| Coffee Master Vibe Ltd | Hospitality | 2022 |
| Cofunction Ltd | Professional & scientific | 2017 |
| Cognisoft Holdings Limited | Professional & scientific | 2020 |
| Cognisoft Limited | Information & communication | 1984 |
| Cognizant Services Ltd | Information & communication | 2022 |
| Colab Spaces Group Limited | Real estate | 2019 |
| Colbert Group Ltd | Financial services | 2023 |
| Colbert Stud Ltd | Agriculture & fishing | 2022 |
| Cold Air (Essex) Limited | Construction | 2017 |
| Come Shine With ME Cleaning Limited | Administrative & support | 2018 |
| Come Shine With ME Essex Limited | Administrative & support | 2018 |
| Commercial Platforms International Limited | Information & communication | 2005 |
| Complete Building & Maintenance Ltd | Construction | 2021 |
| Complete Picture UK Limited | Information & communication | 1995 |
| Completely Clean Ltd | Administrative & support | 2022 |
| Completely Cleansed Ltd | Extraterritorial | 2021 |
| Coniston Consulting Limited Ltd | Financial services | 2010 |
| Conscience UK Limited | Professional & scientific | 2004 |
| Construction Projects and Programme Services Limited | Construction | 2023 |
| Construction Sealants (North-West) Limited | Extraterritorial | 2008 |
| Construction Sealants (Southern) Limited | Extraterritorial | 2008 |
| Construction Sealants Limited | Construction | 1990 |
| Contract Repair Services Limited | Real estate | 2016 |
| Convent Close Management Limited | Real estate | 2017 |
| Cool Interiors Limited | Construction | 2024 |
| Coolus Air Conditioning Ltd | Construction | 2025 |
| Coop Contractors Ltd | Construction | 2022 |
| Cooperative Contractors Ltd | Construction | 2013 |
| Corbets TEY Practice Ltd | Health & social care | 2022 |
| Corby Property Holdings Limited | Transport & logistics | 2014 |
| Core Services Coordination Limited | Administrative & support | 2023 |
| Corkyconsultancy Ltd | Administrative & support | 2013 |
| Cortina Property Ltd | Construction | 2023 |
| Cosy Corner Coffee Ltd | Hospitality | 2025 |
| Cotach Ltd | Real estate | 2025 |
| Cotoc Ltd | Professional & scientific | 2022 |
| Courtlands Property / Maintenance Limited | Real estate | 1999 |
| Cowling Consultancy Limited | Professional & scientific | 2014 |
| CPI Media Holdings Limited | Information & communication | 2010 |
| CPW Electrical Solutions Limited | Construction | 2013 |
| Crafting Civic Change Ltd | Professional & scientific | 2023 |
| Craigen Driving School Ltd | Education | 2023 |
| Cranham Bangla Restaurant Ltd | Hospitality | 2019 |
| Cranham Car Wash Limited | Wholesale & retail | 2024 |
| Cranham Golf Course Limited | Arts & recreation | 2019 |
| Cranham Hall Mews Management Company Limited | Households | 2009 |
| Cranham Holdings Ltd | Arts & recreation | 2020 |
| Cranham Leisure LLP | | 2009 |
| Cranham Solutions Limited | Construction | 2025 |
| Cranston Management Solutions Limited | Professional & scientific | 2015 |
| Creations Group Ltd | Financial services | 2026 |
| Creative Chaos Illustration Limited | Extraterritorial | 2012 |
| Credipay CIS Limited | Administrative & support | 2017 |
| Credipay Contractor Limited | Administrative & support | 2017 |
| Credipay Limited | Administrative & support | 2017 |
| Credipay Umbrella Limited | Administrative & support | 2017 |
| Crew Assist Ltd | Transport & logistics | 2024 |
| CRF Insulations Ltd | Manufacturing | 2025 |
| Cridders Swim School C.I.C. | Education | 2019 |
| Cristal Staff Clean Limited | Administrative & support | 2026 |
| Cromwell Manor Functions Limited | Hospitality | 1988 |
| Cross Leisure Group Ltd | Health & social care | 2025 |
| Cross-Cars Ltd | Wholesale & retail | 2026 |
| Crostata Limited | Hospitality | 2022 |
| Crown Historical Investments Ltd | Wholesale & retail | 2022 |
| Crownchoice Limited | Construction | 1978 |
| Crystal Chandelier Services Limited | Other services | 2020 |
| Cscm (UK) Limited | Information & communication | 2014 |
| Csfroofing Ltd | Construction | 2025 |
| CSK Homes Limited | Real estate | 2024 |
| CSL Hire & Sales Ltd | Administrative & support | 2015 |
| CSS Trustees Limited | Construction | 2025 |
| CTC Express Limited | Transport & logistics | 2010 |
| Culture Lounge Limited | Hospitality | 2019 |
| Curlew Consultancy LLP | | 2025 |
| Curtlee & Co Ltd | Manufacturing | 2024 |
| Custom Air Solutions Ltd | Construction | 2021 |
| Custom Sight and Sound Ltd | Construction | 2002 |
| Customs Insights Consultancy Limited | Transport & logistics | 2000 |
| CWC Logistics Ltd | Transport & logistics | 2009 |
| CWR Services Limited | Administrative & support | 2022 |
| Cybotron Consulting Limited | Information & communication | 1992 |
| D Quinn Roofing Limited | Construction | 2015 |
| D Smith Brickwork & Construction Ltd | Construction | 2015 |
| D&J Build Ltd | Construction | 2022 |
| D. K. Charles Landscapes and Construction Limited | Construction | 2013 |
| D.L.S Plasterworks Limited | Construction | 2019 |
| Dagenham Landscapes Limited | Administrative & support | 1973 |
| Daisy Blinds Limited | Wholesale & retail | 2024 |
| Dallison Enterprise Limited | Professional & scientific | 2024 |
| Dallison Holdings Limited | Wholesale & retail | 2026 |
| Dallison Property Limited | Real estate | 2026 |
| Dals Transport Ltd | Transport & logistics | 2026 |
| Dancematic Ltd | Extraterritorial | 2016 |
| Dandy Productions Limited Liability Partnership | | 2002 |
| Danglers Nation Limited | Wholesale & retail | 2014 |
| Daphnex Ltd | Professional & scientific | 2022 |
| Data Administration Ltd | Information & communication | 2012 |
| Data Distribution Limited | Information & communication | 2013 |
| Data Partners Ltd | Information & communication | 2024 |