| Coco Falcons Ltd | Agriculture & fishing | 2021 |
| Cocoon Trading Limited | Manufacturing | 1999 |
| Coffee and KIN Ltd | Wholesale & retail | 2016 |
| Coho Life Limited | Manufacturing | 2018 |
| Coke Turner & Co Limited | Administrative & support | 2009 |
| Colourart Limited | Construction | 2018 |
| Command and Control Consultants Limited | Information & communication | 2012 |
| Commercial Leadership Solutions Ltd | Professional & scientific | 2026 |
| Complete Business Supplies Limited | Manufacturing | 2008 |
| Compycraft Ltd | Other services | 2022 |
| Conolly Consulting Ltd | Administrative & support | 2008 |
| Construction Consulting Solutions Ltd | Professional & scientific | 2021 |
| Copperfield Alnwick Ltd | Hospitality | 2025 |
| Coquet Moor Caravan Park Limited | Hospitality | 2017 |
| Costa Skin Limited | Wholesale & retail | 2021 |
| Cottage Inn Craster Ltd | Hospitality | 2026 |
| Countryside Cleaning Ltd | Administrative & support | 2025 |
| Countryside Collection Ltd | Hospitality | 2025 |
| Craig Connor Property Investments Limited | Real estate | 2026 |
| Craster Fishermen Harbour Company Limited | Agriculture & fishing | 1980 |
| Craster South Farm Company Limited | Households | 2017 |
| Creatively Conscious Ltd | Education | 2024 |
| Creel & Reel Limited | Hospitality | 2021 |
| CRJ (NE) Ltd | Other services | 2016 |
| Croft Place Roadway Management Limited | Households | 2016 |
| Crystal Scientific (UK) Limited | Professional & scientific | 1995 |
| Csserve Limited | Other services | 2025 |
| CTJ Moore Ltd | Mining & quarrying | 2025 |
| Culture Creative Limited | Professional & scientific | 2005 |
| Cultured Food & Drinks Ltd | Hospitality | 2024 |
| Cussins (North East) Limited | Construction | 2000 |
| Cussins Limited | Professional & scientific | 2014 |
| Custom Homes Ltd | Construction | 2022 |
| D.F.Calder Farms Limited | Agriculture & fishing | 1960 |
| Damian Cruden Creative Limited | Arts & recreation | 2011 |
| Dansformation CIC | Arts & recreation | 2024 |
| Darklight Event Services Ltd | Professional & scientific | 2022 |
| David Richard Wynne Limited | Arts & recreation | 2017 |
| Davidson Timber UK Limited | Wholesale & retail | 2006 |
| Davies Electrical Services Ltd | Construction | 2024 |
| Daytripper Print & Design Limited | Manufacturing | 2016 |
| DBK Analytics Ltd | Information & communication | 2023 |
| Deb-It Accountancy Limited | Professional & scientific | 2023 |
| Delivering Differently Limited | Professional & scientific | 2019 |
| Dennis Enterprises UK Limited | Real estate | 2026 |
| Dent-Pro N.E Ltd | Wholesale & retail | 2019 |
| Denwick Court (Management Company) Limited | Households | 2003 |
| Denwick Joinery & Building Contractors Limited | Construction | 2004 |
| Denwick Lane END Management Company Limited | Real estate | 2005 |
| DESK101 Limited | Administrative & support | 2022 |
| DFI Holdings Ltd | Financial services | 2023 |
| DG Technology Solutions Ltd | Information & communication | 2018 |
| DGT Properties Limited | Real estate | 2024 |
| DI Sopra Limited | Hospitality | 2015 |
| Dinguardi Limited | Real estate | 2025 |
| Doole Building Ltd | Other services | 2025 |
| Dovecote Northumberland Ltd | Manufacturing | 2023 |
| Doxford Barns Ltd | Hospitality | 2021 |
| Doxford Farm Cottages Ltd | Hospitality | 2018 |
| DR Y Chan Limited | Health & social care | 2013 |
| Dreamgirlz Hair Extensions Limited | Other services | 2016 |
| DRJ Access Limited | Manufacturing | 2019 |
| Drone AG Limited | Agriculture & fishing | 2015 |
| Dronsfield Properties Limited | Households | 2020 |
| DRU Allan Design Ltd | Administrative & support | 2016 |
| Drwraggdeliveries Limited | Transport & logistics | 2023 |
| DS2 Management Consultancy Ltd | Extraterritorial | 2020 |
| Dselec Limited | Construction | 2024 |
| Dunbar Bayswell Ltd | Hospitality | 2012 |
| Dunstan Holdings Limited | Real estate | 2019 |
| Dunstanburgh Castle Golf Course Limited | Arts & recreation | 2022 |
| Dunstanburgh Farm Limited | Agriculture & fishing | 1997 |
| Durham Hotel Investment Limited | Construction | 2008 |
| Dynamic Consultancy (NE) Ltd | Administrative & support | 2021 |
| E & T Farming Limited | Agriculture & fishing | 2017 |
| Earth Light Balance Limited | Extraterritorial | 2019 |
| Easy Move (NE) Ltd | Transport & logistics | 2008 |
| Easy Move Removals & Storage Ltd | Transport & logistics | 2024 |
| EB Bridal Ltd | Wholesale & retail | 2021 |
| EB Prom & Occasion Wear Ltd | Wholesale & retail | 2024 |
| Echobi Ltd | Information & communication | 2025 |
| Ecoparx Northumberland Ltd | Professional & scientific | 2024 |
| Elevatio Bidco Limited | Financial services | 2023 |
| Elevatio Topco Limited | Financial services | 2023 |
| Elifsu Limited | Real estate | 2024 |
| Ellingham Community Trust | Other services | 2012 |
| Elliston Fine Wines Limited | Wholesale & retail | 2003 |
| Embers North East Ltd | Hospitality | 2023 |
| Embleton Mill Ltd | Wholesale & retail | 2022 |
| Emergent Works Limited | Professional & scientific | 2014 |
| EMIR02 Ltd | Hospitality | 2023 |
| Emma Wardle (2011) Limited | Health & social care | 2011 |
| Emperorsnewmove Ltd | Real estate | 2021 |
| Energydirection Limited | Professional & scientific | 2012 |
| Enhance Beauty Rooms Limited | Other services | 2024 |
| Environmental Land Management Limited | Administrative & support | 2001 |
| Estuary View Caravans Limited | Hospitality | 2016 |
| Etech Training (UK) Limited | Information & communication | 2020 |
| Eveanna B&B LLP | | 2025 |
| Everything Music Ltd | Information & communication | 2020 |