Professional & scientific | 2019 |
| CWT Investments Limited | Real estate | 2024 |
| Cybernomics Limited | Information & communication | 2012 |
| Cymba Unified Limited | Other services | 2023 |
| D & C Developments Ltd | Real estate | 2024 |
| D & S Enterprises (Tenterden) Limited | Wholesale & retail | 2007 |
| D C Tran Enterprises Limited | Wholesale & retail | 2025 |
| D Collective Ltd | Health & social care | 2020 |
| D F Organisation Limited | Administrative & support | 2012 |