| Common Sense Compliance Limited | Professional & scientific | 2009 |
| Commonplace Collective Ltd | Professional & scientific | 2025 |
| Commuspace Ltd | Professional & scientific | 2019 |
| Companion Care (Ashton) Limited | Professional & scientific | 2001 |
| Companion Care (Ballymena) Limited | Professional & scientific | 2012 |
| Companion Care (Basingstoke) Limited | Professional & scientific | 2004 |
| Companion Care (Bolton) Limited | Professional & scientific | 2002 |
| Companion Care (Crayford) Limited | Professional & scientific | 2002 |
| Companion Care (Huddersfield) Limited | Professional & scientific | 2002 |
| Companion Care (Peterborough) Limited | Professional & scientific | 2002 |
| Companion Care (Poole) Limited | Professional & scientific | 2001 |
| Companion Care (Portsmouth) Limited | Professional & scientific | 2001 |
| Company Debt Solutions Online Limited | Other services | 2024 |
| Compass Property (Greater Manchester) Ltd | Real estate | 2015 |
| Complete Aesthetics Clinic Limited | Health & social care | 2017 |
| Complete Business Administration Ltd | Professional & scientific | 2026 |
| Complete Capital Allowances Ltd | Administrative & support | 2021 |
| Complete Industrial Cleaning Ltd | Water & waste | 2023 |
| Complete Pharmacovigilance Solutions Ltd | Professional & scientific | 2014 |
| Complete Spraying Solutions Limited | Construction | 2024 |
| Complheat Limited | Construction | 2014 |
| COMPLY360 Ltd | Professional & scientific | 2023 |
| COMPOUND22 Limited | Wholesale & retail | 2020 |
| Compulease Limited | Information & communication | 2000 |
| Computing Software Limited | Information & communication | 1994 |
| Concept House (Warrington) Limited | Real estate | 2015 |
| Concept Shape Limited | Professional & scientific | 2008 |
| Concept to Delivery Group Ltd | Administrative & support | 2020 |
| Concretene Limited | Professional & scientific | 2019 |
| Confident Communication Therapy Ltd | Health & social care | 2014 |
| Connect IT (Manchester) Limited | Information & communication | 2007 |
| Connected Installation Ltd | Construction | 2023 |
| Conquaero Limited | Financial services | 2001 |
| Conservative Drug Policy Reform Group Ltd | Professional & scientific | 2018 |
| Consigliere Advisory Ltd | Professional & scientific | 2011 |
| Construction and Training Limited | Construction | 2024 |
| Construction GR Ltd | Construction | 2025 |
| Constructive Interactions Ltd. | Professional & scientific | 2006 |
| Consultery Ltd | Information & communication | 2016 |
| Consulting Justice Ltd | Professional & scientific | 2025 |
| Contemporary Living Properties Limited | Real estate | 2003 |
| Content 10X Ltd | Professional & scientific | 2021 |
| Content HQ Studio Limited | Professional & scientific | 2024 |
| Contrado Capital Limited | Financial services | 2020 |
| Conurbia Limited | Construction | 1996 |
| Convex Corporate Finance Limited | Financial services | 2024 |
| Convorto Limited | Professional & scientific | 2016 |
| Coolshores Limited | Wholesale & retail | 2026 |
| Copeland Richardson Limited | Health & social care | 2015 |
| Copper Kennels Limited | Wholesale & retail | 2023 |
| Coral Admin Services Ltd | Information & communication | 2019 |
| Coral Technologies Limited | Information & communication | 2011 |
| Corcoran Chemicals Limited | Wholesale & retail | 1976 |
| Corcoran Products Limited | Wholesale & retail | 2012 |
| Core Four Consultancy Limited | Professional & scientific | 2026 |
| Core Precision Comms Limited | Information & communication | 2025 |
| Corkland Estates Limited | Real estate | 2024 |
| Corporate Consultancy Limited | Professional & scientific | 2021 |
| Corporate Cookery Ltd | Other services | 2016 |
| Cortical Holdings Ltd | Health & social care | 2017 |
| Cosmedic Clinic Limited | Health & social care | 2018 |
| Cosmetique Clinics Limited | Other services | 2000 |
| Costly Oak Limited | Financial services | 2025 |
| Cotswold Hand Surgery Ltd | Health & social care | 2024 |
| County Blending Solutions Ltd | Manufacturing | 2026 |
| County Farm Feeds Ltd | Manufacturing | 2026 |
| County Food Ingredients Ltd | Wholesale & retail | 2017 |
| County Milk Products Limited | Wholesale & retail | 1993 |
| Courtyard Homes Property Consultants Limited | Administrative & support | 2006 |
| Covesea Clinical Consulting Ltd | Health & social care | 2020 |
| CPC Payroll Management Servics Ltd Ltd | Hospitality | 2022 |
| CPR Design Services Limited | Manufacturing | 2012 |
| CR8OR Web Ltd | Information & communication | 2022 |
| Crabtree & Associates Ltd | Professional & scientific | 2018 |
| Cranfield Quinn Medical Limited | Health & social care | 2024 |
| Crathorne Homes Limited | Real estate | 2015 |
| Craven Consultancy Ltd | Professional & scientific | 2025 |
| CRC Design Services Ltd | Professional & scientific | 2023 |
| Crco Limited | Professional & scientific | 2025 |
| Create Centre Medical Service Limited | Health & social care | 2019 |
| Created by Hydro Limited | Information & communication | 2022 |
| Creating Beautiful Smiles Limited | Health & social care | 2017 |
| Creative 21 Ltd | Hospitality | 2022 |
| Creative Leisure Consultants Limited | Real estate | 2013 |
| Creative Leisure Properties LLP | | 2021 |
| Creative Wilderness Ltd | Professional & scientific | 2017 |
| Cretan Life Land Limited Partnership | | 2009 |
| Crewe Estates Limited | Real estate | 2025 |
| CRH Consulting Services Limited | Professional & scientific | 2024 |
| Crichton Hall Holdings Ltd | Construction | 2022 |
| Crittall Construction Limited | Professional & scientific | 1956 |
| Crittall-Hope Engineering Limited | Professional & scientific | 1949 |
| Crma (UK) Limited | Other services | 2019 |
| Crma (UK) Properties Limited | Real estate | 2023 |
| Croftside Tennis Club Limited | Arts & recreation | 2015 |
| Croma Marketing Limited | Professional & scientific | 2025 |
| Crompton Place Management Company Limited | Households | 2013 |
| Crown Clinic Limited | Health & social care | 2007 |
| Crown Hair Clinic Limited | Health & social care | 2021 |
| Crown Place (Management Company) Limited | Households | 2018 |