| City Skyline Properties Ltd | Administrative & support | 2015 |
| City West Management Limited | Real estate | 2002 |
| Citylets & Developments Ltd | Real estate | 2011 |
| Citymark Property Ltd | Real estate | 2026 |
| Civil Engineering Contractors Association (North East) Limited | Other services | 1996 |
| CJ Premises Ltd | Households | 2025 |
| CJ Scaffolding NE Ltd | Construction | 2023 |
| CJB Domestic GAS Services Ltd | Construction | 2016 |
| Cjcc Property Development Ltd | Construction | 2024 |
| CJG Repairs Limited | Manufacturing | 2021 |
| CJH Geotechnical Limited | Professional & scientific | 2023 |
| CJK Building Limited | Construction | 2021 |
| CJP Catering Services Ltd | Hospitality | 2026 |
| CJS Estates Limited | Real estate | 2012 |
| CK & SON Property Maintenance Limited | Construction | 2016 |
| CK Air-Conditioning and Services Limited | Construction | 2025 |
| CK Hire Limited | Administrative & support | 2025 |
| Ckarma Limited | Real estate | 2025 |
| CKS Grocery Ltd | Wholesale & retail | 2023 |
| CKW (Europe) Limited | Wholesale & retail | 2018 |
| CL Paving & Landscaping Limited | Administrative & support | 2025 |
| Cladwise Bathrooms Limited | Wholesale & retail | 2017 |
| Claim IT! Ltd | Administrative & support | 2005 |
| Claim Your Funding Ltd | Construction | 2018 |
| Claire Morgan Studio Ltd | Arts & recreation | 2013 |
| Clapham Bayis Limited | Real estate | 2021 |
| Clapham Binyan Limited | Real estate | 2023 |
| Claremont Joinery North East Limited | Construction | 2009 |
| Clarendon Management Services Ltd | Professional & scientific | 2015 |
| Clarice Carr and Company Ltd | Real estate | 2018 |
| Clarice Property Group Ltd | Real estate | 2021 |
| Clarion Estates Limited | Real estate | 2025 |
| Clark Financial Consulting Services Ltd | Professional & scientific | 2016 |
| Clark Mezzanines Ltd | Manufacturing | 2003 |
| Classic Cathedral Holdings Ltd | Administrative & support | 2011 |
| Clayfield Limited | Wholesale & retail | 2026 |
| Clayton Perks Consulting Limited | Other services | 2012 |
| Clayton Street Apartments Limited | Real estate | 2016 |
| Clean Healthy Nutritious Limited | Hospitality | 2026 |
| Clean Sweep (North East) Limited | Administrative & support | 2013 |
| Clean Treats Co Limited | Wholesale & retail | 2025 |
| Cleaners for Causes Limited | Other services | 2011 |
| Cleaniq Co Solutions Ltd | Administrative & support | 2025 |
| Cleanix Limited | Administrative & support | 2020 |
| Cleans 4 Less Ltd | Other services | 2019 |
| Cleanse IT Limited | Administrative & support | 2020 |
| Clear Brew Newcastle Ltd | Administrative & support | 2020 |
| Clear Cost Utilities Limited | Financial services | 2022 |
| Clearly Digital North East Limited | Construction | 2019 |
| Clearvue.Business Holdings Limited | Financial services | 2018 |
| Clearvue.Business Limited | Wholesale & retail | 2018 |
| Clennell Properties Limited | Real estate | 1996 |
| Cleveland Medical Services LLP | | 2020 |
| Clicq Ltd | Information & communication | 2025 |
| Clifford MBY Ltd | Health & social care | 2007 |
| Clifton Hall Development Ltd | Construction | 2025 |
| Clifton Hall Lofts Ltd | Construction | 2025 |
| Clinch Medical Services Ltd | Health & social care | 2025 |
| Clinic 17 Ltd | Other services | 2024 |
| CLK Treatments Ltd | Other services | 2025 |
| Clockmill MOT & Mechanical Services Ltd | Wholesale & retail | 2024 |
| Cloud Courier Services Ltd | Transport & logistics | 2025 |
| Cloud Nine Collective Limited | Other services | 2018 |
| Cloud Realty Ltd | Real estate | 2020 |
| CLOUD9WORLDUK Limited | Education | 2022 |
| CLR (East Boldon) Limited | Wholesale & retail | 2002 |
| CLR Law Limited | Professional & scientific | 2010 |
| Cluarantonn Ltd | Information & communication | 2024 |
| Clydepar Ltd | Real estate | 2017 |
| CM and Sons (NE) Limited | Administrative & support | 2024 |
| CM Roofing and Spec Cladding Ltd | Construction | 2026 |
| CMA Ltd | Wholesale & retail | 2022 |
| CMC North East Ltd | Wholesale & retail | 2005 |
| CMD 2018 Limited | Real estate | 2018 |
| Cmile Ltd | Education | 2024 |
| CMJ Project Services Limited | Professional & scientific | 2009 |
| CMR Delivery Ltd | Transport & logistics | 2026 |
| CMS Holdings UK Limited | Financial services | 2005 |
| CMS Pharm Ltd | Wholesale & retail | 2022 |
| Cmwalkersfuneralservices Ltd | Other services | 2014 |
| CMX Runway Ltd | Information & communication | 2018 |
| CNA Developments (NE) Ltd | Construction | 2017 |
| Cnhelmark Geotechnical Limited | Construction | 2013 |
| CNM Solutions Ltd | Construction | 2025 |
| CNV 2018 Limited | Health & social care | 2018 |
| Coates Industrial Ltd | Manufacturing | 2026 |
| Coatsink Software Ltd | Information & communication | 2011 |
| Coble Marina Ltd | Real estate | 2020 |
| Cobweb Information (UK) Limited | Extraterritorial | 1998 |
| Cobweb Information Limited | Information & communication | 2001 |
| Cockton Hill Limited | Wholesale & retail | 2016 |
| Cocolowe Limited | Administrative & support | 2016 |
| Codeifi Limited | Information & communication | 2017 |
| Colin Stephenson Masonry Ltd | Construction | 2022 |
| COLLABOR8 NE Ltd | Real estate | 2025 |
| Collective Design I D Limited | Professional & scientific | 2014 |
| Collective Hub Limited | Administrative & support | 2024 |
| Collective Impact Agency CIC | Professional & scientific | 2019 |
| Collings Retrofit Ltd | Construction | 2025 |
| Collingwood Immigration Services LLP | | 2014 |