| Club Radio Ltd | Arts & recreation | 2023 |
| Club Salami Limited | Manufacturing | 2026 |
| CM Aero Consultancy Ltd | Professional & scientific | 2022 |
| CM Lifecycle Finance Ltd | Financial services | 2019 |
| Cmart Roofing Ltd | Construction | 2024 |
| CMD Technology Ltd | Information & communication | 2019 |
| CMP Holdings Limited | Financial services | 2020 |
| CMV Property Limited | Real estate | 2018 |
| Coachindepth Limited | Professional & scientific | 2017 |
| Coaching at Work Limited | Information & communication | 2009 |
| Coaching With Wine Ltd | Professional & scientific | 2012 |
| Coachworx Consulting Ltd | Wholesale & retail | 2008 |
| Coachworx Holdings Limited | Wholesale & retail | 2019 |
| Coady Fleet Risk Management Ltd | Education | 2019 |
| Coast & Country Estates Ltd | Real estate | 2025 |
| Cocojo Properties Limited | Real estate | 2025 |
| Coda Falconry Ltd | Education | 2020 |
| Codebrew Limited | Information & communication | 2014 |
| Codicote Finance Limited | Financial services | 2005 |
| Coffee & Pink Ltd | Other services | 2004 |
| Colby Consultancy Ltd | Construction | 2019 |
| Colebourn & Gray Ltd | Real estate | 2020 |
| Colin Hemmings Limited | Real estate | 2006 |
| Colin Hill Bar & Catering Supplies Ltd | Wholesale & retail | 1999 |
| Colin Hill Building Solutions Ltd | Construction | 2012 |
| Colour Story Ltd | Wholesale & retail | 2022 |
| Colville Hall Events Limited | Hospitality | 2019 |
| Colwells Enterprises Limited | Manufacturing | 1989 |
| Comfort Furs Ltd | Wholesale & retail | 2021 |
| Cominco Resources (UK) Limited | Mining & quarrying | 2010 |
| Commercial Fire Protection Ltd | Construction | 2021 |
| Commercial Fire Protection UK Ltd | Construction | 2021 |
| Commercial Services Property Limited | Real estate | 2024 |
| Commercial Services UK Ltd | Administrative & support | 2008 |
| Common Ground Editorial Limited | Information & communication | 2026 |
| Commonwealth Music International Limited | Arts & recreation | 2019 |
| Commonwealth Youth Orchestra and Choir | Arts & recreation | 2011 |
| Commotion Digital Ltd | Professional & scientific | 2024 |
| Communication, Speech and Language Therapy Limited | Education | 2025 |
| Compass Guide Ltd | Professional & scientific | 2024 |
| Composite Machining Services Ltd | Manufacturing | 2015 |
| Concinnity IT Services Ltd | Information & communication | 2019 |
| Confluence (UK) Limited | Education | 2014 |
| Confluence Sustainability Limited | Professional & scientific | 2014 |
| Conifer Comedy Limited | Arts & recreation | 2015 |
| Connaught Clinical Consulting Limited | Information & communication | 2009 |
| Connect Networks LLP | | 2003 |
| Connect Sales Services Ltd | Professional & scientific | 2024 |
| Connor MAY Investments Ltd | Real estate | 2016 |
| Connor Walters Estate Agents Ltd | Real estate | 2021 |
| Considered Therapy Ltd | Health & social care | 2025 |
| Consilium Financial Planning Limited | Financial services | 2001 |
| Constant Studio Ltd | Information & communication | 2025 |
| Construct Analytics Ltd | Professional & scientific | 2026 |
| Constructing London Ltd | Construction | 2017 |
| Constructive Works Limited | Manufacturing | 2020 |
| Consult AG Ltd | Professional & scientific | 2023 |
| Consultantnet Ltd | Professional & scientific | 2003 |
| Continentally Limited | Financial services | 2025 |
| Contour Creative Studio Limited | Professional & scientific | 2017 |
| Controversy Limited | Other services | 2015 |
| Convergent Intelligentia Limited | Education | 2015 |
| Conway Investments Limited | Real estate | 1984 |
| Cookers Corner Management Company Limited | Households | 2022 |
| Coomy Holdings Limited | Financial services | 2018 |
| Cooper and Westlake Limited | Professional & scientific | 2015 |
| Cooper Consumer Health UK Limited | Wholesale & retail | 2023 |
| Cooper Family Partnership LLP | | 2022 |
| Cooper Homes (Letchworth) Limited | Real estate | 2017 |
| Cooper Stunts Ltd | Arts & recreation | 2015 |
| Cooperx Property Limited | Real estate | 2018 |
| Copper Box Events Ltd | Hospitality | 2022 |
| Copperleaf Wills Ltd | Professional & scientific | 2023 |
| COR Solutions Services Limited | Information & communication | 2023 |
| Core Spring Group Limited | Financial services | 2026 |
| Core Spring Home Limited | Health & social care | 2026 |
| Core Spring Properties Limited | Real estate | 2026 |
| Coregrid Engineering Ltd | Construction | 2025 |
| Corn Hill Therapeutic Interventions CIC | Health & social care | 2026 |
| Cornerstone Assurance Ltd | Professional & scientific | 2026 |
| Cornerstone Consulting Engineers Limited | Professional & scientific | 2002 |
| Cornerways Care Ltd | Health & social care | 2014 |
| Cornerways Homes Ltd | Health & social care | 2022 |
| Cornerways Properties Ltd | Real estate | 2019 |
| Cornhill Alpacas Limited | Agriculture & fishing | 2025 |
| Corporate Women's Health Ltd | Health & social care | 2025 |
| Corporatec (UK) Limited | Information & communication | 2013 |
| Corylus Medical Ltd | Professional & scientific | 2020 |
| Cosilium Limited | Construction | 2022 |
| Costdeal Limited | Construction | 1994 |
| Cotech Consult Limited | Information & communication | 2017 |
| Cotswold Property Group Limited | Real estate | 2016 |
| Cotton Engineering Ltd | Professional & scientific | 2018 |
| Coughlin Dean Limited | Professional & scientific | 2020 |
| Coull Runnings Ltd | Professional & scientific | 2026 |
| Coulson Moore Renovation Ltd | Construction | 2016 |
| Country Fair & Dog Show Limited | Other services | 2025 |
| Countrywide S E G M Ltd | Agriculture & fishing | 2019 |
| County Grounds Services Ltd | Administrative & support | 2013 |
| Court Group Limited | Professional & scientific | 1982 |