| Clear Flow Environmental Technologies Limited | Administrative & support | 2004 |
| Clearstream Limited | Professional & scientific | 1989 |
| Clearview Contracting Ltd | Professional & scientific | 2017 |
| Clentec Limited | Extraterritorial | 2020 |
| Clerimis Limited | Other services | 2017 |
| Cleveland Data Services Limited | Information & communication | 1977 |
| Cleveland Independent Theatre Company Limited | Arts & recreation | 1979 |
| Cleveland Motorhomes Limited | Wholesale & retail | 1971 |
| Cleveland Sports and Social Club Limited | Hospitality | 2021 |
| Cleveland Systems Engineering Limited | Information & communication | 1997 |
| Cleveland Tontine Holdings Limited | Professional & scientific | 1989 |
| Cleveland Tontine Limited | Hospitality | 1976 |
| Cleverclogs (Yarm) Limited | Education | 2015 |
| CLG Psychology Ltd | Education | 2024 |
| CLH32 Solutions Ltd | Information & communication | 2018 |
| Clifton Properties North East Limited | Real estate | 2013 |
| Clifton Roofing Ltd | Construction | 2021 |
| Clinic 36 Ltd | Wholesale & retail | 2009 |
| Clinical Consulting VE Limited | Public administration | 2020 |
| Clinitrain Ltd | Health & social care | 2021 |
| Clinivi Ltd | Health & social care | 2024 |
| Clinivi Wellness CIC | Arts & recreation | 2026 |
| Clinton Building Services Ltd | Construction | 2020 |
| Clive Owen Corporate Finance Limited | Professional & scientific | 2022 |
| CLM Properties (NE) Limited | Real estate | 2017 |
| Clng Properties Limited | Real estate | 2022 |
| Close Thornton LLP | | 2009 |
| Closecooper Energy Ltd | Energy | 2025 |
| Closecooper Holdings Ltd | Financial services | 2024 |
| Closecooper Ltd | Construction | 2020 |
| Closecooper Renewables Ltd | Construction | 2025 |
| Closecooper Utilities Consultancy Ltd | Energy | 2025 |
| Closedwn Ltd | Wholesale & retail | 2025 |
| Cloud 11 Property Ltd | Construction | 2026 |
| Clough Electrical Contractors Ltd | Construction | 2021 |
| Clough Estates Ltd | Construction | 2026 |
| Clough Group Holdings Ltd | Financial services | 2026 |
| CLR Software Ltd | Information & communication | 2015 |
| Club Sport Support Limited | Administrative & support | 2017 |
| Clutch Express Limited | Wholesale & retail | 1994 |
| CM Door Services Ltd | Construction | 2025 |
| CM Site Services Ltd | Construction | 2023 |
| CMB Telecommunications Limited | Information & communication | 2021 |
| CMH Decorators Limited | Construction | 2025 |
| CNA Rigging and Lifting Solutions Ltd | Construction | 2026 |
| Cnch Limited | Other services | 2018 |
| Cnfm Renewables Ltd | Professional & scientific | 2020 |
| Co-B-Tech UK Limited | Manufacturing | 1991 |
| Coached by Greeny Limited | Wholesale & retail | 2025 |
| Coachmatic Ltd | Information & communication | 2023 |
| Coanda Aeronautical Turbines Ltd | Professional & scientific | 2018 |
| Cobon Validation Ltd | Construction | 2025 |
| Coby Creighton Logistics Ltd | Transport & logistics | 2025 |
| Cockerill Global Limited | Professional & scientific | 2017 |
| Cockerill Property Investments Limited | Real estate | 2021 |
| Cockerton Fisheries Ltd | Hospitality | 2016 |
| Cockerton Pizza Limited | Hospitality | 2024 |
| Code Monkeys Manchester Ltd | Information & communication | 2017 |
| Codeok Ltd | Wholesale & retail | 2025 |
| Coglan Cleaner Windows Ltd | Administrative & support | 2023 |
| Cognizant Properties Limited | Real estate | 2019 |
| Cojocariutransport Limited | Wholesale & retail | 2024 |
| COLLECT22 Ltd | Administrative & support | 2023 |
| Collectors GEM House Ltd | Wholesale & retail | 2022 |
| College Court Owners Limited | Households | 1980 |
| Collin & Co. Limited | Health & social care | 2013 |
| Collingwood Coffee Co. Limited (the) | Administrative & support | 1975 |
| Columbus Cleaning Machines (North East) Limited | Wholesale & retail | 2006 |
| Columbus Vehicle Wash Recycling Ltd | Manufacturing | 2016 |
| Combined Property Ltd | Real estate | 2018 |
| Comet Catering Ltd | Hospitality | 2012 |
| Commercial Electrical Contractors Ltd | Construction | 2025 |
| Commercial Vehicle Cleaners Limited | Other services | 2004 |
| Commercial Yard Management Company Limited | Households | 2004 |
| Communicators Training Associates Holdings Limited | Financial services | 2022 |
| Communicators Training Associates Limited | Professional & scientific | 2001 |
| Compact Services N.E. Ltd | Construction | 2008 |
| Competition Line (U.K.) Limited | Arts & recreation | 1982 |
| Compiled Social Limited | Information & communication | 2021 |
| Complete Home Inspections Guaranteed Limited | Construction | 2024 |
| Complete Property NE Ltd | Real estate | 2024 |
| Complete Roofs and Drives Ltd | Construction | 2023 |
| Complete Security Systems Limited | Administrative & support | 2019 |
| Computerise Limited | Information & communication | 1997 |
| CON Mech Group Limited | Manufacturing | 1949 |
| CON Mech Holdings Limited | Financial services | 2019 |
| Concept Quality Services Ltd | Professional & scientific | 2010 |
| Concord Consultancy Services Ltd | Information & communication | 2017 |
| Conducting Ltd | Information & communication | 2022 |
| Conduit Trade Partners Ltd | Administrative & support | 2026 |
| Conner Richardson Limited | Construction | 2024 |
| Connor Beasley Ltd | Arts & recreation | 2025 |
| Conservative Friends of Canzuk Ltd | Other services | 2024 |
| Consilium Bespoke Ltd | Professional & scientific | 2021 |
| Constantine Court (Middlesbrough) RTM Company Limited | Households | 2008 |
| Constellation Financial Services Limited | Extraterritorial | 2015 |
| Contract Associates Limited | Wholesale & retail | 2020 |
| Contract Flooring Services (North East) Limited | Construction | 1986 |
| Conway Properties Group Ltd | Real estate | 2026 |
| Coohmatd Ltd | Wholesale & retail | 2025 |