| CRH Media Ltd | Information & communication | 2023 |
| Crimson Carrot Limited | Professional & scientific | 2021 |
| CRM Technologies Limited | Professional & scientific | 1999 |
| Crocodile Car Agents Ltd | Wholesale & retail | 2019 |
| Crocodile Inns Limited | Hospitality | 2017 |
| Croft Court Residents Association Limited | Households | 1984 |
| Cross Border Consultancy Limited | Professional & scientific | 2012 |
| Cross Origin Limited | Professional & scientific | 2019 |
| Crossfit Haywards Heath Ltd | Arts & recreation | 2021 |
| Crouch Fields (Ansty) Management Company Limited | Households | 2018 |
| Crowe Livestock Underwrting Services Limited | Financial services | 2022 |
| Crowmotion Limited | Information & communication | 2012 |
| Crown Civil Engineering Sussex Ltd | Construction | 2023 |
| Crown Services Group Limited | Construction | 2025 |
| Crowtherwood Limited | Professional & scientific | 1979 |
| Croydon Scrap Metal Limited | Administrative & support | 2019 |
| Cruiseway Limited | Administrative & support | 1982 |
| Crunch Technologies International Limited | Information & communication | 2023 |
| CSL Behring Holdings Limited | Wholesale & retail | 1995 |
| CSL Behring UK Limited | Wholesale & retail | 1982 |
| CSL Finance PLC | Professional & scientific | 2002 |
| Csmg Limited | Professional & scientific | 1998 |
| Cuckfield Bathrooms Limited | Wholesale & retail | 2015 |
| Cuckfield Bookfest Community Interest Company | Arts & recreation | 2019 |
| Cuckfield Coffee Ltd | Manufacturing | 2022 |
| Cuckfield Golf Centre Limited | Arts & recreation | 2018 |
| Cuckfield Lawn Tennis Club Ltd | Arts & recreation | 2014 |
| Cuckfield Plumbing & Heating Engineers Limited | Construction | 2020 |
| Cuckfield Roofing Ltd | Construction | 2023 |
| CUE Marketing Limited | Professional & scientific | 2024 |
| Culberry Nursery Limited | Agriculture & fishing | 1950 |
| Culture Ecosystem Ltd | Professional & scientific | 2025 |
| Cumnock Services UK Limited | Administrative & support | 2023 |
| Cumnor House School Trust | Education | 1989 |
| Curiosity Communications Ltd | Professional & scientific | 2023 |
| Currawong Limited | Information & communication | 2004 |
| Curry House 58 Ltd | Hospitality | 2018 |
| Custom Physique Limited | Other services | 2015 |
| Cut&Pitch Carpentry Ltd | Manufacturing | 2025 |
| CWP Ltd | Administrative & support | 2016 |
| CWP Residential LLP | | 2009 |
| Cxmpute Limited | Information & communication | 2025 |
| Cyber-Sec-Uk Ltd | Information & communication | 2022 |
| Cybersec Recruitment Solutions Ltd | Administrative & support | 2024 |
| Cybrio Ltd | Information & communication | 2024 |
| Cynosec Ltd | Information & communication | 2011 |
| D & K Dawson Holdings Limited | Real estate | 2020 |
| D and B Asset Management Ltd | Financial services | 2016 |
| D and B Engineering Ltd | Professional & scientific | 2016 |
| D and B Militaria Ltd | Wholesale & retail | 2006 |
| D and B Property 1 Limited | Real estate | 2025 |
| D and B Property 2 Limited | Real estate | 2025 |
| D and B Property 3 Limited | Real estate | 2025 |
| D and B Property Development Ltd | Construction | 2011 |
| D G TEL Communications Ltd | Information & communication | 2014 |
| D Holford Building Services Ltd | Construction | 2020 |
| D J Business Services Limited | Professional & scientific | 2012 |
| D J Nichols Transport Limited | Transport & logistics | 2018 |
| D Jones Contractors Limited | Construction | 2025 |
| D K New Homes Limited | Financial services | 2020 |
| D K Property Consultants Limited | Professional & scientific | 2025 |
| D Main Groundworks Ltd | Construction | 2024 |
| D P Maree Limited | Professional & scientific | 2014 |
| D P S Auto Services Limited | Wholesale & retail | 1998 |
| D&T Electronics (London) Limited | Construction | 2010 |
| D'Agostino Consulting Ltd | Professional & scientific | 2023 |
| D. Goodwin & Sons | Agriculture & fishing | 1996 |
| D. Nicholls ARB Limited | Administrative & support | 2020 |
| D.Jones Electrical & Maintenance Services Ltd | Construction | 2021 |
| D.Jones Electrical Services Ltd | Construction | 2022 |
| D.Jones Maintenance Services Ltd | Construction | 2022 |
| DA Silva Consulting Limited | Administrative & support | 2018 |
| Daaag Farming LLP | | 2024 |
| Dacorar (Crawley) Ltd | Real estate | 2024 |
| Dacorar (Southern) Limited | Construction | 2003 |
| Dacorar Limited | Real estate | 1996 |
| Dahl Developments Ltd | Construction | 2023 |
| Dale Aviation Limited | Transport & logistics | 2006 |
| Dame Jenny Harries Ltd | Professional & scientific | 2026 |
| Dami and EM Design Ltd | Wholesale & retail | 2023 |
| DAN Swain Limited | Financial services | 2024 |
| Danewood Press Limited (the) | Manufacturing | 1970 |
| Daniell & Daniell Ltd | Real estate | 2026 |
| Danish Living (Charing Cottage) Ltd | Real estate | 2025 |
| Danish Living (Hillside) Limited | Real estate | 2023 |
| Darbin-Hall Ltd | Professional & scientific | 2016 |
| Dark Water Consulting Ltd | Professional & scientific | 2021 |
| Dash Data LAB Ltd | Information & communication | 2025 |
| Data Research International Ltd | Professional & scientific | 2023 |
| Data ZIP Limited | Professional & scientific | 2023 |
| Dataprimate Ltd | Information & communication | 2017 |
| Dating Apps Must DIE Ltd | Administrative & support | 2023 |
| Datum Architects Limited | Professional & scientific | 2023 |
| Daughter of Croft Limited | Information & communication | 2020 |
| David Badock Design Limited | Professional & scientific | 2014 |
| David Fenner Ltd | Agriculture & fishing | 2014 |
| David James Consulting Ltd | Information & communication | 2017 |
| David Jenkins Design Limited | Professional & scientific | 2012 |
| Dawca Limited | Information & communication | 2024 |
| Dawnies Ltd | Wholesale & retail | 2018 |