| Citylink Properties (UK) Ltd | Real estate | 2006 |
| Ciuby Transport Ltd | Transport & logistics | 2016 |
| Ciuciucm Ltd | Transport & logistics | 2024 |
| Civaxis Solutions Limited | Professional & scientific | 2025 |
| Civic&Co Ltd | Transport & logistics | 2019 |
| Civiconterra Consulting Group Ltd | Construction | 2025 |
| CJ Bookkeeping Solutions Ltd | Professional & scientific | 2022 |
| CJ Signature Homes Ltd | Construction | 2025 |
| CJB Plant Hire & Sales Ltd | Construction | 2026 |
| CJS (UK Management) Limited | Other services | 2004 |
| CJS Events UK Ltd | Financial services | 2023 |
| CJS Jewlery Ltd | Wholesale & retail | 2024 |
| CJS Lifestyle Ltd | Professional & scientific | 2021 |
| CK Agencies Limited | Wholesale & retail | 2012 |
| CK Direct Group Limited | Extraterritorial | 2016 |
| CK Elite Limited | Real estate | 2025 |
| Ck-Tech Ltd | Construction | 2013 |
| CKH Developments Limited | Hospitality | 2007 |
| CKN Norfolk Street Limited | Construction | 2022 |
| CKS Group Ltd | Administrative & support | 2016 |
| Ckss Properties Investments Ltd | Real estate | 2024 |
| CL Housing Services Ltd | Real estate | 2025 |
| Cladding Expert Ltd | Construction | 2023 |
| Cladfen Ltd | Administrative & support | 2020 |
| Clafh Healthcare Services Ltd | Administrative & support | 2019 |
| Claimify Limited | Professional & scientific | 2022 |
| Claire Boyes Creator Ltd | Wholesale & retail | 2026 |
| Claire Howlett Holdings Ltd | Hospitality | 2025 |
| Clare Folgate Limited | Professional & scientific | 2012 |
| Clare House Physiotherapy Limited | Health & social care | 2007 |
| Clarence Car Sales Ltd | Wholesale & retail | 2021 |
| Claridge Estates Limited | Real estate | 2007 |
| Clarifi Limited | Professional & scientific | 2017 |
| Clarity Fire Engineering Ltd | Professional & scientific | 2024 |
| Clarity Network Systems Limited | Professional & scientific | 1997 |
| Clark & Clark Developments Ltd | Construction | 2024 |
| Clark & Clark Holdings Ltd | Financial services | 2024 |
| Clark & Clark Houses Ltd | Real estate | 2023 |
| Clark Surveys Ltd | Professional & scientific | 2008 |
| Clark-Drain Limited | Manufacturing | 1978 |
| Clarke Construction Solutions LLP | | 2025 |
| Clarke Homes Ltd | Real estate | 2013 |
| Clarks Elite Heating Ltd | Construction | 2024 |
| Clarksteel Galvanising Limited | Professional & scientific | 1988 |
| Clarksteel Holdings Limited | Manufacturing | 1971 |
| Clarksteel Limited | Professional & scientific | 2004 |
| Class 1 Haulage Services Limited | Transport & logistics | 2019 |
| Class Foods Limited | Wholesale & retail | 2017 |
| CLASS1DRIVER Services Limited | Administrative & support | 2015 |
| Classic Fireplaces Limited | Construction | 2015 |
| Classic Network Solutions Ltd | Financial services | 2003 |
| Classic Printers (Crowland) Ltd | Manufacturing | 2016 |
| Classic Things Ltd | Wholesale & retail | 2024 |
| Classtuga Ltd | Health & social care | 2023 |
| Claudion Trans Ltd | Transport & logistics | 2014 |
| Claudiu Denisa Transport Ltd | Transport & logistics | 2025 |
| Clauscarsaleandrecovery Limited | Water & waste | 2025 |
| Clay Core Ltd | Information & communication | 2025 |
| Claypack Limited | Manufacturing | 1971 |
| Claytav Limited | Health & social care | 2026 |
| CLC Andaya Dragon Care Ltd | Health & social care | 2015 |
| CLC Repairs Ltd | Wholesale & retail | 2022 |
| CLD Contractors Limited | Construction | 1993 |
| Clean IT Cleaning Services Ltd | Administrative & support | 2019 |
| Clean+Care Ltd | Administrative & support | 2024 |
| Cleanbuild Services Ltd | Administrative & support | 2025 |
| Cleaning Peterborough Ltd | Administrative & support | 2022 |
| Cleaning Queen Franchise Ltd | Professional & scientific | 2024 |
| Cleaning Queen Ltd | Administrative & support | 2019 |
| Cleaning Residence Ltd | Administrative & support | 2019 |
| Cleanslate Tech Limited | Information & communication | 2026 |
| Cleantime Services Limited | Other services | 2006 |
| Clear Gold Recycling Limited | Professional & scientific | 2025 |
| Clear Signal Digital Ltd | Professional & scientific | 2026 |
| Clear Space Removals Ltd | Water & waste | 2025 |
| Clear Waters Sports Vision Ltd | Education | 2023 |
| Clearest Minds Limited | Health & social care | 2026 |
| Clearmove Furniture & Removals Ltd | Transport & logistics | 2026 |
| Clearview Fire Limited | Manufacturing | 2020 |
| Clearview Glaziers Company Limited | Construction | 2005 |
| Clearview Space Limited | Real estate | 2020 |
| Clearvision Home (Peterborough) Limited | Construction | 2022 |
| Clearvo Limited | Transport & logistics | 2026 |
| Cleave Fine Art Limited | Arts & recreation | 2009 |
| Cleaver Court Property Company Limited | Households | 1998 |
| Cleaver Enterprises Ltd | Hospitality | 2021 |
| Clements Financial Ltd | Financial services | 2018 |
| Clemglory Limited | Health & social care | 2024 |
| Cleracs Consulting Ltd | Professional & scientific | 2024 |
| Click Markets Ltd | Professional & scientific | 2014 |
| CLICK-4 (Midlands) Limited | | 2008 |
| CLICK2PRINT Ltd | Manufacturing | 2025 |
| Clicksuperstore Limited | Wholesale & retail | 2014 |
| Client Affairs Company Limited | Administrative & support | 2014 |
| Clientzone Limited | Administrative & support | 2007 |
| Climate Change Holdings Limited | Financial services | 2002 |
| Climate Cooling Solutions Ltd | Construction | 2007 |
| Climbwise AI Limited | Information & communication | 2025 |
| Clinch Coffee Ltd | Manufacturing | 2025 |
| Clinical Co-Ordinates Ltd | Health & social care | 2022 |