| Cookfields Limited | Wholesale & retail | 2011 |
| Cooking House 123 Ltd | Hospitality | 2023 |
| Cookridge Hall Health & Fitness Limited | Arts & recreation | 2011 |
| Cool Move Mario Recruitment Ltd | Administrative & support | 2019 |
| Cool Move Mario Transport Ltd | Transport & logistics | 2019 |
| Coombe Homes Limited | Real estate | 2025 |
| Coopers Blinds & Shutters Ltd | Manufacturing | 2025 |
| Copeland Farms Limited | Agriculture & fishing | 2014 |
| Copeland Property Limited | Hospitality | 2006 |
| Copper Beech Darlington Ltd | Hospitality | 2026 |
| Copper Beech PUB Darlington Limited | Hospitality | 2024 |
| Corby Lodge (Norton) Management Company Limited | Households | 2003 |
| Core Club Ltd | Other services | 2018 |
| Core Psychology Limited | Health & social care | 2013 |
| Corner's Bulk Transport Limited | Transport & logistics | 2013 |
| Corners Transport Limited | Transport & logistics | 2024 |
| Cornerstone Enterprises Group Ltd | Other services | 2026 |
| Cornichon Hall Ltd | Financial services | 2024 |
| Cornucopia Investments Limited | Financial services | 2013 |
| Coronation 663 Ltd | Wholesale & retail | 2017 |
| Corporate Innovative Management Limited | Professional & scientific | 2000 |
| Corporate Personal Fitness Limited | Arts & recreation | 2015 |
| Corporate Personal Wellbeing Limited | Health & social care | 2019 |
| COS Systems Ltd | Administrative & support | 2009 |
| Cosmo Store Ltd | Information & communication | 2025 |
| Cost Control Consulting Ltd | Other services | 2021 |
| Costy Speditions Ltd | Transport & logistics | 2018 |
| Cotswolds Management Services Limited | Construction | 2013 |
| Cotterhill (EJB) Limited | Extraterritorial | 2024 |
| Cotterhill (GM) Limited | Extraterritorial | 2024 |
| Cotterhill (NLM) Limited | Extraterritorial | 2024 |
| Cotterhill (WM) Limited | Extraterritorial | 2024 |
| Cotterhill Limited | Wholesale & retail | 2000 |
| Coulby Joinery Ltd | Construction | 2024 |
| Coulter Holdings Limited | Administrative & support | 2019 |
| Country Harvest Frozen Foods Limited | Hospitality | 1991 |
| Countryman Estates Ltd | Hospitality | 2012 |
| County Groundworks Limited | Construction | 2019 |
| Couriersafe Ltd | Transport & logistics | 2020 |
| Courtney World Music Ltd | Information & communication | 2015 |
| Coutydseao Ltd | Wholesale & retail | 2026 |
| Cover New Homes Recruitment Ltd | Administrative & support | 2014 |
| Coverdale Hughes Ltd | Real estate | 2017 |
| Coverstone Coatings Ltd | Construction | 2025 |
| Covtec Limited | Manufacturing | 2007 |
| Cowclose Farm (Darlington) Limited | Agriculture & fishing | 2015 |
| Cowgreen Ltd | Wholesale & retail | 2022 |
| Cowie Consulting Limited | Professional & scientific | 2014 |
| Cowlam QC Limited | Administrative & support | 2023 |
| Cpra Ltd | Health & social care | 2015 |
| CR Roofing & Cladding NE Ltd | Construction | 2022 |
| CRA Consultancies Ltd | Professional & scientific | 2023 |
| Craftgrange Limited | Manufacturing | 1980 |
| Craig Colegrove Roofing & Cladding Ltd | Construction | 2013 |
| Crane PAD Solutions UK Ltd | Wholesale & retail | 2026 |
| Crannpath Consulting Ltd | Professional & scientific | 2025 |
| Cravers Fast Food Limited | Hospitality | 2020 |
| Create and Paint Limited | Wholesale & retail | 2016 |
| Creative HI Tech Limited | Wholesale & retail | 2016 |
| Crescent Guardians Ltd | Extraterritorial | 1997 |
| CRG Servicesv Limited | Transport & logistics | 2018 |
| Cricstarz Ltd | Wholesale & retail | 2020 |
| Crocodile Leisure Limited | Arts & recreation | 1992 |
| Croft Circuit Limited | Extraterritorial | 1982 |
| Croft Compliance Consultancy Limited | Administrative & support | 2007 |
| Croft Energy Consultancy Ltd | Professional & scientific | 2021 |
| Croft Entertainment Ltd | Information & communication | 2021 |
| Cross Keys Gainford Ltd | Hospitality | 2024 |
| Cross Media Group Ltd | Information & communication | 2013 |
| Crown Alderney Limited | Construction | 2009 |
| Crown Aquisitions Ltd | Administrative & support | 2023 |
| Crown Guthries Limited | Transport & logistics | 1974 |
| Crown Property Renovations Ltd | Construction | 2018 |
| Crsteps Ltd | Information & communication | 2013 |
| Crystal Clean Hygiene Ltd | Other services | 2019 |
| Crystal Properties UK Ltd | Construction | 2009 |
| Crystal-Tee (UK) Ltd. | Wholesale & retail | 2025 |
| Crystelle Limited | Wholesale & retail | 2017 |
| CS Nails & Spa Limited | Other services | 2025 |
| CSM Bolting Ltd | Construction | 2025 |
| CSS Electrical Ltd. | Energy | 2012 |
| CT Motor Sales Limited | Wholesale & retail | 2026 |
| CT Operations Ltd | Professional & scientific | 2015 |
| CT Roofing and Cladding Ltd | Construction | 2024 |
| CTA Holdings Limited | Financial services | 2022 |
| CTC Leisure Ltd | Hospitality | 2025 |
| CTF Riding Academy Ltd | Education | 2026 |
| Ctnl Ltd | Wholesale & retail | 2026 |
| Cuisine Marmaris Takeaway Ltd | Hospitality | 2024 |
| Cumbria & Borders Adaptations Ltd | Manufacturing | 2017 |
| Cummins UK Pension Plan Trustee Limited | Professional & scientific | 1999 |
| Cupla Ltd | Real estate | 2018 |
| Curo Marketing Ltd | Professional & scientific | 2009 |
| Curren Consulting Ltd | Professional & scientific | 2025 |
| Curry K Darlington Ltd | Hospitality | 2026 |
| Customplatesuk Ltd | Wholesale & retail | 2025 |
| Cuthbert Power Solutions Ltd | Manufacturing | 2025 |
| CV Living Ltd | Construction | 2026 |
| CVL Ltd | Transport & logistics | 2026 |
| CW Fitness Coach Ltd | Other services | 2023 |