| C Spurr Ltd | Wholesale & retail | 2023 |
| C-T-A Ltd | Other services | 2026 |
| Caitlyn Julie Limited | Wholesale & retail | 2025 |
| Cali G Ltd | Manufacturing | 2020 |
| Camden Management Property Lettings Ltd | Real estate | 2011 |
| Capital Lofts & Construction Ltd | Construction | 2021 |
| Capital Lofts Limited | Construction | 2013 |
| Care & Reablement Solutions Limited | Health & social care | 2024 |
| Casa Conveyancing Limited | Professional & scientific | 2025 |
| Casa Group Holdings Limited | Financial services | 2016 |
| Castle Architectural Metalwork Ltd | Manufacturing | 2011 |
| Castle Fabrication & Installation Limited | Manufacturing | 1994 |
| Castledene Lettings Limited | Real estate | 2008 |
| CDW (Northern) Limited | Real estate | 2011 |
| CDY Electrical Contractors Ltd | Construction | 2026 |
| CDY Property Group Ltd | Real estate | 2024 |
| Ceefox Developments Limited | Construction | 2021 |
| Ceefox Holdings Limited | Financial services | 2015 |
| Ceefox Properties Limited | Real estate | 2015 |
| Ceefox Sports Consultancy Limited | Arts & recreation | 2011 |
| Centrally Managed Ltd | Other services | 2024 |
| CG Luxury Travel Ltd | Administrative & support | 2025 |
| Chambers & Slater Limited | Professional & scientific | 2016 |
| Chase Construction & Commercial Management Ltd | Construction | 2026 |
| Chelton Products Ltd | Wholesale & retail | 2024 |
| Chemical Process Solutions Limited | Manufacturing | 2001 |
| Chen 2019 Ltd | Hospitality | 2019 |
| Churchills Managment Limited | Hospitality | 2022 |
| Ciiicle Ltd | Information & communication | 2011 |
| City GAS Plumbing and Heating Limited | Construction | 2019 |
| City Lets (North East) Limited | Real estate | 2003 |
| Cj-Recruitment Global Ltd | Administrative & support | 2023 |
| CK Autos Ltd | Wholesale & retail | 2025 |
| Claire Holdings Ltd | Hospitality | 2023 |
| Clearwater Developments Ltd | Real estate | 2011 |
| Clearwater Utilities Ltd | Households | 2018 |
| Cliff House Service Station Ltd | Wholesale & retail | 2009 |
| CMS (North East) Ltd | Construction | 2020 |
| CMS Fleet (UK) Limited | Extraterritorial | 2018 |
| Coast 2 Coast Builders Ltd | Construction | 2026 |
| Coast to Country Properties Ltd | Real estate | 2018 |
| Coastal Facilities Management Ltd | Construction | 2024 |
| Coastal Group NE Ltd | Financial services | 2024 |
| Coastal Joinery & Building Services Ltd | Construction | 2019 |
| Cogent Assets Ltd | Real estate | 2023 |
| Colourwayuk Limited | Extraterritorial | 2019 |
| Compound Joinery Ltd | Construction | 2020 |
| Connoisseur IT Ltd | Information & communication | 2015 |
| Construction Jobs Australia Ltd | Professional & scientific | 2024 |
| Construction Solutions (NE) Limited | Professional & scientific | 2013 |
| Cooper Potter & Partners Limited | Professional & scientific | 2026 |
| Corehaus Ltd | Construction | 2014 |
| Cork & Coffee Ltd | Hospitality | 2023 |
| Corporate Search Limited | Professional & scientific | 2002 |
| Costcutters (Murton) Limited | Wholesale & retail | 2007 |
| Country and Equine Limited | Extraterritorial | 2021 |
| Country and Equine Properties Limited | Real estate | 2025 |
| Crake Group Ltd | Construction | 2023 |
| Creativepop CIC | Arts & recreation | 2019 |
| Croan Transport Limited | Transport & logistics | 2020 |
| CS Technical Support Limited | Information & communication | 2014 |
| CT Commercial Letting Ltd | Real estate | 2025 |
| Cucuk Ltd | Wholesale & retail | 2025 |
| Curate Labs Limited | Information & communication | 2026 |
| CUT My Overheads Limited | Administrative & support | 2011 |
| CW Taxis Limited | Transport & logistics | 2026 |
| CWA Plotworks Ltd | Construction | 2016 |
| D & D Autocare Limited | Wholesale & retail | 2016 |
| D & D Healthcare (NE) Ltd | Wholesale & retail | 2021 |
| D Anderson Engineering Solutions Limited | Professional & scientific | 2015 |
| D Foster (Services) Ltd | Transport & logistics | 2022 |
| D R G M Limited | Hospitality | 2012 |
| D. Roberts Organ Builders Limited | Manufacturing | 2003 |
| D.H.Car Sales (NE) Ltd | Wholesale & retail | 2019 |
| D3 (Murton) Limited | Health & social care | 2015 |
| Darlington Dog Show Society Limited | Arts & recreation | 2012 |
| Darren Dugdale Financial Services Limited | Professional & scientific | 2025 |
| David Wild TM Limited | Construction | 2019 |
| Deadline Pest Control (NE) Limited | Administrative & support | 2025 |
| Dhhunter Group Ltd | Wholesale & retail | 2024 |
| Diamond IT Ltd | Information & communication | 2015 |
| Dixon Efficiency Sales Ltd | Professional & scientific | 2025 |
| Dizzy Pixels Ltd | Information & communication | 2013 |
| DM Electrical Contractor's Ltd | Construction | 2020 |
| Douglas Corkhill Limited | Manufacturing | 2011 |
| Downeys of Rainton Ltd | Hospitality | 2017 |
| Downeys of Ropery Walk Ltd | Hospitality | 2016 |
| Downeys of Seaham Ltd | Hospitality | 2011 |
| Downeys Plaza Ltd | Hospitality | 2020 |
| Downeys Seaburn Ltd | Hospitality | 2020 |
| Downeys Seafood Ltd | Hospitality | 2023 |
| DR Karasek Limited | Health & social care | 2015 |
| DR Security Solutions Limited | Administrative & support | 2022 |
| DRF Comms Ltd | Information & communication | 2016 |
| Drilcorp Limited | Construction | 1992 |
| Dsbr Ltd | Construction | 2025 |
| DST Shutters Limited | Construction | 2013 |
| DTA Drinks Ltd | Wholesale & retail | 2019 |
| DTM Consutancy Limited | Professional & scientific | 2025 |
| DTM Trading Limited | Wholesale & retail | 2025 |