| Commercial Property Management Group Ltd | Professional & scientific | 2024 |
| Commercialfinancecompany(Essex) Ltd | Financial services | 2019 |
| Comms Planner Ltd | Information & communication | 2024 |
| Complete Commercial Services Limited | Construction | 2016 |
| Complete Freight and Customs Limited | Transport & logistics | 2023 |
| Complete Glass Ltd | Construction | 2022 |
| Compute Services Ltd | Information & communication | 2023 |
| Con-Fused Group Limited | Construction | 2017 |
| Con-Fused Installations Limited | Construction | 2017 |
| Con-Fused Maintenance Limited | Construction | 2017 |
| Conesive Consulting Limited | Professional & scientific | 2024 |
| Conheeney Group Ltd | Agriculture & fishing | 2023 |
| Connect Interiors Ltd | Construction | 2024 |
| Connected Safety NET Limited | Administrative & support | 2019 |
| Constant Supplies Limited | | 1989 |
| Construction Site Recruitment Ltd | Construction | 1999 |
| Contact Ceilings Limited | Construction | 1990 |
| Container Connect Limited | Wholesale & retail | 2019 |
| Contemporata Limited | Manufacturing | 2014 |
| Cool 69 Limited | Manufacturing | 2011 |
| Cool-A-Room Ltd | Construction | 2025 |
| Cooper Investment Properties Ltd | Real estate | 2022 |
| Cooptech Limited | Professional & scientific | 2012 |
| COP Variety Box Limited | Wholesale & retail | 2002 |
| Coprogrammer Ltd | Professional & scientific | 2025 |
| Cordelia's Cattery Ltd | Agriculture & fishing | 2026 |
| Core Four Investments Group Limited | Real estate | 2025 |
| Core Studio Essex Limited | Arts & recreation | 2026 |
| Cornucopia Aplenty Ltd | Wholesale & retail | 2021 |
| Cornwall Bailiff Services Limited | Professional & scientific | 2024 |
| Cornwall Collections and Recovery Ltd | Administrative & support | 2025 |
| Corporate Workplace & Energy Management Limited | Administrative & support | 2016 |
| COS Catering Ltd | Hospitality | 2019 |
| Cost Compare Limited | Information & communication | 2015 |
| Costin Mckenzie Limited | Other services | 2003 |
| Cosu FC Limited | Arts & recreation | 2023 |
| Cotswold Fairford Waterside Limited | Financial services | 2025 |
| Cotswolds Lakes Limited | Hospitality | 2024 |
| Cottage Commercial Property Limited | Real estate | 2020 |
| Cottage Property Development Limited | Construction | 2018 |
| Cottage Property Limited | Real estate | 2016 |
| Countrywide Fencing Limited | Construction | 2014 |
| Countrywide Industrial Flooring Ltd | Construction | 2025 |
| Countrywide Security Fencing Ltd | Construction | 2026 |
| Covessee Ltd | Wholesale & retail | 2025 |
| COW Shed Properties Ltd | Construction | 2024 |
| Cowrie Communications Limited | Professional & scientific | 2017 |
| CP (CP) Limited | Professional & scientific | 2010 |
| CP Heating & Plumbing Services Ltd | Other services | 2017 |
| CP Property Maintenance Ltd | Construction | 2010 |
| Cpsk Analytics & Solutions LLP | | 2023 |
| Craig's Curtains and Blinds Limited | Construction | 2025 |
| Cranbourne Builders Limited | Construction | 2009 |
| Crane Consultants & Advocacy Limited | Professional & scientific | 2022 |
| Craybeck Law LLP | | 2018 |
| Crayside Limited | Agriculture & fishing | 2023 |
| Crazy Golf Ltd | Arts & recreation | 2019 |
| Creapsoft Limited | Information & communication | 2009 |
| Creation Internet Services Limited | Information & communication | 2001 |
| Creme Professional Services Ltd | Professional & scientific | 2024 |
| Crestinvestors Limited | Real estate | 2023 |
| Crimmen Wealth Management Limited | Professional & scientific | 2014 |
| Crimsoncube Limited | Information & communication | 2007 |
| Criss Supplies Ltd. | Administrative & support | 2010 |
| Cristina Salvi Ltd | Professional & scientific | 2022 |
| Croft Family Investments Ltd | Real estate | 2025 |
| Cronin Limited | Health & social care | 2013 |
| Cronos Services Limited | Information & communication | 2018 |
| Crosby Land Ltd | Financial services | 2002 |
| Cross & Tillett Lettings & Property Management Ltd | Real estate | 2024 |
| Cross County Holdings Ltd | Real estate | 2018 |
| Crowes Quality Homes Ltd | Real estate | 2021 |
| Crownhill Care Services PVT Ltd | Administrative & support | 2023 |
| Crownmed Services Limited | Professional & scientific | 2004 |
| CRR Group Ltd | Professional & scientific | 2025 |
| CRS Interiors Limited | Construction | 2017 |
| Crunchspark Limited | Professional & scientific | 2023 |
| Crystal 363 Ltd | Real estate | 2020 |
| CS Thermal Limited | Construction | 2024 |
| CSB Construction and Development Limited | Construction | 2026 |
| CSF Construction Ltd | Construction | 2024 |
| CSI Technical Ltd | Administrative & support | 2016 |
| CSM Security Solutions Ltd | Administrative & support | 2022 |
| Css/Raw Holdings Limited | Construction | 2017 |
| CSW Carpentry and Construction Ltd | Construction | 2025 |
| CTC Media Ltd | Professional & scientific | 2024 |
| CTE Electrical Services Ltd | Construction | 2023 |
| CTO Software Limited | Administrative & support | 2023 |
| CTS Technical Solutions Limited | Information & communication | 2015 |
| Cukur Limited | Hospitality | 2021 |
| Cullen & SON Site Services Limited | Construction | 2017 |
| Cullen Scaffolding Limited | Construction | 2021 |
| Cultivate and Nurture Ltd | Professional & scientific | 2024 |
| Culverhouse Construction Limited | Construction | 2024 |
| Cumberland Packaging Limited | Manufacturing | 1985 |
| Cumulus Trading Limited | Real estate | 2012 |
| Cunningplan Limited | Professional & scientific | 2022 |
| Curbside Gamers Limited | Other services | 2021 |
| Curiouser London Limited | Professional & scientific | 2025 |
| Curly G Limited | Other services | 2016 |