| Class Catering Ltd | Hospitality | 2024 |
| Class Divide Limited | Education | 2024 |
| Class Tours Limited | Transport & logistics | 2008 |
| Classic Co Design Ltd | Real estate | 2021 |
| Classic Design Interiors Limited | Wholesale & retail | 2012 |
| Classic Design Properties Ltd | Real estate | 2025 |
| Classic Jewellery Limited | Wholesale & retail | 1997 |
| Classic Mustangs UK Limited | Wholesale & retail | 2018 |
| Classic Revive and Drive Ltd | Extraterritorial | 2024 |
| Claudine Ickeringill Limited | Real estate | 2009 |
| Clavicorn Limited | Information & communication | 2002 |
| Clay Co Inc Ltd | Information & communication | 2021 |
| Clayfields Management Company Limited | Households | 1990 |
| CLB &Co.Events Ltd | Professional & scientific | 2025 |
| CLD BTN Limited | Hospitality | 2025 |
| Clean & Cleared Ltd | Administrative & support | 2026 |
| Clean Cold Power UK Limited | Professional & scientific | 2019 |
| Clean Wipes (Brighton) Limited | Wholesale & retail | 2023 |
| Cleanfx Ltd | Administrative & support | 2014 |
| Cleanroom & Containment Qualification Ltd | Professional & scientific | 2023 |
| Clear and Clean (Sussex) Ltd | Water & waste | 2025 |
| Clear Care Solutions Midco Limited | Financial services | 2025 |
| Clear Course Coaching Ltd | Administrative & support | 2026 |
| Clear Edge Property Solutions Ltd | Real estate | 2024 |
| Clear Horizons Limited | Education | 2024 |
| Clear Ocean Ltd | Hospitality | 2011 |
| Clear Shapes Digital Limited | Financial services | 2024 |
| Clearblack Ltd | Professional & scientific | 2025 |
| Clearbridge Tutors Ltd | Education | 2026 |
| Clearer Picture Limited | Construction | 2017 |
| Clearleft Limited | Information & communication | 2005 |
| Clearleft Trustees Limited | Administrative & support | 2020 |
| Clearline Recruitment Ltd | Administrative & support | 2017 |
| Clearly Clean Solutions Ltd | Administrative & support | 2025 |
| Clearpak Limited | Professional & scientific | 2010 |
| Clearsum Accounting Ltd | Professional & scientific | 2024 |
| Clearwest Limited | Agriculture & fishing | 1979 |
| Cleo and Co UK Limited | Professional & scientific | 2020 |
| Cleopatra Cosmetics Limited | Administrative & support | 1989 |
| Cleopatra International Limited | Extraterritorial | 2002 |
| Clerks Acre Phase II Ltd | Households | 2004 |
| Clerkyai Ltd | Information & communication | 2025 |
| Clermont Holdings Limited | Administrative & support | 2018 |
| Clever Cookie Ltd | Manufacturing | 2016 |
| Clever Girl Limited | Professional & scientific | 2022 |
| Cleverfox Ltd | Information & communication | 2023 |
| Clevernest Property Group Ltd | Real estate | 2023 |
| Cleverwave LLP | | 2025 |
| Clevry UK Ltd | Information & communication | 1997 |
| Click Click Bang Limited | Wholesale & retail | 2014 |
| Clickafloor Limited | Construction | 2023 |
| Clickahead Marketing Limited | Information & communication | 2023 |
| Clickcart Solutions Ltd | Wholesale & retail | 2021 |
| Cliff Plumbing and Heating Limited | Construction | 2016 |
| Cliffe Property Group Limited | Real estate | 2012 |
| Cliffe Property Holdings Limited | Real estate | 2020 |
| Clifford Baines International Limited | Administrative & support | 2009 |
| Cliffside Properties Limited | Real estate | 2005 |
| Clifton Bros. (Concrete) Limited | Wholesale & retail | 1989 |
| Clifton Hill Ltd | Administrative & support | 2017 |
| Clifton House Hotels Limited | Hospitality | 2024 |
| Clifton Lodge Residents Association Limited | Households | 2008 |
| Cliftonville Holistics Limited | Health & social care | 2024 |
| Climate Impact Advisors Limited | Professional & scientific | 2026 |
| Clinic 55 Limited | Health & social care | 2020 |
| Clinical Vantage Limited | Education | 2016 |
| Clinorabookings Ltd | Professional & scientific | 2025 |
| Clive Hawkins Architects Ltd | Professional & scientific | 2007 |
| Clive Ltd | Information & communication | 2024 |
| Clive Seabrook Limited | Professional & scientific | 1997 |
| Clive Sefton Limited | Arts & recreation | 2012 |
| Clivecourt Building Ltd | Real estate | 2025 |
| Clock Tower PUB Company Ltd | Hospitality | 2025 |
| Close to the Stone Limited | Professional & scientific | 2021 |
| Closer Work Americas Ltd | Financial services | 2025 |
| Closer World Ltd | Financial services | 2025 |
| Closs and Hamblin Chichester Ltd | Wholesale & retail | 2019 |
| Closs and Hamblin Winchester Ltd | Wholesale & retail | 2019 |
| Cloth Control Ltd | Wholesale & retail | 2021 |
| Cloud 10 Brighton Limited | Professional & scientific | 2024 |
| Cloud 4 Sure Ltd | Information & communication | 2017 |
| Cloud 9 Leisure Limited | Arts & recreation | 2017 |
| Cloud Edits Ltd | Information & communication | 2012 |
| Cloud Fundamental Ltd | Information & communication | 2015 |
| Cloud Heating Ltd | Construction | 2023 |
| Cloud Sports Management UK Ltd | Arts & recreation | 2017 |
| Cloudberry I Carry LLP | | 2025 |
| Cloudberry I GP LLP | | 2025 |
| Cloudberry I LP | | 2025 |
| Cloudbursts AI Ltd | Information & communication | 2025 |
| Cloudperfect Ltd | Information & communication | 2010 |
| Clpsychology Ltd | Professional & scientific | 2025 |
| CLR Media Limited | Information & communication | 2020 |
| CLT Connections Ltd | Construction | 2023 |
| CLT Structures LLP | | 2008 |
| Cltch Ltd | Professional & scientific | 2023 |
| Club Class Insurance Services Limited | Financial services | 2003 |
| Club Culture Brighton Ltd | Other services | 2017 |
| Clubhouse Mobile Mini Golf Global Ltd | Financial services | 2022 |
| Clubhouse@Bmyc Ltd | Hospitality | 2023 |