| Carbar Automotive Ltd | Wholesale & retail | 2019 |
| Caribe Coffee Company Ltd | Manufacturing | 2018 |
| Carnell Ltd | Construction | 2024 |
| Carr's Corner Limited | Wholesale & retail | 2019 |
| Carrongrange Enterprises Ltd | Administrative & support | 2015 |
| Carterside Management Company Limited | Households | 2015 |
| Cask (OMS) Limited | Construction | 2025 |
| Cast Academy Ltd | Arts & recreation | 2019 |
| Cast. Agency Ltd | Professional & scientific | 2020 |
| Castle Chiropractic Limited | Health & social care | 2014 |
| Castle Green Developments (North East) Limited | Real estate | 2020 |
| Castle Green Holdings Ltd | Real estate | 2017 |
| Castle Morpeth Taxis Ltd | Transport & logistics | 2019 |
| Castle North Plumbing & Heating Ltd | Construction | 2017 |
| Castle Square Morpeth Limited | Hospitality | 2018 |
| Castrovala Ltd | Information & communication | 1998 |
| Catchburn Vineyard Limited | Agriculture & fishing | 2023 |
| Cavil Head Management Company Limited | Households | 2016 |
| CB Recovery and Transportation Ltd | Transport & logistics | 2025 |
| Cbtne Ltd | Professional & scientific | 2026 |
| CC Harbour Limited | Hospitality | 2023 |
| CCI Thompson Ltd | Professional & scientific | 2018 |
| CCM Investments NE Limited | Real estate | 2025 |
| CDP (NE) Limited | Extraterritorial | 2024 |
| CDS Electrical Solutions Ltd | Construction | 2011 |
| Cedar Publishing Limited | Information & communication | 2025 |
| Certa-Cito Welding Inspection Ltd | Professional & scientific | 2018 |
| CH Mechanical Ltd | Professional & scientific | 2024 |
| Chambers Health Limited | Education | 2023 |
| Chantryplay Limited | Hospitality | 2023 |
| Char Mausum Limited | Hospitality | 2007 |
| Charles Lyndon Holdings Ltd | Financial services | 2019 |
| Charles Lyndon Homes (Bradford) Ltd | Construction | 1998 |
| Charles Lyndon Homes Ltd | Construction | 1987 |
| Charlotte Peacock Associates Limited | Professional & scientific | 2011 |
| Charlton Motors N.E. Ltd | Wholesale & retail | 2025 |
| Chbd Consultancy Ltd | Information & communication | 2021 |
| Chef Before Gaming Ltd | Wholesale & retail | 2019 |
| Cheviot Estates Limited | Real estate | 2026 |
| Cheviot Meadows Management Company Limited | Real estate | 2021 |
| Cheviot Plant Hire Limited | Construction | 2020 |
| Cheviot View Leisure Ltd | Construction | 2021 |
| Childcare @ Dawn to Dusk Ltd | Health & social care | 2018 |
| Christopher Carey Ltd | Professional & scientific | 2015 |
| Chrysalis Marketing Ltd | Administrative & support | 2022 |
| Churchburn Digital Technology Limited | Information & communication | 2025 |
| Circolo Sports Ltd | Manufacturing | 2024 |
| Cityreal Ltd | Administrative & support | 2010 |
| CJM (North East) Limited | Construction | 2023 |
| Claire Corley Limited | Professional & scientific | 2015 |
| Clark Homes Group Limited | Financial services | 2015 |
| Clark Homes Limited | Construction | 1998 |
| Claybank Holdings Limited | Real estate | 2019 |
| Claymore Miniatures Ltd | Arts & recreation | 2020 |
| Clean Plus North East Cleaning Solutions Ltd | Administrative & support | 2026 |
| Clearpath Digital Services Ltd | Information & communication | 2026 |
| Click Property Portal Ltd | Information & communication | 2022 |
| Cliffewood Rise Management Company Limited | Households | 2017 |
| Clifton Engineering (North East) Limited | Manufacturing | 1993 |
| Clifton Holdings (North East) Limited | Financial services | 2014 |
| Clifton Investco (North East) Ltd | Professional & scientific | 2017 |
| Clifton Lane Farm Ltd | Agriculture & fishing | 2019 |
| Clifton Shires Management Company Limited | Administrative & support | 1997 |
| Clifton Technologies Limited | Manufacturing | 2019 |
| Cloudy Apps Ltd | Information & communication | 2017 |
| Clubwise UK Limited | Real estate | 2003 |
| CN Access Ltd | Other services | 2024 |
| Coast Technology Limited | Information & communication | 2013 |
| Coastal and Countryside Cleaning Ltd | Administrative & support | 2026 |
| Coastal Cottages Amble Ltd | Hospitality | 2026 |
| Coastal Cottages Northumberland Ltd | Hospitality | 2020 |
| Coastline Cleans Limited | Administrative & support | 2025 |
| Coble Quay Block 4 Limited | Households | 2017 |
| Coble Ventures Limited | Extraterritorial | 2013 |
| Codec Network Limited | Information & communication | 2026 |
| Codeworthy Limited | Information & communication | 2018 |
| Cohyphen Innovation Ltd | Information & communication | 2018 |
| Colab Realty Ltd | Households | 2025 |
| Colin Campbell Technical Services Limited | Professional & scientific | 2022 |
| Colin Thompson Photography Limited | Professional & scientific | 2003 |
| Coliseum Bouldering Ltd | Arts & recreation | 2024 |
| Colour Morph Labs Limited | Professional & scientific | 2025 |
| Comma Print Limited | Extraterritorial | 2007 |
| Command Print Ltd | Manufacturing | 2015 |
| Communities CAN (North East) C.I.C. | Administrative & support | 2018 |
| Community Action Northumberland | Other services | 2011 |
| Confignum Ltd | Professional & scientific | 2024 |
| Connell Fishing Limited | Administrative & support | 2004 |
| Consumer Refund Service Ltd | Professional & scientific | 2011 |
| Contact (Morpeth Mental Health Group) Ltd | Health & social care | 2007 |
| Continuum Equity Group Ltd | Financial services | 2025 |
| Contractsadvice Limited | Professional & scientific | 2025 |
| Convey With ME Ltd | Professional & scientific | 2010 |
| Conveyancing Made Easy Limited | Professional & scientific | 2020 |
| Conway House (Rothbury) Management Limited | Households | 2003 |
| Cookswell Garage Limited | Real estate | 1980 |
| Copper House Properties Ltd | Real estate | 2020 |
| Coquet Animal Health Limited | Professional & scientific | 2018 |
| Coquet Clean Ltd | Administrative & support | 2025 |
| Coquet Confectioners Ltd | Wholesale & retail | 2024 |