| Conrad Energy (Nominee) II Limited | Financial services | 2021 |
| Conrad Energy (O&M) Limited | Administrative & support | 2020 |
| Conrad Energy (Property) II Limited | Real estate | 2020 |
| Conrad Energy (Property) Limited | Real estate | 2017 |
| Conrad Energy (Solar Developments) Limited | Energy | 2022 |
| Conrad Energy (Solar Operations) Limited | Energy | 2023 |
| Conrad Energy (Trading) Limited | Energy | 2017 |
| Conrad Energy Group II Limited | Financial services | 2020 |
| Conrad Energy Group Limited | Financial services | 2017 |
| Conrad Energy Limited | Energy | 2015 |
| Conrad Lytham (Holdings) Limited | Energy | 2015 |
| Consentium Limited | Real estate | 2008 |
| Contracting Made Simple Ltd | Professional & scientific | 2023 |
| Contracts Made Simple Ltd | Professional & scientific | 2023 |
| Cool Canines Oxford Ltd | Agriculture & fishing | 2019 |
| Cooldown Clothing Ltd | Wholesale & retail | 2019 |
| Coombes Home Improvements Limited | Construction | 2022 |
| Coombes Land and Development Limited | Professional & scientific | 2018 |
| Cooper Dryden Limited | Construction | 2013 |
| Copier Supplies Limited | Other services | 2010 |
| Copy Right Systems Limited | Other services | 1996 |
| Coralle Unlimited Limited | Professional & scientific | 2019 |
| Corkers Farm Partnership Limited | Agriculture & fishing | 1995 |
| Cormack Consulting Ltd | Professional & scientific | 2026 |
| Corne Motors Ltd | Wholesale & retail | 2015 |
| Cornerstroke Ltd | Professional & scientific | 2013 |
| Corneville Consulting Limited | Professional & scientific | 2012 |
| Corporate Build UK Ltd | Construction | 2019 |
| Corporate Minds Consultancy Limited | Health & social care | 2018 |
| Corrig Consulting Ltd | Professional & scientific | 2020 |
| Corrigan Heating Services Limited | Construction | 2019 |
| Cortex Coaching Ltd | Professional & scientific | 2026 |
| Cosec Smart Limited | Administrative & support | 2012 |
| Coshe Juices Ltd | Manufacturing | 2024 |
| Cosmic Ventures Group Ltd | Wholesale & retail | 2026 |
| Cosmology Limited | Hospitality | 2020 |
| Costwold Granite & Marble Ltd | Mining & quarrying | 2017 |
| Cothill Farms Oxfordshire Limited | Construction | 2016 |
| Cothill PIT Limited | Construction | 2016 |
| Cotsdale Consulting Ltd | Administrative & support | 2023 |
| Cotswold Off-Road Ltd | Wholesale & retail | 2023 |
| Count 4 YOU Ltd | Administrative & support | 2017 |
| Countryside Building Co Limited | Construction | 2017 |
| County Wedding Suppliers UK Limited | Professional & scientific | 2025 |
| Court Management Company Limited(The) | Households | 1985 |
| Couva Limited | Manufacturing | 2011 |
| Covenant Healthcare Services Limited | Health & social care | 2020 |
| Coys Materials Ltd | Other services | 2024 |
| Cozart Limited | Manufacturing | 2004 |
| CPC Resources Ltd | Health & social care | 2023 |
| CPL Business Consultants Limited | Professional & scientific | 2020 |
| CPL Executive Search Limited | Extraterritorial | 2020 |
| CPL Scientific Group Limited | Professional & scientific | 2014 |
| CPL Scientific Limited | Professional & scientific | 2022 |
| Crafty Pugs Limited | Wholesale & retail | 2025 |
| Cranbourne (Weymouth) Limited | Construction | 2015 |
| Cranbourne Enterprises Ltd | Administrative & support | 2009 |
| Cranbourne Homes Limited | Construction | 2012 |
| Crayfer JOE Limited | Construction | 2023 |
| Crayfish Rowing Ltd | Manufacturing | 2025 |
| Creatorax Solutions Ltd | Wholesale & retail | 2025 |
| Cree Security Limited | Administrative & support | 2023 |
| Creps and Clothes Limited | Wholesale & retail | 2020 |
| CRH Carpentry & Building Limited | Construction | 2019 |
| Cricket Accountants Ltd | Professional & scientific | 1999 |
| Cricket Annuitants | Administrative & support | 2010 |
| Cricket Connections Global Ltd | Arts & recreation | 2024 |
| Criptic-Arvis Limited | Manufacturing | 1981 |
| Crisfield Educational Consultancy Limited | Education | 2021 |
| Crispin Orthotics Ltd | Manufacturing | 2003 |
| Criterium Consulting Limited | Administrative & support | 2013 |
| CRM Transformation Limited | Professional & scientific | 2015 |
| Croftings Ltd | Real estate | 2019 |
| Crossland EOT Limited | Administrative & support | 2020 |
| Crossland Solicitors Ltd | Professional & scientific | 2010 |
| Crowcon Detection Instruments Limited | Manufacturing | 1970 |
| Crown Motorway Ltd | Wholesale & retail | 2021 |
| Crystal 2021 Limited | Administrative & support | 2021 |
| Crystal Clear Marketing Limited | Manufacturing | 2012 |
| Crystalox Limited | Manufacturing | 1994 |
| Crystalox Solar Limited | Professional & scientific | 1994 |
| CSD Training Limited | Administrative & support | 2009 |
| Csez Ltd | Hospitality | 2025 |
| CSH Digital Ltd | Information & communication | 2025 |
| CSS Touring Ltd | Arts & recreation | 2023 |
| CTH Consulting Limited | Extraterritorial | 2007 |
| Ctrl Music Limited | Arts & recreation | 2018 |
| Culham Prints and Drawings Limited | Wholesale & retail | 1976 |
| Cunningham Asquith Projects Ltd | Construction | 2015 |
| Curtis Research Ltd | Information & communication | 2012 |
| Curve Medical Limited | Professional & scientific | 2012 |
| CVJ Investments Ltd | Real estate | 2020 |
| Cw&St PUB Co Limited | Hospitality | 2025 |
| CY4UDEV Limited | Wholesale & retail | 2024 |
| Cyber Simplexity Ltd | Professional & scientific | 2025 |
| CYD Cosmetics Ltd | Wholesale & retail | 2025 |
| Cydea Ltd | Professional & scientific | 2019 |
| Cygnus Ventures Ltd | Financial services | 2022 |
| Cyott Limited | Real estate | 2008 |
| Cyprotex Discovery Limited | Administrative & support | 2001 |