| Coastal OIL Tank Services Ltd | Water & waste | 2018 |
| Coastal Wall Ties Limited | Construction | 2012 |
| Coastline Air Conditioning Services Limited | Energy | 2026 |
| Coastline BP LLP | | 2012 |
| Codetide Limited | Information & communication | 2025 |
| Coffees & Creams. Ltd | Wholesale & retail | 2022 |
| Cognitive Diversity at Work Ltd | Professional & scientific | 2020 |
| Coldicott Mews Residents Limited | Households | 2009 |
| Colebrook Management Limited | Households | 1980 |
| Colgate & Gray Limited | Construction | 2013 |
| Colourful Content Ltd | Administrative & support | 2014 |
| Columbian House RTM Company Limited | Households | 2012 |
| Combined Leisure Solutions LLP | | 2021 |
| Commercial Dishwasher Repairs Ltd | Manufacturing | 2016 |
| Community Rides Ltd | Transport & logistics | 2026 |
| Compass Point (Eastbourne) Management Company Limited | Households | 1994 |
| Compost-A-Box Ltd | Extraterritorial | 2018 |
| Comtel Services Limited | Construction | 2000 |
| Condair Limited | Energy | 1982 |
| Conifers Hill Management Limited | Real estate | 2014 |
| Connect Electronics Limited | Wholesale & retail | 2019 |
| Conroy & Hoque Property Ltd | Real estate | 2026 |
| Continuum Media Holding Ltd | Information & communication | 2026 |
| Copoll (Brighton) Limited | Real estate | 1994 |
| Copper Tree Homes Ltd | Construction | 2021 |
| Copperbinx Ltd | Professional & scientific | 2025 |
| Coppets Wood Management Company Limited | Households | 1971 |
| Copse View Management Limited | Real estate | 1993 |
| COR Agri Ltd | Wholesale & retail | 2026 |
| Corite Technology Limited | Professional & scientific | 2017 |
| Cornerstone Renovation & Property Maintenance Limited | Construction | 2009 |
| Cornerways (Littlehampton) Resident's Association Limited | Households | 1970 |
| Cornwall Gardens(Littlehampton)Management Company Limited | Households | 1969 |
| Country Securities Ltd | Financial services | 1985 |
| County Landscapes Limited | Professional & scientific | 2002 |
| Courtyard House Estates Limited | Real estate | 2012 |
| CP Coaching Limited | Education | 2012 |
| Crayrose Properties Limited | Households | 1972 |
| Creamsoda Records Ltd | Information & communication | 2015 |
| Creative Design Services Limited | Professional & scientific | 1990 |
| Creative Heart Littlehampton CIC | Hospitality | 2019 |
| Creative Interior Projects Limited | Construction | 2023 |
| Creative Touch Group Limited | Education | 2018 |
| Crest Builders Limited | Construction | 2014 |
| Crest Maintenance Ltd | Construction | 2022 |
| Crew Shop Limited | Wholesale & retail | 2012 |
| Cris&Co Couriers Ltd | Transport & logistics | 2016 |
| Crowley Vehicle Leasing Ltd | Administrative & support | 2025 |
| Crown Roofing Sussex Ltd | Construction | 2024 |
| CRS Tanks Ltd | Water & waste | 2014 |
| Cryoskin Ltd | Wholesale & retail | 2017 |
| Cryosthetics Ltd | Other services | 2014 |
| Crystal Clear Fitness Ltd | Other services | 2018 |
| Crystal Elsol Tech PVT Ltd | Wholesale & retail | 2024 |
| CSV Consultants Limited | Professional & scientific | 2000 |
| CT Ecology Limited | Professional & scientific | 2017 |
| Cube Cat Ltd | Information & communication | 2013 |
| Cuboid Creations Ltd | Professional & scientific | 2024 |
| Cudlow Garden Residents' Association Limited | Households | 1965 |
| Cullingworth Properties Limited | Real estate | 2024 |
| Cullingworthholdings Limited | Financial services | 2021 |
| Curate Films Limited | Information & communication | 2017 |
| Custom Chess Company Limited | Manufacturing | 2013 |
| D Allery Gardening Services Limited | Administrative & support | 2005 |
| D Horn Revamps Ltd | Manufacturing | 2024 |
| D W Clarke Properties Limited | Real estate | 2015 |
| D W Properties (South East) Ltd | Real estate | 2014 |
| D-Unlimited Solutions Ltd | Construction | 2015 |
| D. J. (Creations) Limited | Wholesale & retail | 1987 |
| D. R & M Services Ltd | Transport & logistics | 2020 |
| D.H Outdoor Solutions Ltd | Construction | 2025 |
| D.S Plastering Services Ltd | Construction | 2025 |
| D.V.R. Construction Services Limited | Construction | 1975 |
| Dairy (Worthing) RTM Company Limited | Households | 2020 |
| Daisy Handley Limited | Professional & scientific | 2024 |
| DAN Kimber Studios Ltd | Professional & scientific | 2023 |
| Dane Acre Management Company Limited | Extraterritorial | 2007 |
| Darlingtons Estates Limited | Real estate | 2024 |
| Data Image (U.K.) Limited | Manufacturing | 1994 |
| David Dumigan Consulting Limited | Real estate | 2010 |
| Davies Business Consultancy Limited | Professional & scientific | 2018 |
| Davka Ltd | Financial services | 2011 |
| Davlia Construction Limited | Construction | 2022 |
| Davlic Media Ltd | Professional & scientific | 2014 |
| DCR Building & Landscapes Ltd | Construction | 2024 |
| Deaf & Disabled People in TV Ltd | Professional & scientific | 2021 |
| Dean Jones Funeral Service Ltd | Other services | 2021 |
| Dearden Homes Limited | Construction | 2004 |
| Dearden Investments Limited | Real estate | 2011 |
| Debb-On-Air Limited | Administrative & support | 2001 |
| Debbie Kirk Consultancy Ltd | Professional & scientific | 2015 |
| Decadent Decaf Coffee Company Limited | Manufacturing | 2015 |
| Deco 8 Management Limited | Households | 2014 |
| Dedbest Distillery Co. Ltd | Manufacturing | 2021 |
| Defiant Events Ltd | Arts & recreation | 2021 |
| Delay RAY Limited | Wholesale & retail | 2025 |
| Dellner Property UK Consett Limited | Real estate | 2025 |
| Delta Comms Limited | | 1987 |
| Demayor UK Ltd | Health & social care | 2022 |
| Democracy Movement | Other services | 1998 |