| Collins Land and Planning Ltd | Professional & scientific | 2025 |
| Collins Property Solutions Ltd | Construction | 2026 |
| Collmart CS Limited | Agriculture & fishing | 2020 |
| Collmart Growers Limited | Wholesale & retail | 1986 |
| Coloursped Services Ltd | Administrative & support | 2018 |
| Come Clean Limited | Wholesale & retail | 1997 |
| Communilab C.I.C. | Information & communication | 2025 |
| Community Cohesion Advocates C.I.C. | Education | 2018 |
| Community Radio Media Limited | Administrative & support | 2016 |
| Company Compliance App Ltd | Information & communication | 2025 |
| Company Publishing Limited | Information & communication | 1993 |
| Compete for Cars Ltd | Arts & recreation | 2026 |
| Complete Bathroom Services(Cambs) Ltd | Construction | 2014 |
| Complete Equipment Group Ltd | Administrative & support | 2008 |
| Complete Healthcare Cambridge Limited | Administrative & support | 2023 |
| Complete Motorsport Solutions Limited | Wholesale & retail | 2014 |
| Composite Refinishing Ltd | Manufacturing | 2024 |
| Computer Network Services Limited | Information & communication | 1989 |
| Computers Aiding Business Limited | | 1985 |
| Comtec Group (International) Limited | Information & communication | 1995 |
| Conbone Entertainment Ltd | Arts & recreation | 2026 |
| Concept Claims Management Ltd | Financial services | 2024 |
| Conecto Limited | Construction | 2017 |
| Connect Education Limited | Professional & scientific | 2018 |
| CONNECT365 Limited | Information & communication | 2017 |
| Connected Parents CIC | Health & social care | 2025 |
| Connections (Brentwood) Management Company Limited | Households | 2007 |
| Connolly-Developments Ltd | Construction | 2014 |
| Conroy Construction Ltd | Construction | 1973 |
| Conscious Living Ltd | Wholesale & retail | 2014 |
| Consilium Strategic Communications Ltd | Professional & scientific | 2013 |
| Construct Marketing Ltd | Professional & scientific | 2019 |
| Constructive Capture Ltd | Information & communication | 2025 |
| Consult RVE Limited | Real estate | 2006 |
| Consultancy International Limited | Professional & scientific | 2025 |
| Contrast Timbers Limited | Manufacturing | 2017 |
| Convert Health Care Ltd | Health & social care | 2021 |
| Cooked by Lizzy Ltd | Hospitality | 2025 |
| Cool Beams Ltd | Manufacturing | 2022 |
| Coolflow AC Ltd | Construction | 2021 |
| Coops Soccer School Limited | Arts & recreation | 2025 |
| Copleys Solicitors LLP | | 2012 |
| Copper INK Ltd | Information & communication | 2022 |
| Coppolaro Sourcing Limited | Wholesale & retail | 2025 |
| Cora Biosciences Limited | Professional & scientific | 2025 |
| Coramy Limited | Real estate | 2023 |
| Coração DE Esperança Ltd | Education | 2025 |
| Core Collective Group Ltd | Professional & scientific | 2026 |
| Coretemp Engineering Ltd | Energy | 2025 |
| Coretemp Plant Hire Ltd | Administrative & support | 2023 |
| Coretemp Refrigeration Ltd | Energy | 2023 |
| Corrall Clarity Ltd | Information & communication | 2026 |
| Cortextra Ltd | Professional & scientific | 2018 |
| COS B & E Ltd | Construction | 2021 |
| Cosa Nostra PR Ltd | Professional & scientific | 2012 |
| Cost Reduction Expense and Account Management Ltd | Professional & scientific | 2010 |
| Counterterrarisk Solutions Ltd | Administrative & support | 2024 |
| Country Road Tyres Ltd | Wholesale & retail | 2024 |
| Country Stoves and Sweeps Ltd | Construction | 2020 |
| Coverspan Limited | Construction | 2009 |
| Coversure Branches Limited | Financial services | 2014 |
| Coversure Insurance Services Limited | Financial services | 1989 |
| Cowhide for Crafts Limited | Wholesale & retail | 2022 |
| CPL Sports Limited | Arts & recreation | 2010 |
| Craig Burkitt Estate Agents Limited | Real estate | 2024 |
| Crazy Cat Furnishings Limited | Other services | 2018 |
| Crazy Manx Ltd | Administrative & support | 2012 |
| Crazy Razor Barber Ltd | Other services | 2025 |
| Crazy Replay Limited | Administrative & support | 2018 |
| CRC Bathrooms Ltd | Construction | 2025 |
| CRC Utilities Ltd | Construction | 2022 |
| Create for a Cause Ltd | Administrative & support | 2025 |
| Creative Behavioural Solutions Ltd | Professional & scientific | 2018 |
| Creative Consultants Ltd | Other services | 2004 |
| Creative Crew Art Workshops Ltd | Education | 2026 |
| Creda Ltd | Wholesale & retail | 2022 |
| Crestmore Limited | Transport & logistics | 2015 |
| Criotom Ltd | Transport & logistics | 2014 |
| Cristo Trans Ltd | Extraterritorial | 2017 |
| Cromwell Quality Care Solutions Ltd | Health & social care | 2021 |
| Cromwell Radio Limited | Extraterritorial | 1996 |
| Cross Continental UK Limited | Wholesale & retail | 2013 |
| Crosshall Properties Limited | Real estate | 1995 |
| Crosslands Vehicle Sales Limited | Wholesale & retail | 2003 |
| Crosslands Vehicles Limited | Wholesale & retail | 2019 |
| Crossways Car Parts Ltd | Wholesale & retail | 2021 |
| Crown Capital Invest Ltd | Real estate | 2025 |
| Crown Mews Management Limited | Real estate | 1987 |
| Crown Star Events Limited | Hospitality | 2024 |
| Crowns Learning Centre CIC | Education | 2020 |
| Croxton Property Management Limited | Households | 2004 |
| Croxton Road (Thetford) Management Company Limited | Households | 1990 |
| Crust Foods Ltd | Hospitality | 2024 |
| Crystal Accountancy Limited | Professional & scientific | 2002 |
| Crysttal Limited | Wholesale & retail | 2022 |
| CS Amenities Limited | Extraterritorial | 2002 |
| CS Property Investment Portfolio Limited | Real estate | 2018 |
| CSH Holdco Ltd | Financial services | 2023 |
| Ctaura Ltd | Health & social care | 2020 |
| Cudh Ltd | Arts & recreation | 2023 |