| Combi Care North East Limited | Construction | 2008 |
| Communigate Autism Limited | Health & social care | 2023 |
| Community Minds CIC | Health & social care | 2021 |
| Comprehensive Quality Inspection Ltd. | Professional & scientific | 2010 |
| Confluence Living CIC | Information & communication | 2026 |
| Connected Coaching NE Ltd | Education | 2021 |
| Connectvips Ltd | Administrative & support | 2018 |
| Connexions for Ever Ltd | Public administration | 2019 |
| Conservatory Sales Limited | Construction | 2021 |
| Consilience Media Limited | Information & communication | 2001 |
| Contention Ltd | Information & communication | 2014 |
| Contour Blinds Ltd | Manufacturing | 2010 |
| Cooke & Co Residential Lettings Limited | Real estate | 2012 |
| Cooks Joinery & Home Improvements Ltd | Construction | 2019 |
| Cooper Edwards Group Limited | Administrative & support | 2017 |
| Cooper Edwards Holdings Limited | Real estate | 2021 |
| Cooperfam Ltd | Real estate | 2025 |
| Coopers North East Ltd | Wholesale & retail | 2024 |
| Coquet Housekeeping Ltd | Administrative & support | 2025 |
| Corze Property Ltd | Real estate | 2024 |
| Costas Trading Ltd | Wholesale & retail | 2022 |
| Cottage Rest Homes Limited | Extraterritorial | 1979 |
| Cottam & Co Limited | Real estate | 2007 |
| Cradan Partners Limited | Professional & scientific | 2025 |
| Craig S Dixon Ltd | Construction | 2020 |
| Craigmont Court (Benton) RTM Management Company Limited | Households | 2009 |
| Craigmore Gardens Ltd | Administrative & support | 2024 |
| Craigmore Landscaping Ltd | Administrative & support | 2025 |
| Crank Destroyers Limited | Arts & recreation | 2021 |
| Craven Commercial Limited | Real estate | 2025 |
| Creating Monsters Limited | Information & communication | 2013 |
| Creative Cabin Drama Ltd | Education | 2024 |
| Creed North Limited | Real estate | 2017 |
| Crest Education Training Ltd | Education | 2026 |
| Crosby Hire Limited | Hospitality | 2016 |
| Crosby Loves Cheese Ltd | Wholesale & retail | 2019 |
| Crossgate Mews (Durham) Management Company Limited | Households | 2003 |
| Crowds Hair Limited | Other services | 2019 |
| Crowe Humble Wesencraft LLP | | 2023 |
| Crusader Fire (Northern) Limited | Manufacturing | 2004 |
| CT E & I Ltd | Construction | 2026 |
| CT Plant Services Limited | Professional & scientific | 2025 |
| Cubebase Ltd | Information & communication | 2024 |
| Cullercoats Bike & Kayak Adventures Ltd | Wholesale & retail | 2023 |
| Cullercoats Family Chiropractic Limited | Health & social care | 2013 |
| Cullingford Henry Limited | Financial services | 2025 |
| Cultiviq Ltd | Professional & scientific | 2025 |
| Cultura HR Limited | Professional & scientific | 2018 |
| Cummings Consulting Group Limited | Professional & scientific | 2025 |
| Curate Creative Ltd | Professional & scientific | 2016 |
| Curry Property Solutions Ltd | Real estate | 2026 |
| CX Fitness Ltd | Wholesale & retail | 2016 |
| Cyberex Ltd | Information & communication | 2024 |
| Cycling Performance Limited | Other services | 2019 |
| CYD Consultants Ltd | Professional & scientific | 2024 |
| Cyit Ltd | Information & communication | 2009 |
| D & G Motors Limited | Wholesale & retail | 2007 |
| D and H PYE Properties Ltd | Real estate | 2019 |
| D R Property Holdings Limited | Real estate | 2019 |
| D Wood Management Ltd | Construction | 2014 |
| D.P. Marketing Limited | Professional & scientific | 2002 |
| D12 Highbury Ltd | Real estate | 2019 |
| D12 Software Solutions Limited | Information & communication | 2009 |
| DAD2 Limited | Wholesale & retail | 2025 |
| Daiser Ltd | Information & communication | 2024 |
| Dakota Food and Coffee Ltd | Hospitality | 2018 |
| Dallas Carpets Limited | Wholesale & retail | 1976 |
| Damian Oldham Consultant Ltd | Information & communication | 2020 |
| Danconmil Services Limited | Professional & scientific | 2024 |
| Dannah Design Limited | Manufacturing | 2023 |
| Danni Limited | Health & social care | 2005 |
| Darren Byers Ltd | Other services | 2014 |
| Darvall Developments Limited | Real estate | 2020 |
| DAS Projects Ltd | Manufacturing | 2026 |
| Data United Ltd | Information & communication | 2013 |
| Datechnical Limited | Arts & recreation | 2016 |
| Davanti Classico Limited | Hospitality | 2018 |
| Davanti Tynemouth Limited | Hospitality | 2018 |
| David James Geotechnical Ltd | Professional & scientific | 2021 |
| Davtec Energy Ltd | Professional & scientific | 2025 |
| Daycool Limited | Extraterritorial | 1997 |
| DB Holdings Limited | Real estate | 2015 |
| Dboyzncl Limited | Wholesale & retail | 2025 |
| DC Services (Hartlepool) Limited | Construction | 2023 |
| Dcan Limited | Professional & scientific | 2011 |
| DDS Consulting Ltd | Professional & scientific | 2022 |
| Dealerway Ltd | Wholesale & retail | 2023 |
| Deborah Green Jewellers Ltd | Wholesale & retail | 2007 |
| Decke Contracts Limited | Construction | 2018 |
| Decorit Associates Limited | Wholesale & retail | 2023 |
| Decote Dance Ltd | Arts & recreation | 2014 |
| Decote Dancewear Ltd | Wholesale & retail | 2017 |
| Deep Breath Running Ltd | Health & social care | 2023 |
| DEL Avante Properties Ltd | Real estate | 2017 |
| Delaval Barber Ltd | Other services | 2024 |
| Delaval Equestrian Limited | Other services | 2014 |
| Delivering With Purpose Ltd | Real estate | 2021 |
| Delivery Corner Ltd | Hospitality | 2016 |
| Delta Capital Property Investment Limited | Real estate | 2023 |
| Delta HV Services Ltd | Construction | 2018 |