| Copernicium 1439 Limited | Manufacturing | 2020 |
| Copia Talent Limited | Administrative & support | 2024 |
| Copper Aviation Ltd | Transport & logistics | 2026 |
| Copper Works Plumbing and Heating Limited | Construction | 2023 |
| Copse Mill Holdings Limited | Professional & scientific | 2002 |
| Copse Mill Pension Nominees Ltd | Administrative & support | 2006 |
| Copse Mill Properties Limited | Construction | 1993 |
| Copsemill Wright Ltd | Construction | 2017 |
| Cora Lifts Limited | Administrative & support | 2007 |
| Core Coders Ltd | Information & communication | 2008 |
| Core Electrical Services (Southern) Ltd | Construction | 2012 |
| Core Physio and Fitness Limited | Health & social care | 2016 |
| Core Services South Limited | Administrative & support | 2018 |
| Corinne Elizabeth Ltd | Other services | 2023 |
| Corkwood Services Limited | Households | 1987 |
| Cormorant Bars Limited | Hospitality | 2012 |
| Corner Entertainment Limited | Hospitality | 2024 |
| Cornerstone Plumbing and Heating Limited | Construction | 2022 |
| Cornwall Trade Parts Specialists (TPS) Limited | Wholesale & retail | 2007 |
| Corporate Home Away (South) Limited | Households | 2018 |
| Corrie Maccoll Limited | Financial services | 1951 |
| Corrie Maccoll Rubber Ltd | Administrative & support | 2017 |
| Corshaw Developments Limited | Construction | 2013 |
| Cortabella Limited | Real estate | 2019 |
| Corvi Ltd | Other services | 2024 |
| Corvus Advisers Limited | Professional & scientific | 2020 |
| Corvus Group (UK Administration) Limited | Financial services | 2024 |
| Corvus Group (UK Holdings) Limited | Financial services | 2024 |
| Cosmos Traders Limited | Manufacturing | 2020 |
| Coughlan and SON Developments Ltd | Construction | 2018 |
| Coughlan Construction Ltd | Construction | 2018 |
| Coughlan Developments Ltd | Construction | 2012 |
| Couk Limited | Professional & scientific | 2011 |
| Countermac Limited | Information & communication | 2019 |
| Counterpoint MTC Ltd | Administrative & support | 2000 |
| County Building Control Limited | Professional & scientific | 2015 |
| County Business Clubs Sussex Limited | Professional & scientific | 2020 |
| County Roads Ltd | Construction | 2012 |
| County Shoe Repairs Limited | Wholesale & retail | 2002 |
| Couple Keys Limited | Information & communication | 2020 |
| Courier Express Limited | Transport & logistics | 2002 |
| Courtacre Limited | Administrative & support | 2006 |
| Courtlands Independent Special School Ltd | Education | 2023 |
| Cousin Developers Limited | Construction | 2023 |
| Coventina Close Management Company Limited | Construction | 2014 |
| Cover Assured Limited | Financial services | 2018 |
| Coverwatch Ltd | Public administration | 2018 |
| Cowabunga Limited | Professional & scientific | 2020 |
| Cowabunga Toys and Collectables Limited | Wholesale & retail | 2025 |
| Cowdray Court Management Limited | Households | 1995 |
| Cowland Investments Limited | Real estate | 2025 |
| COX Holdings (Sussex) Limited | Financial services | 2026 |
| CP Assets Ltd | Real estate | 2024 |
| CPD Training Solutions Ltd | Health & social care | 2008 |
| Cptl Ltd | Wholesale & retail | 2020 |
| Craft Beer Management Ltd | Administrative & support | 2016 |
| Craftd Holdings Ltd | Financial services | 2025 |
| Craftd London Ltd | Manufacturing | 2018 |
| Crafted by Cole Ltd | Manufacturing | 2019 |
| Crafted Created Ltd | Wholesale & retail | 2020 |
| Craftisaurus Ltd | Wholesale & retail | 2025 |
| Craftmaster Social Ltd | Hospitality | 2018 |
| Crafty Hair Limited | Other services | 2025 |
| Crafty Worthing Limited | Arts & recreation | 2013 |
| Craigsailing Community Interest Company | Health & social care | 2020 |
| Cranbrook Trinity Consultancy Ltd | Administrative & support | 2018 |
| Cranford Construction & Development Limited | Construction | 1980 |
| Crank Cycle Coaching Ltd | Arts & recreation | 2021 |
| CRATE47 Limited | Manufacturing | 2012 |
| Crawfords Community Housing Ltd | Real estate | 2026 |
| Crawfords Homes Limited | Health & social care | 2002 |
| Crawley Roofing Ltd | Construction | 2026 |
| Crayston Consulting Limited | Information & communication | 2007 |
| Crazylegs Rigging Ltd | Arts & recreation | 2011 |
| CREA8ION Limited | Information & communication | 2022 |
| Create BTN Ltd | Administrative & support | 2024 |
| Create Your Life Limited | Information & communication | 2019 |
| Createworks Ltd | Professional & scientific | 2021 |
| Creating Spaces Design & Build Ltd | Construction | 2019 |
| Creative Attic Solutions Hove Limited | Construction | 2019 |
| Creative BIZ Weirdos Ltd | Manufacturing | 2025 |
| Creative Digital Media Limited | Information & communication | 2021 |
| Creative Funding Limited | Financial services | 2013 |
| Creative Funding Solutions (Holdings) Limited | Financial services | 2021 |
| Creative Funding Solutions Limited | Financial services | 2009 |
| Creative Garden Rooms (Southern) Ltd | Construction | 2025 |
| Creative Heating Ltd | Construction | 2006 |
| Creative Hire Solutions Limited | Administrative & support | 2014 |
| Creative Instrumentation Limited | Manufacturing | 1970 |
| Creative Link Studio Ltd | Information & communication | 2014 |
| Creative Waves Community Arts CIC | Arts & recreation | 2011 |
| Creatives Across Sussex C.I.C. | Arts & recreation | 2013 |
| Creativetalksai Ltd | Professional & scientific | 2025 |
| Creativity Sown Limited | Information & communication | 2020 |
| Creator Access Limited | Other services | 2025 |
| Creator GC Events Limited | Arts & recreation | 2025 |
| Crebbits Ltd | Financial services | 2023 |
| Credential PTL Limited | Water & waste | 2008 |
| Crescent Accountancy Services Ltd | Professional & scientific | 2019 |
| Crescent Nava Limited | Wholesale & retail | 2025 |