| C Hewison. Consultant, Project Management, Training Ltd. | Education | 2015 |
| C L & E Holdings Limited | Professional & scientific | 2018 |
| C. Mckie & Associates Ltd | Professional & scientific | 2016 |
| C.A.M Automation Ltd | Manufacturing | 2013 |
| Cactuspizzeria Limited | Hospitality | 2026 |
| Cairn Hunter Limited | Information & communication | 2026 |
| Caledonia Propertise Limited | Real estate | 2025 |
| Cambridge Law Studio Limited | Education | 1999 |
| Canford Trustee Limited | Other services | 2019 |
| Canny Inns Ltd | Hospitality | 2016 |
| Canny Investments Limited | Hospitality | 2018 |
| Capelli Hair Design Corbridge Ltd | Other services | 2011 |
| Capital UK Electrics Ltd | Construction | 2012 |
| Carbon ARC Training and Consultancy Limited | Professional & scientific | 2020 |
| Carbon Index Ltd | Professional & scientific | 2024 |
| Carbon Zero Futures Ltd | Professional & scientific | 2024 |
| Care Farm Trust | Agriculture & fishing | 2009 |
| Carifo Investment Ltd | Real estate | 2018 |
| Carliol Holdings Ltd | Financial services | 2018 |
| Carlyle COM HEM Follow-On Partners I, L.P. | | 2010 |
| Carlyle COM HEM Follow-On Partners II, L.P. | | 2010 |
| Carlyle Foundry Partners, L.P. | | 2011 |
| Carlyle Numericable Partners I, L.P. | | 2008 |
| Carlyle Numericable Partners II, L.P. | | 2008 |
| Carole Loader Limited | Professional & scientific | 2013 |
| Carr House Electrical Ltd | Administrative & support | 2016 |
| Carruthers Electrical OIL & GAS Limited | Professional & scientific | 2014 |
| Carter Family Holdings Limited | Financial services | 2019 |
| Case International, LLC | | 2019 |
| Caspian Policy Centre | | 2022 |
| Castle Kindergarten Ltd | Education | 2016 |
| Castlemead Homecraft Limited | Construction | 2004 |
| Ccia UK | | 2024 |
| Cctv (NE) Ltd | Administrative & support | 2015 |
| CDC Green Limited | Hospitality | 2025 |
| CDM Safety Solutions Limited | Professional & scientific | 2015 |
| CDR Motors Ltd | Wholesale & retail | 2024 |
| Cellular Rental Services Limited | Information & communication | 1987 |
| Centriseal Limited | Professional & scientific | 2013 |
| Centurion Properties Limited | Real estate | 2024 |
| Century Composites Limited | Manufacturing | 1978 |
| CEP III AIV Z, L.P. | | 2009 |
| CEP IV Dollar Feeder, L.P. | | 2013 |
| CEP IV Managing GP, L.P. | | 2013 |
| CFM GAS, Plumbing and Heating Ltd | Construction | 2024 |
| CFM Property Group Ltd | Real estate | 2026 |
| CG Engineering Services Limited | Professional & scientific | 2016 |
| Cgconsultedu Limited | Education | 2018 |
| Chainbridge Steel (North East) Ltd | Wholesale & retail | 1999 |
| Chainbridge Steel Group Limited | Wholesale & retail | 2006 |
| Chair Benders Ltd | Education | 2025 |
| Chambers Productions Incorporated Ltd | Manufacturing | 2021 |
| Chameleon Vocational Training Limited | Education | 2012 |
| Champs Washington Limited | Hospitality | 2020 |
| Channel 11 Limited | Arts & recreation | 2020 |
| Charlton Engineering Services Limited | Manufacturing | 2000 |
| Chartershaugh Technical Services Limited | Professional & scientific | 2023 |
| Chase Mobile Radio Limited | Information & communication | 1986 |
| Cheeky Chimps Childcare Limited | Education | 2024 |
| Chef's Kiss Creative Limited | Arts & recreation | 2025 |
| Chemelex (UK) Limited | Manufacturing | 1999 |
| Chemelex Holding UK Ltd | Financial services | 2024 |
| Cherry Blossom North East Limited | Hospitality | 2025 |
| Cherry Tree Washington Limited | Hospitality | 2019 |
| Cheryl Darcy Ltd | Professional & scientific | 2025 |
| Chevron Properties LLC | | 2024 |
| Child and Adolescent Behaviour Services Limited | Health & social care | 2023 |
| Chmg Property Ltd | Real estate | 2025 |
| Choice Wellbeing Service CIC | Health & social care | 2023 |
| Chris Lund Enterprises Limited | Wholesale & retail | 1991 |
| Civicus: World Alliance for Citizen Participation, Inc. | | 2002 |
| CJM Engineering Services Limited | Professional & scientific | 2016 |
| Cklip Ltd | Administrative & support | 2014 |
| Clarabells Deli and Pizzeria Limited | Hospitality | 2024 |
| Clark Pharma Diagnostics Ltd | Wholesale & retail | 2023 |
| Clas Consultancy Limited | Financial services | 2021 |
| Clay's Garden Centre Ltd. | Wholesale & retail | 2001 |
| Cleaning Solutions Northeast Ltd | Administrative & support | 2021 |
| Clear Buy 2 LET Limited | Financial services | 2016 |
| Cleer Solutions Limited | Transport & logistics | 2018 |
| Cleverflow Limited | | 1990 |
| Client and Cloud Ltd | Professional & scientific | 2025 |
| Clifton Stores Limited | Wholesale & retail | 2010 |
| Climate Action Sunderland Community Interest Company | Education | 2024 |
| Clothing for Work Mandate by Mags Ltd | Manufacturing | 2015 |
| CLR Fixings Ltd | Wholesale & retail | 2014 |
| CM Cyber Solutions Ltd | Information & communication | 2023 |
| Cmcr Consulting Ltd | Information & communication | 2024 |
| Co Procurement Ltd | Administrative & support | 2022 |
| CO2EFFICIENT Limited | Professional & scientific | 2011 |
| Coded North Ltd | Information & communication | 2024 |
| Coffee Design (London) Limited | Extraterritorial | 2013 |
| Collega Ltd | Other services | 2024 |
| Colour Coats NE Limited | Construction | 2023 |
| Columbia Cosy Cafe CIC | Hospitality | 2025 |
| Comconnect Limited | Construction | 2018 |
| Commercial and SME Management Ltd | Energy | 2022 |
| Communication Spares (U.K.) Limited | Information & communication | 1991 |
| Complete Maintenance Solutions Limited | Manufacturing | 2008 |
| Compliance Services International Consultants LLC | | 2000 |