| CJR Engineering Ltd | Professional & scientific | 2018 |
| CJR Wind Ltd | Construction | 2025 |
| CJS Scaffolding Limited | Construction | 2008 |
| CKE 2011 Ltd | Wholesale & retail | 2023 |
| Ckhv Limited | Professional & scientific | 2025 |
| Ckspenceley Ltd | Construction | 2026 |
| CL Arnett Logistics Ltd | Transport & logistics | 2025 |
| CL Burns Logistics Ltd | Transport & logistics | 2025 |
| CL Operatives Ltd | Construction | 2020 |
| Cladfix (NE) Ltd | Construction | 2026 |
| Claire Abbey Quantum Healing Limited | Health & social care | 2024 |
| Claire Birch Recruitment Limited | Administrative & support | 2006 |
| Clam Developments Limited | Professional & scientific | 2017 |
| Clando PR Limited | Wholesale & retail | 2023 |
| Clarence 18 Limited | Administrative & support | 2018 |
| Clarity Electrical Solutions Limited | Professional & scientific | 2013 |
| Clarity FS Ltd | Professional & scientific | 2011 |
| Clark Auto Repairs Service Garage Limited | Wholesale & retail | 2011 |
| CLC Handyman Ltd | Construction | 2025 |
| Cleanwise Retail Group Limited | Wholesale & retail | 2020 |
| Cleveland Car Systems Limited | Construction | 2016 |
| Cleveland Data Shred Ltd | Administrative & support | 2018 |
| Cleveland Inspection Services Ltd. | Professional & scientific | 2019 |
| Cleveland Process Designs Limited | Professional & scientific | 1996 |
| Cleveland Reclamation Limited | Administrative & support | 1998 |
| Cleveland Valley Limited | Wholesale & retail | 2020 |
| Cleveland Waste Paper Limited | Water & waste | 2003 |
| CLI Cable Ltd | Construction | 2018 |
| Clmc Properties Ltd | Real estate | 2024 |
| Cloontia Construction Ltd | Real estate | 2026 |
| Cloud 9 Property Management Ltd | Households | 2026 |
| Cloud House Homes Limited | Real estate | 2017 |
| Cloudhouse Group Limited | Financial services | 2026 |
| Clova Construction Services Limited | Administrative & support | 2024 |
| Clover Drive 1970 Limited | Extraterritorial | 2014 |
| Club 95 Limited | Wholesale & retail | 2025 |
| CLW Enterprises Limited | Hospitality | 2017 |
| Cmacca Ltd | Professional & scientific | 2025 |
| CMC Consultancy Services Ltd | Professional & scientific | 2024 |
| CMC Inspection Services Ltd | Professional & scientific | 2014 |
| Cmdennison Joinery Limited | Construction | 2024 |
| CMG (North East) Ltd | Hospitality | 2020 |
| CMI Inspection Services Limited | Professional & scientific | 2015 |
| Cmifsw Ltd | Health & social care | 2025 |
| CNJ Lifting Services Limited | Administrative & support | 2016 |
| Coast Kitchens & Bedrooms Limited | Manufacturing | 2007 |
| Coast Road Educate Limited | Education | 2026 |
| Coastal Canine Ltd | Other services | 2025 |
| Code Whisperer Limited | Information & communication | 2005 |
| Coded Canvas Ltd | Professional & scientific | 2025 |
| Cola COE Limited | Extraterritorial | 2007 |
| Colbat Ltd | Construction | 2019 |
| Cole Construction NE Limited | Construction | 2018 |
| Cole Hill Farm Limited | Agriculture & fishing | 2016 |
| Colesome Developments Ltd. | Construction | 2025 |
| Colesome Lettings Ltd | Real estate | 2026 |
| Colettingham Properties Ltd | Real estate | 2021 |
| Collectors and Motorsport Limited | Wholesale & retail | 2020 |
| Collier Estates Ltd | Real estate | 2017 |
| Collinson Properties Limited | Real estate | 2018 |
| Com-Truck Limited | Wholesale & retail | 1990 |
| Combined Utilities (Hartlepool) Ltd | Other services | 2019 |
| Combined Utilities Group Limited | Other services | 2022 |
| Coml Marine Ltd | Education | 2022 |
| Command Solutions Limited | Professional & scientific | 2016 |
| Commelec Ltd | Construction | 2017 |
| Commercial Cleaning Site Crews Ltd | Administrative & support | 2023 |
| Commercial Plastering North East Limited | Construction | 2014 |
| Commondale Project Solutions Limited | Construction | 2026 |
| Community Waves CIC | Information & communication | 2022 |
| Complete Commercial and Domestic Services Ltd | Construction | 2025 |
| Composed Training Limited | Information & communication | 2026 |
| Composite Doors 2 U Ltd | Manufacturing | 2015 |
| Concat Holdings Limited | Professional & scientific | 1994 |
| Conductive Life CIC | Health & social care | 2019 |
| Coniscliffe Consultancy Services Limited | Professional & scientific | 2020 |
| Coniscliffe Investments Limited | Real estate | 2023 |
| Connect Services Group Limited | Administrative & support | 2022 |
| Connect Training Services Limited | Administrative & support | 2019 |
| Connected GAS, Heating & Water Limited | Construction | 2006 |
| Connor's IT Solutions Ltd | Information & communication | 2013 |
| Conquest OIL NRG Ltd | Extraterritorial | 2018 |
| Conroy Close Management Company Ltd | Real estate | 2025 |
| Construction Resolution Services Ltd | Construction | 2025 |
| Consult Assist Ltd | Professional & scientific | 2018 |
| Consulting Compliance Services Ltd | Professional & scientific | 2019 |
| Contessa Curtains Limited | Manufacturing | 1977 |
| Continued Health Clinic Limited | Health & social care | 2006 |
| Contract Laboratory Services Limited | Professional & scientific | 2006 |
| Contract Supplies (North East) Ltd | Wholesale & retail | 2024 |
| Cook Fibre UK Ltd | Construction | 2023 |
| Cooke Property Services Limited | Real estate | 2019 |
| Cooking Creations Ltd | Hospitality | 2020 |
| Coolmore Productions Limited | Information & communication | 2009 |
| Coopers of Elwick Limited | Hospitality | 2019 |
| Cor's Camper Conversions Ltd | Wholesale & retail | 2025 |
| Corbett Interiors Ltd | Manufacturing | 2021 |
| Corbycroft Interiors Ltd | Wholesale & retail | 2020 |
| Corinthia Limited | Construction | 2014 |
| Corola Ltd | Transport & logistics | 2017 |