| Connaught Factsline Limited | Administrative & support | 1993 |
| Connect Intelligent Technologies Ltd | Information & communication | 2025 |
| Connection Goal Ltd | Information & communication | 2018 |
| Constructree Ltd | Information & communication | 2024 |
| Constructum Contracts Limited | Construction | 2024 |
| Consultailor Ltd | Professional & scientific | 2021 |
| Consultford Limited | Information & communication | 2024 |
| Consulting by NT Ltd | Professional & scientific | 2023 |
| Consulting Skill Ltd | Professional & scientific | 2017 |
| CONT3XT Limited | Manufacturing | 2007 |
| Contrologist Ltd | Manufacturing | 2024 |
| Convivium Photography Ltd | Information & communication | 2026 |
| Convoy Community Ltd | Professional & scientific | 2020 |
| Cooper Design & Build Limited | Construction | 2023 |
| Copper Express Ltd | Hospitality | 2025 |
| Corduroy Properties Limited | Real estate | 2022 |
| Core Construction Consultants Ltd | Construction | 2022 |
| Core Holding Limited | Real estate | 2020 |
| Corevita (UK) Ltd | Manufacturing | 2023 |
| Corporate Immigration Services Limited | Professional & scientific | 2012 |
| Corpus 7 Ltd | Information & communication | 2024 |
| Corsair Capital Partners Limited | Financial services | 2014 |
| Corse Media Services Limited | Professional & scientific | 2005 |
| Cortayne CRT. Freehold Limited | Households | 2026 |
| Corwin Store Ltd | Wholesale & retail | 2026 |
| Cosmicology Ltd | Education | 2025 |
| Cosmä Terra Limited | Professional & scientific | 2022 |
| Coss Consulting Ltd | Professional & scientific | 2026 |
| Costain Services Limited | Construction | 2015 |
| Cottage Close Properties Ltd | Real estate | 2018 |
| Country and Twee Limited | Wholesale & retail | 2012 |
| Country and Urban Limited | Construction | 2020 |
| County Carpentry and Joinery Ltd | Manufacturing | 2026 |
| Courtney Wylie Consulting Ltd | Information & communication | 2021 |
| Coutts and Mann Ltd | Administrative & support | 2021 |
| Covent and Brydges Limited | Financial services | 2023 |
| Covent Garden Nutraceuticals Ltd | Administrative & support | 2017 |
| CP Church Street & CPA Ltd | Real estate | 2012 |
| CP Homes and Properties Limited | Real estate | 2025 |
| CPC Heating Ltd | Construction | 2025 |
| CPR Financial LLP | | 2007 |
| CPT Formwork and Consultancies Services Limited | Construction | 2018 |
| Crafting Ltd | Information & communication | 2024 |
| Crane Valley Community Interest Company | Professional & scientific | 2021 |
| Craneford Ltd | Information & communication | 2025 |
| Cranleigh Food & Wine Limited | Wholesale & retail | 2012 |
| Crayson Limited | Administrative & support | 2010 |
| Crea Digital Services Limited | Information & communication | 2021 |
| Creatio Consultancy Services Ltd | Professional & scientific | 2020 |
| Creatio Limited | Information & communication | 2008 |
| Creatio Spark Limited | Information & communication | 2019 |
| Creative 4 Today Ltd | Information & communication | 2018 |
| Creative Spaces London CIC | Health & social care | 2019 |
| Creative Word London Ltd | Professional & scientific | 2014 |
| Creative Word PM Limited | Extraterritorial | 2016 |
| Cremp Ltd | Transport & logistics | 2013 |
| Creran Associates Ltd | Professional & scientific | 2021 |
| Crew Twickenham Ltd | Manufacturing | 2025 |
| Creyi Ltd | Information & communication | 2015 |
| Crimson Koala Ltd | Information & communication | 2023 |
| Cristal London Limited | Administrative & support | 2015 |
| Cristal Sandbanks Limited | Real estate | 2026 |
| Criticalpath Engineering Ltd | Professional & scientific | 2025 |
| Croft House (Preston) Ltd | Health & social care | 2014 |
| Cromwell Builders Limited | Construction | 2013 |
| Crossley Management Limited | Professional & scientific | 1993 |
| Crowded Productions Limited | Information & communication | 2018 |
| Crown Classic Cars Limited | Wholesale & retail | 1989 |
| Crown Cycles Limited | Other services | 2012 |
| Crown Drycleaners (Whitton) Limited | Other services | 1994 |
| Crowndelidz Limited | Hospitality | 2024 |
| Crusader Leisure Limited | Administrative & support | 1995 |
| Crust & Craft Pizza Ltd | Hospitality | 2023 |
| Cruthaigh Limited | Professional & scientific | 2021 |
| Crypticorp Limited | Financial services | 2026 |
| Cryptogenic Games Limited | Information & communication | 2024 |
| Crystal Cleaners Whitton Ltd | Other services | 2024 |
| Crystal Property Cleaning Ltd | Administrative & support | 2005 |
| Crèche My Party Ltd | Health & social care | 2021 |
| CS Building Consultants Ltd | Professional & scientific | 2024 |
| CS Holdings 2020 Ltd | Financial services | 2019 |
| CS Knight Properties Ltd | Real estate | 2022 |
| CSC Media Group Limited | Information & communication | 2026 |
| CSJ Risk Consulting Limited | Professional & scientific | 2017 |
| CT Marine Service & Software Ltd | Manufacturing | 2020 |
| Cubcare Limited | Health & social care | 2015 |
| Cube Financial Limited | Financial services | 2018 |
| Cura Care Group Limited | Health & social care | 2019 |
| Cura Care Limited | Health & social care | 2011 |
| Curley Leisure Limited | Real estate | 1992 |
| Current Cycles Creative Ltd | Manufacturing | 2018 |
| Currie Motors Holding Company Limited | Real estate | 2026 |
| Cursedcollection Ltd | Wholesale & retail | 2025 |
| Cusp Consultancy Ltd | Professional & scientific | 2022 |
| Custom Construct Limited | Construction | 2017 |
| Custom Green Limited | Administrative & support | 2016 |
| CUTH99 Ltd | Professional & scientific | 2019 |
| Cutis Skin Technologies Limited | Wholesale & retail | 2021 |
| Cutover Consulting Limited | Information & communication | 2017 |
| Cutters Limited | Wholesale & retail | 2006 |