| Cindy Clark Ltd | Health & social care | 2016 |
| Cineview Ltd | Information & communication | 2019 |
| Cinnamon Homes Limited | Real estate | 2018 |
| CIO Logistic Ltd | Transport & logistics | 2025 |
| CIP Handyman Limited | Construction | 2016 |
| Cipher Limited | Information & communication | 2006 |
| Cirac Engineering Limited | Manufacturing | 1983 |
| Circle Cloud Communications Ltd | Information & communication | 2015 |
| Circle Events Ltd | Hospitality | 2023 |
| Circle Guest House Ltd | Real estate | 2018 |
| Circle Parking Southampton Ltd | Transport & logistics | 2026 |
| Circle Technology Group Ltd | Information & communication | 2025 |
| Circleeasy Limited | Professional & scientific | 1997 |
| Circlenet LLP | | 2015 |
| Circona Limited | Administrative & support | 1995 |
| Circuit Hype Electrical Ltd | Construction | 2022 |
| Circuit Plus Electromechanicalcontracting Ltd | Construction | 2024 |
| Circumferential Motor Company Limited | Professional & scientific | 2018 |
| Cirlter Ltd | Wholesale & retail | 2023 |
| Citadel Civil Engineering Consultancy Ltd | Construction | 2015 |
| Citando Limited | Professional & scientific | 2008 |
| Citi Housing Group Limited | Real estate | 2024 |
| Citreas Life Ltd | Professional & scientific | 2019 |
| Citrine Estates Ltd | Real estate | 2024 |
| Citrus Lettings Limited | Real estate | 2020 |
| City & Abbey Chiropractic Limited | Health & social care | 2005 |
| City and Solent Properties Ltd | Real estate | 2025 |
| City Carpet Solutions Ltd | Wholesale & retail | 2026 |
| City Catering Southampton | Hospitality | 2014 |
| City Construction & Maintenance Limited | Construction | 2000 |
| City Domestics Limited | Other services | 1999 |
| City Estates Ltd | Real estate | 2024 |
| City EYE Limited | Information & communication | 1993 |
| City Glass Ltd. | Construction | 1999 |
| City Lettings (Southampton) Limited | Real estate | 2019 |
| City Life Church Southampton | Other services | 2003 |
| City Park Guest House Limited | Hospitality | 2002 |
| City Plumbing & Heating Southern Ltd | Construction | 2021 |
| City Road Lido Limited | Construction | 2019 |
| City Taxis 24/7 Ltd | Transport & logistics | 2024 |
| City Taxis Winchester Limited | Transport & logistics | 2024 |
| City Wide Music Ltd | Wholesale & retail | 2021 |
| City Zoom Ltd | Transport & logistics | 2025 |
| Cityclaim Residents Management Limited | Households | 1987 |
| Citycruisetransport Ltd | Transport & logistics | 2024 |
| Cityrent Limited | Real estate | 2016 |
| Cityrock Global Ltd | Real estate | 2020 |
| Cityspace Media Ltd | Information & communication | 2012 |
| Cityvan Links Ltd | Transport & logistics | 2020 |
| Ciucu Ltd | Transport & logistics | 2019 |
| Civil Military Relations CIC | Professional & scientific | 2025 |
| Civil Society Forum Limited | Other services | 2011 |
| Ciya Enterprises Ltd | Hospitality | 2025 |
| CJ Health Policy Research and Consulting Ltd | Professional & scientific | 2025 |
| CJ Vehicle Transport Limited | Transport & logistics | 2015 |
| CJA Aesthetics Ltd | Health & social care | 2017 |
| CJA Lifestyle Ltd | Health & social care | 2019 |
| CJA Medical Ltd | Health & social care | 2018 |
| CJB Metal Works Ltd | Manufacturing | 2026 |
| CJC Labs Ltd | Manufacturing | 2015 |
| CJC Rails Ltd | Construction | 2021 |
| CJF Enterprises Limited | Real estate | 2026 |
| CJK Engineering Limited | Manufacturing | 2014 |
| CJM Technical Recruitment Limited | Administrative & support | 2013 |
| CJN Law Limited | Professional & scientific | 2025 |
| CJR Consultancy Servces Limited | Professional & scientific | 2025 |
| CJR Propulsion Holdings Limited | Financial services | 2022 |
| CJR Propulsion Limited | Manufacturing | 1990 |
| CJR Real Estate Limited | Real estate | 2023 |
| CJS Recruit Ltd | Administrative & support | 2021 |
| CJT ROV Services Ltd | Professional & scientific | 2014 |
| Cjtv Limited | Information & communication | 2023 |
| CJW Spray Ltd | Manufacturing | 2017 |
| Cjwg Associates Limited | Professional & scientific | 2001 |
| CK & W Ltd | Professional & scientific | 2017 |
| CK Nationswide Ltd | Construction | 2024 |
| CKC Property Services Limited | Real estate | 2016 |
| Ckcarter Limited | Real estate | 2024 |
| CKR Legal Limited | Professional & scientific | 2021 |
| CKS Carpentry Ltd | Construction | 2018 |
| CKS Investment Properties Limited | Real estate | 2017 |
| CL Building Contractors Ltd | Construction | 2023 |
| CL Tech UK Limited | Professional & scientific | 2013 |
| Cl-Av Productions Limited | Arts & recreation | 2025 |
| Claddagh Commercial Management Limited | Construction | 2012 |
| Claire Aikman Limited | Administrative & support | 2023 |
| Claire Marie Hair Studio Ltd | Other services | 2026 |
| Claire's Dog Care Ltd | Other services | 2022 |
| Claire's Pilates Ltd | Information & communication | 2024 |
| Claire-Estelle Ltd | Manufacturing | 2024 |
| Clairelogic Corporate Ltd | Information & communication | 2011 |
| Clamel Limited | Health & social care | 2019 |
| Clantect Limited | Manufacturing | 2016 |
| Clare Packer Hair Ltd | Other services | 2023 |
| Claredale Finance Limited | Extraterritorial | 1981 |
| Clarence Blake & Sons Limited | Financial services | 2023 |
| Clarence Wharf Ltd | Hospitality | 2025 |
| Clarenden Communications Limited | Information & communication | 2024 |
| Clarenden Group Limited | Information & communication | 2021 |
| Clarges Street Mayfair Limited | Real estate | 2022 |