| Children's International Film Festival CIC | Education | 2025 |
| Chillvex Ltd | Manufacturing | 2026 |
| Chiltern Manor Limited | Real estate | 2021 |
| Chimmys Ltd | Manufacturing | 2018 |
| Chiswick Aesthetics House Ltd | Health & social care | 2026 |
| Chloe & IAN Limited | Real estate | 2019 |
| Chloe Storey Management Ltd | Administrative & support | 2022 |
| Choasia Limited | Hospitality | 2025 |
| Choclab Ltd | Administrative & support | 2022 |
| Choise Ltd | Professional & scientific | 2019 |
| Choose 2 Rent UK Ltd | Administrative & support | 2022 |
| Chris George Ltd | Wholesale & retail | 2021 |
| Christian DJ Installations Ltd | Manufacturing | 2026 |
| Christian Waibel Ltd | Professional & scientific | 2024 |
| Chrysalis Partners Business Consulting Ltd | Professional & scientific | 2021 |
| Chrystal Care Ltd | Transport & logistics | 2025 |
| CI Recruitment Ltd | Administrative & support | 2026 |
| Cinapsis Limited | Information & communication | 2018 |
| Cincom Design & Build Ltd | Construction | 2023 |
| Cincom Mokotech UK Limited | Manufacturing | 2023 |
| Cine-Uk Limited | Information & communication | 1995 |
| Cinema Paradiso Property Ltd | Real estate | 2020 |
| Cineworld Cinema Properties Limited | Extraterritorial | 1932 |
| Cineworld Cinemas Holdings Limited | Professional & scientific | 1986 |
| Cineworld Cinemas Limited | Information & communication | 1985 |
| Cineworld Elite Picture Theatre (Nottingham) Limited | Extraterritorial | 1919 |
| Cineworld Estates Limited | Administrative & support | 1990 |
| Cineworld Holdings Limited | Professional & scientific | 2004 |
| Cineworld South East Cinemas Limited | Extraterritorial | 1928 |
| Cinqd Ltd | Information & communication | 2023 |
| Ciortescu Air Fittings Ltd | Construction | 2026 |
| City Franchise Group Limited | Hospitality | 2024 |
| City Screen (Brighton) Limited | Information & communication | 1994 |
| City Screen (Liverpool) Limited | Information & communication | 2000 |
| City Screen (S.O.A.) Limited | Extraterritorial | 1995 |
| City Screen (Stratford) Limited | Information & communication | 1996 |
| City Screen (York) Limited | Information & communication | 1997 |
| Citycom Technologies Group Limited | Financial services | 2013 |
| Citycom Technologies Ltd | Administrative & support | 2012 |
| Civitem Services Limited | Information & communication | 2022 |
| CJ and Company Limited | Professional & scientific | 2013 |
| CK Design Lighting Ltd | Professional & scientific | 2020 |
| Ckraft Design and Build Ltd | Construction | 2020 |
| Clad Design Resource Limited | Construction | 2010 |
| Claimspec Limited | Professional & scientific | 2005 |
| Clan Technical Consultants Limited | Professional & scientific | 2016 |
| Clarity One Ltd | Professional & scientific | 2003 |
| Clarke Agents (Europe) Limited | Professional & scientific | 2012 |
| Claryon Systems Ltd | Information & communication | 2018 |
| Class 7 Ltd | Wholesale & retail | 2025 |
| Classic Cinemas Limited | Information & communication | 1995 |
| Classic Fit Ltd | Other services | 2025 |
| Cleanerplus Limited | Administrative & support | 2025 |
| Clear Visual Cleaning Ltd | Administrative & support | 2024 |
| Clearway Mobility Access Ltd | Wholesale & retail | 2025 |
| Clemency Ltd | Administrative & support | 2024 |
| Cleos Cloths Ltd | Manufacturing | 2024 |
| Cleos Garden Ltd | Agriculture & fishing | 2025 |
| Click Afro Beauty Limited | Wholesale & retail | 2025 |
| Click Floor Ltd | Construction | 2023 |
| Client Onboard TD Limited | Information & communication | 2026 |
| Clinical Lens CIC | Information & communication | 2026 |
| Closer Dreams Ltd | Information & communication | 2024 |
| Cloud Aware Services Ltd | Information & communication | 2022 |
| Cloud HUG by Sebastian Ltd | Wholesale & retail | 2026 |
| Cloudrev Ltd | Other services | 2014 |
| Clubq Limited | Health & social care | 2023 |
| Cluedin UK Ltd | Information & communication | 2021 |
| Clyra Ltd | Information & communication | 2026 |
| Clyvinco Estates Ltd | Real estate | 2026 |
| CMK Accounting Services Ltd | Professional & scientific | 2018 |
| CMR Servers Limited | Information & communication | 2020 |
| CNC International Trading Company Limited | Wholesale & retail | 2018 |
| Cockerel Engineering Services Limited | Professional & scientific | 2016 |
| Code&Ai Limited | Education | 2022 |
| Codegence Consulting Limited | Information & communication | 2019 |
| Codevia IT Services Limited | Information & communication | 2025 |
| Coffee Keenya Ltd | Wholesale & retail | 2022 |
| Cokix Consulting Ltd | Information & communication | 2020 |
| Cokix Group UK Ltd | Information & communication | 2020 |
| Cokolwiek Ltd | Transport & logistics | 2019 |
| Cold Wind Ltd | Construction | 2023 |
| Collective Trends UK Ltd | Information & communication | 2019 |
| Collins Salonna Ltd | Education | 2024 |
| Comakeit UK PVT Ltd | Information & communication | 2019 |
| Comet Films Ltd | Arts & recreation | 2017 |
| Commerce Forz Ltd | Information & communication | 2022 |
| Common-Editions Ltd | Information & communication | 2014 |
| Commsearch Recruitment Ltd | Administrative & support | 2023 |
| Companies in Italy Limited | Administrative & support | 2010 |
| Completed by Limited | Construction | 2021 |
| Comptech Ltd | Education | 2009 |
| Compugra Systems Inc Limited | Information & communication | 2025 |
| Coms Regulatory Consulting Limited | Professional & scientific | 2002 |
| Comtech Research Limited | Manufacturing | 2016 |
| Concept Fashion & Clothing Ltd | Wholesale & retail | 2016 |
| Concept Protection Ltd | Transport & logistics | 2013 |
| Confocal Diagnostic Laboratory Limited | Health & social care | 2024 |
| Connected Insight Europe Ltd | Information & communication | 2022 |
| Connecting Coins Ltd | Financial services | 2025 |