| Cameron Cuth Developments Ltd | Construction | 2025 |
| Cameron Ward Ltd | Administrative & support | 2015 |
| Cametco Ltd | Health & social care | 2018 |
| Campbells Holding Ltd | Financial services | 2023 |
| Campbells Property Management Ltd | Real estate | 2020 |
| Camrex Corrosion Engineers (Overseas) Limited | | 1936 |
| Camrex Corrosion Engineers Marine (Group) Limited | | 1941 |
| Cams Taxi 2025 Limited | Transport & logistics | 2025 |
| Canyon Electrical Services Ltd | Construction | 2025 |
| Cape Properties NE Ltd | Real estate | 2025 |
| Capital Conservation and Restoration Limited | Construction | 2010 |
| Capital Facility Management Ltd | Construction | 2012 |
| Capture Healthcare Limited | Administrative & support | 2020 |
| Card Guru Limited | Professional & scientific | 2017 |
| Cardicare Ltd | Wholesale & retail | 2020 |
| Care at Home (Wearside) Limited | Health & social care | 2003 |
| Care at South Ltd | Health & social care | 2024 |
| Care Given Ltd | Health & social care | 2025 |
| Care of Choice Limited | Administrative & support | 2022 |
| Careerpedia Limited | Wholesale & retail | 2006 |
| Carevex Limited | Other services | 2019 |
| Cargonest Transport Ltd | Transport & logistics | 2025 |
| Carl Brown Elite Ltd | Administrative & support | 2025 |
| Carley Hill News Ltd | Wholesale & retail | 2026 |
| Carley Lodge (Management) Limited | Households | 2002 |
| Carney Enterprise Ltd | Real estate | 2024 |
| Carone Floors NE Ltd | Wholesale & retail | 2020 |
| Cartec Car Sales Ltd | Wholesale & retail | 2025 |
| Carter Building & Construction Limited | Construction | 2003 |
| Carter Property Holdings Ltd | Real estate | 2024 |
| Carters (2015) Limited | Manufacturing | 2016 |
| Carthew Properties Limited | Real estate | 2020 |
| CAS Mechanical Limited | Manufacturing | 2024 |
| Casa Abruzzo Limited | Hospitality | 2012 |
| Casa North Ltd | Real estate | 2023 |
| Casafrique Global Ltd | Information & communication | 2023 |
| Caspian Building Services Ltd | Construction | 2022 |
| Cassidylocum Ltd | Health & social care | 2021 |
| Cast Maintenance Ltd | Construction | 2010 |
| Castle M Ltd | Real estate | 2019 |
| Castle Mews 2016 Limited | Real estate | 2016 |
| Castle View Enterprise Academy | Education | 2007 |
| Castleview Marketing Ltd | Wholesale & retail | 2024 |
| Casual Line Ltd | Wholesale & retail | 2025 |
| Cauwood Electrical & Inspection Limited | Construction | 2014 |
| Cauwood Transport Ltd | Transport & logistics | 2025 |
| Cavadad Ltd | Construction | 2024 |
| CAZ Properties Ltd | Real estate | 2017 |
| CBS Expert Fire Solutions Limited | Extraterritorial | 2020 |
| CC Electrical Services Contractors Ltd | Construction | 2024 |
| CC Informatics Ltd | Information & communication | 2020 |
| CCB Renewables Ltd | Manufacturing | 2026 |
| Cchoncepts Ltd | Professional & scientific | 2016 |
| Ccsm Plastics Ltd | Wholesale & retail | 2026 |
| CD Access Services Ltd | Professional & scientific | 2019 |
| CDI Construction Group Ltd | Construction | 2019 |
| CDJ Welding Ltd | Manufacturing | 2017 |
| CDL Contracts North East Limited | Construction | 2016 |
| CDM Audio Ltd | Information & communication | 2021 |
| CDM365 Ltd | Professional & scientific | 2026 |
| CDP Plumbing & Heating Ltd | Construction | 2018 |
| CDR Repairs Ltd | Professional & scientific | 2023 |
| Cdsg North East Ltd | Hospitality | 2016 |
| CE Developments (North East) Limited | Real estate | 2015 |
| Ceasars Kitchen Ltd | Hospitality | 2016 |
| Cecateringltd Ltd | Professional & scientific | 2024 |
| Cedar House Sunderland Limited | Health & social care | 2021 |
| Cedar Securities Limited | Real estate | 1955 |
| Cedars Landscaping Limited | Administrative & support | 2007 |
| Cedt Limited | Hospitality | 2019 |
| Ceebyk Couriers Limited | Transport & logistics | 2025 |
| Cef&Caiah Limited | Health & social care | 2023 |
| Celebrity Styling Ltd | Other services | 2022 |
| Cellnua UK Ltd | Health & social care | 2021 |
| Cellnutrition Direct UK Ltd | Wholesale & retail | 2015 |
| Cellnutrition UK Ltd | Hospitality | 2015 |
| Cento Clothing Ltd | Wholesale & retail | 2014 |
| Central Group NE Ltd | Real estate | 2023 |
| Central Jami-Masjid and Islamic Society of Sunderland Limited | Other services | 2025 |
| Central Park (Events) Ltd | Administrative & support | 2020 |
| Central Park Pizza Limited | Hospitality | 2013 |
| Centrebus Holdings Limited | Transport & logistics | 2008 |
| Centurion Fire Safety Solutions Limited | Public administration | 2009 |
| Ceramica Construction Limited | Construction | 2024 |
| Cerezzola Limited | Financial services | 2023 |
| Cergus Prime Care Durham & Sunderland Ltd | Health & social care | 2025 |
| Certax Accounting (Sunderland) Ltd | Professional & scientific | 2015 |
| Ceto Swim Training Group Ltd | Education | 2023 |
| CF Property Group Ltd | Real estate | 2026 |
| CFD Property Group Limited | Real estate | 2025 |
| CGS Technology Limited | Administrative & support | 2022 |
| Chambers and Taylor Ltd | Professional & scientific | 2020 |
| Chambersfield (the ROW) Limited | Households | 1987 |
| Chambersfield Management Company Limited | Households | 1987 |
| Chameleon Connection C.I.C. | Education | 2020 |
| Channels Consulting Ltd | Professional & scientific | 2020 |
| Chantry House Associates Limited | Education | 1988 |
| Chaplin Leisure Limited | Hospitality | 2022 |
| Chapos Tacos Ltd | Hospitality | 2019 |
| Chapter 13 Ltd | Wholesale & retail | 2026 |