| Cleveland Carpet Services Limited | Wholesale & retail | 2011 |
| Cleveland Conservatories Ltd | Construction | 2002 |
| Cleveland Doors Limited | Manufacturing | 2019 |
| Cleveland Engineering Developments Limited | | 1995 |
| Cleveland Foods | | 1989 |
| Cleveland Geomatics Limited | Professional & scientific | 2016 |
| Cleveland Grab Services Ltd | Administrative & support | 2010 |
| Cleveland Gynaecology and Fertility Centre Limited | Health & social care | 2010 |
| Cleveland Hearing Services Limited | Professional & scientific | 2021 |
| Cleveland Holdings Investment Ltd | Real estate | 2017 |
| Cleveland Landscaping Ltd | Administrative & support | 2023 |
| Cleveland Legal Services Ltd | Professional & scientific | 2021 |
| Cleveland Leisure Centres Limited | Arts & recreation | 1973 |
| Cleveland Models Limited | Wholesale & retail | 2009 |
| Cleveland Property Limited | Construction | 2012 |
| Cleveland Renovations Ltd | Construction | 2024 |
| Cleveland Safety & Training Ltd | Professional & scientific | 2023 |
| Cleveland Scientific Institution | Professional & scientific | 1923 |
| Cleveland Security Limited | Administrative & support | 2003 |
| Cleveland Sitesafe Limited | Manufacturing | 1987 |
| Cleveland Stores Ltd | Wholesale & retail | 2017 |
| Cleveland Synthetic Maintenance Limited | Administrative & support | 2018 |
| Cleveland Timber Supplies Limited | Manufacturing | 1976 |
| Cleveland Trade Ltd | Wholesale & retail | 2024 |
| Cleveland UP & Over Doors Limited | Professional & scientific | 2003 |
| Cleveland Vehicle Sales Ltd. | Wholesale & retail | 2020 |
| Cleveland Windows and Doors Limited | Extraterritorial | 2014 |
| Clichy Estates Ltd | Real estate | 2026 |
| Click Bazzar Ltd | Wholesale & retail | 2026 |
| Clicktodrop Ltd | Transport & logistics | 2025 |
| Clickway Commerce Limited | Wholesale & retail | 2026 |
| Client Acquisition Labs Ltd | Professional & scientific | 2024 |
| Climate Solutions Exchange Limited | Agriculture & fishing | 2020 |
| Clinicabin Ltd | Construction | 2020 |
| Clinical Capsules Ltd | Education | 2025 |
| Clinkard Holdings Limited | Financial services | 2023 |
| Clive Road NE Ltd | Wholesale & retail | 2026 |
| CLM Projects UK Ltd | Construction | 2024 |
| CLM Recruitment UK Ltd | Administrative & support | 2024 |
| Close Granger Gray & Wilkin Consultancy Limited | Professional & scientific | 1992 |
| Close Vehicle Rental Ltd | Administrative & support | 2018 |
| Clothing Connect Ltd | Wholesale & retail | 2025 |
| Cloud Crafter Developer Limited | Information & communication | 2025 |
| Clouddict Ltd | Administrative & support | 2025 |
| Cloudview Media Ltd | Administrative & support | 2025 |
| Cloudway Ventures Ltd | Hospitality | 2025 |
| Clovenden Limited | Professional & scientific | 2025 |
| Clover Group North East Ltd | Health & social care | 2023 |
| Clover Support Limited | Health & social care | 2025 |
| Cltm Properties Ltd | Real estate | 2025 |
| Clutch and Gearbox Ltd | Manufacturing | 2025 |
| CLW Properties NE LLP | | 2026 |
| CM Groundworks and Landscaping Ltd | Construction | 2021 |
| CM Scaffolding Ltd | Construction | 2026 |
| CM Todd Ltd | Professional & scientific | 2024 |
| CMC Services Limited | Other services | 2017 |
| CMJ Rigging & Lifting Ltd | Administrative & support | 2017 |
| CMM Wind Limited | Construction | 2025 |
| CMP (Wakefield) Limited | Wholesale & retail | 2019 |
| Cmtc Holdings Limited | Professional & scientific | 2024 |
| CNB Couriers Ltd | Transport & logistics | 2021 |
| CNC Properties NE Ltd | Households | 2025 |
| CNC Recycling Limited | Wholesale & retail | 2018 |
| CNG Management Services Ltd | Professional & scientific | 2024 |
| CNL Stokesley Ltd | Administrative & support | 2019 |
| CNS Construction North East Limited | Construction | 2015 |
| CNY Rigging Services Limited | Construction | 2025 |
| Co and Co Group Limited | Hospitality | 2026 |
| Co Enforcement Services Limited | Administrative & support | 2014 |
| Co-Working Thursdays CIC | Administrative & support | 2024 |
| Coaching by Chris Ltd | Arts & recreation | 2021 |
| Coakes and Coulson Associates Ltd | Construction | 2009 |
| Coastal Decorating Services Limited | Construction | 2014 |
| Coastal Property Solutions Ltd | Construction | 2025 |
| Coastland Global Limited | Wholesale & retail | 2026 |
| Coaz Builders Limited | Construction | 2022 |
| Cobalt Machinery Limited | Manufacturing | 2023 |
| Cobra Cabling Solutions Ltd | Information & communication | 2023 |
| Cobra Controls Limited | Information & communication | 2016 |
| Cobra Middlesbrough Limited | Transport & logistics | 1999 |
| Cochranes Padel Club Limited | Arts & recreation | 2025 |
| Cockfield, Knight & Company Limited | Transport & logistics | 2010 |
| Cockle Marine Ltd | Transport & logistics | 2019 |
| Coco & RUM Mbro Ltd | Hospitality | 2023 |
| Coco Foods Limited | Hospitality | 2024 |
| Coco's Beauty Ltd | Other services | 2017 |
| Cocotours Ltd | Administrative & support | 2023 |
| Codale Limited | Construction | 2020 |
| Codewise IT Services Limited | Information & communication | 2026 |
| Codyia Ltd | Information & communication | 2026 |
| COE Transport UK Ltd | Transport & logistics | 2025 |
| Coeus Software Limited | Information & communication | 2006 |
| Cognitive Healthtech Ltd | Information & communication | 2024 |
| Cognoscenti Developments Limited | Construction | 2018 |
| Cohost Ltd | Real estate | 2023 |
| Colannino Design Limited | Professional & scientific | 2013 |
| Colathon Diagnostics and Clinical Services Limited | Health & social care | 2025 |
| Colclough Engineering Limited | Real estate | 2010 |
| Cold Hill Ltd | Professional & scientific | 2025 |
| Coldtech Refrigeration & Air Conditioning Ltd | Construction | 2015 |