| CAD 21 Holdings Limited | Financial services | 2016 |
| CAD 21 Limited | Professional & scientific | 1998 |
| CAD21 Group Ltd | Financial services | 2024 |
| CAL 4KLIFTS Ltd | Wholesale & retail | 2012 |
| CAL Operator Training Limited | Education | 2024 |
| Calderwood Consultancy Limited | Professional & scientific | 2024 |
| Caldow Holdings Ltd | Real estate | 2024 |
| Calmount Limited | Construction | 2014 |
| Campbells Animals Limited | Wholesale & retail | 2025 |
| Capricorn Investments (North East) Ltd | Real estate | 2016 |
| Captains Properties Ltd | Administrative & support | 2020 |
| Cards of the North Ltd | Wholesale & retail | 2021 |
| Caretech Systems Ltd | Construction | 1999 |
| Carols Kidz Care Ltd | Health & social care | 2026 |
| Casa Kitchens & Bedrooms Limited | Manufacturing | 2007 |
| Castle IT NE Ltd | Information & communication | 2026 |
| Catling Bakery Ltd | Manufacturing | 2017 |
| CBAM360 Solutions Ltd | Professional & scientific | 2026 |
| CC Locksmiths Services Ltd | Other services | 2026 |
| Centralock Ltd | Professional & scientific | 2016 |
| Centre for Industrial Growth Ltd | Professional & scientific | 2011 |
| CG Modelling Ltd | Other services | 2020 |
| Cgatm Ltd | Health & social care | 2026 |
| Chalk Road Ltd | Construction | 2020 |
| Charads PUB Company Limited | Administrative & support | 2021 |
| Chargo Tech Ltd | Information & communication | 2019 |
| Charles Carpentry and Construction Ltd | Construction | 2023 |
| Charleston Consultancy Ltd | Real estate | 2021 |
| Charlton Metal Testing Limited | Professional & scientific | 1995 |
| Cherry Box Design Limited | Professional & scientific | 2022 |
| Cheviot Media Limited | Manufacturing | 2011 |
| Chloe Lesley Watts Limited | Extraterritorial | 2022 |
| Chloe Watts Limited | Extraterritorial | 2024 |
| Chloe Wealleans Watts Limited | Extraterritorial | 2022 |
| Chmpcon Ltd | Information & communication | 2026 |
| Chris Moody Roofing Ltd | Construction | 2025 |
| Circo NE Limited | Hospitality | 2022 |
| Circo NE SLG Ltd | Hospitality | 2024 |
| Circuitous Limited | Professional & scientific | 2026 |
| City Slimming Clinic Ltd | Extraterritorial | 2019 |
| CJ Performance Cycles Limited | Wholesale & retail | 2009 |
| Cj's Funhouse Limited | Arts & recreation | 2020 |
| Cjrss Limited | Professional & scientific | 2024 |
| Cjwilson Engineering Ltd | Construction | 2015 |
| Claire Designs Ltd | Wholesale & retail | 2025 |
| Claire Wealleans Limited | Extraterritorial | 2022 |
| Clayton & Sansom Roofing Ltd | Construction | 2026 |
| Clear AS Mudd Productions Limited | Construction | 2021 |
| Clear Cleaning Services Limited | Administrative & support | 2025 |
| Clearline Digital Ltd | Professional & scientific | 2020 |
| Clearpane Glazing Solutions Ltd | Construction | 2026 |
| Clearray Solar Ltd | Wholesale & retail | 2023 |
| Cleo Wealleans-Watts Limited | Extraterritorial | 2022 |
| Clerwood Attics and Construction Ltd | Construction | 2025 |
| Clerwood Building Company Ltd | Construction | 2026 |
| Cm.Renewables Ltd | Other services | 2018 |
| Coast Consulting Engineers Limited | Construction | 2008 |
| Coast Training Ltd | Education | 2024 |
| Colbourne Holdings Limited | Manufacturing | 2023 |
| Cold Brew Events Ltd | Arts & recreation | 2016 |
| Coldstream Commercial Brokers Ltd | Financial services | 2019 |
| Cole Wealleans-Watts Limited | Extraterritorial | 2022 |
| Collaborative Search Ltd | Administrative & support | 2021 |
| Collingwood Property Solutions Limited | Manufacturing | 2025 |
| Cometh Limited | Information & communication | 2022 |
| Cometh Properties Ltd | Real estate | 2023 |
| Compass Auto Body Repair Centre Ltd | Construction | 2026 |
| Compass Care Limited | Health & social care | 2012 |
| Compass Developments (NE) Ltd | Construction | 2009 |
| Compass Motorcompany Ltd | Wholesale & retail | 2024 |
| Complete Accounting North East Ltd | Professional & scientific | 2014 |
| Complete Corporate Finance Limited | Financial services | 2012 |
| Complete Leasing Solutions Limited | Administrative & support | 1998 |
| Computer Problem Solvers Limited | Information & communication | 2009 |
| Connect Contractors NE Ltd | Administrative & support | 2025 |
| CONNECT4EDUCATION Limited | Administrative & support | 2022 |
| Construction Envelope Contracts Ltd | Construction | 2019 |
| Contamination Control Laboratories Ltd | Professional & scientific | 2021 |
| Continental Disc UK Limited | Administrative & support | 1992 |
| Control & Move Fitness CIC | Other services | 2021 |
| Copperchase Limited | Transport & logistics | 1990 |
| Corelink Group Ltd | Administrative & support | 2026 |
| Coretorque Offshore Ltd | Manufacturing | 2026 |
| Cornerstone Evolution Ltd | Construction | 2026 |
| Cortland U.K. Holdings Limited | Manufacturing | 2000 |
| Cosella Ltd | Information & communication | 2024 |
| Cosy@Home Limited | Wholesale & retail | 2019 |
| Craig Enterprises Limited | Water & waste | 2001 |
| Craig Healthcare Holdings Limited | Financial services | 2022 |
| Craig Healthcare LLP | | 2009 |
| Craig Healthcare Property Limited | Real estate | 2022 |
| Cramlington & District Health Alliance Limited | Health & social care | 2024 |
| Cramlington Barbers Ltd | Hospitality | 2026 |
| Cramlington Car Parts Limited | Wholesale & retail | 2014 |
| Cramlington Cleaning Solutions Ltd | Administrative & support | 2025 |
| Cramlington Development Trust Limited | Public administration | 2011 |
| Cramlington Eyecare Limited | Wholesale & retail | 2015 |
| Cramlington Family Funerals Ltd | Other services | 2021 |
| Cramlington Health Ltd | Wholesale & retail | 2023 |
| Cramlington House Limited | Health & social care | 2009 |