| Classic Pizza Blyth 2 Ltd | Hospitality | 2026 |
| Cloud Integration Solutions Ltd | Information & communication | 2024 |
| CNE Interiors Ltd | Construction | 2026 |
| Coalescent Solutions Ltd | Information & communication | 2024 |
| Coastal Financial Services Limited | Financial services | 2011 |
| Coastal Interiors NE Ltd | Administrative & support | 2018 |
| Coastalcardsblyth Ltd | Wholesale & retail | 2025 |
| Coastline Fish and Chip Restaurant Limited | Hospitality | 2001 |
| Codeplex Limited | Information & communication | 2013 |
| Cole Charlton Property Limited | Real estate | 2025 |
| Collingwood Safety Ltd | Professional & scientific | 2016 |
| Colourdec Limited | Construction | 2005 |
| Compass Point North East Limited | Health & social care | 2015 |
| Complete Demolition and Reclamation Ltd | Construction | 2021 |
| Coms Wedding and Events Ltd | Hospitality | 2020 |
| Confidence Care and Support Limited | Health & social care | 2019 |
| Connect Northumberland | Other services | 2024 |
| Conolly Engineering Ltd | Manufacturing | 2018 |
| Copper Cars Ltd | Transport & logistics | 2023 |
| Coquet Dog Co. Ltd | Hospitality | 2025 |
| Core Mobile Limited | Information & communication | 2024 |
| Core Voice Limited | Information & communication | 2024 |
| Coreisp Group Limited | Information & communication | 2023 |
| Coreisp Network Services Limited | Information & communication | 2024 |
| Cornerstone Retail Ltd | Wholesale & retail | 2020 |
| Coseng Limited | Information & communication | 2020 |
| Coseng Properties Ltd | Real estate | 2025 |
| Coseng Techconsult Ltd | Information & communication | 2026 |
| Cotterill Heating and Plumbing Services Limited | Construction | 2017 |
| Cowie Property Limited | Real estate | 2022 |
| Cowpen House Limited | Hospitality | 2025 |
| Cowpen Quay Community Association | Arts & recreation | 2007 |
| CPH Psychological Services Ltd | Education | 2023 |
| Crcr Motor Group Ltd | Wholesale & retail | 2026 |
| Crosbtech Ltd | Professional & scientific | 2022 |
| Crosby & Smith Roofing Ltd | Construction | 2022 |
| CSR Renewable Ltd | Manufacturing | 2025 |
| Ctrl ALT Create Ltd | Wholesale & retail | 2026 |
| CTS North East Limited | Administrative & support | 2009 |
| Cuchi-Pa Limited | Arts & recreation | 2022 |
| Cuchihh Ltd | Wholesale & retail | 2022 |
| Cutters Salon Supplies Ltd | Wholesale & retail | 2013 |
| CW Consultancy (Worksop) Ltd | Construction | 2020 |
| D & D Armstrong Limited | Transport & logistics | 2003 |
| D & M Fencing Limited | Construction | 2001 |
| D D Drinks and Entertainment Ltd | Hospitality | 2024 |
| D Oliver Construction Ltd | Construction | 2025 |
| D Roberts Transport Ltd | Transport & logistics | 2023 |
| D&S Building & Property Maintenance (North East) Limited | Construction | 2018 |
| D'Or Pubs Limited | Hospitality | 2025 |
| D@R Roberts PUB Company Ltd | Hospitality | 2025 |
| Dali Air Ltd | Manufacturing | 2019 |
| Dalotech Marine Ltd | Professional & scientific | 2025 |
| Dave J Stone Ltd | Construction | 2022 |
| Dave Rees Consultancy Ltd | Professional & scientific | 2020 |
| Dave Rees Holdings Limited | Professional & scientific | 2018 |
| Davis E&I Limited | Construction | 2022 |
| DBC Process and Pipeline Services Ltd | Construction | 2023 |
| DC Marine Electronics Ltd | Manufacturing | 2026 |
| DCE Tiling Limited | Construction | 2020 |
| DCT Mechanical Ltd | Mining & quarrying | 2025 |
| Dczlc Ltd | Real estate | 2025 |
| Deen Barbers NE Ltd | Other services | 2024 |
| Deer IVY Limited | Wholesale & retail | 2022 |
| Dees Barbers Blyth Limited | Other services | 2025 |
| Defender Rigging Services Limited | Professional & scientific | 2017 |
| Delling SL Ltd | Administrative & support | 2025 |
| Derek Breezy Coaching Limited | Education | 2025 |
| Derek Reed Heating Services Limited | Construction | 2002 |
| Derive Ltd | Professional & scientific | 2026 |
| Dermaglo Colour Ltd | Manufacturing | 2024 |
| Dermaglo Tattoo Supplies Ltd | Manufacturing | 2023 |
| Dermaglo UK Limited | Manufacturing | 2002 |
| DHD Kurdish Ltd | Other services | 2023 |
| Dhikshika UK Limited | Wholesale & retail | 2021 |
| Diamond Private Hire Limited | Other services | 1993 |
| Diggin IT Landscapes & Brickwork Ltd | Construction | 2025 |
| Dinotots Childcare Limited | Health & social care | 2019 |
| Dinotots Childrens Nursery Ltd | Health & social care | 2023 |
| Dinotots Day Nursery Limited | Health & social care | 2022 |
| Dinotots Daycare Limited | Health & social care | 2021 |
| Dinsdale Property Ltd | Real estate | 2018 |
| Dinsdale Referrals Ltd | Health & social care | 2018 |
| Direct CNC Limited | Manufacturing | 2012 |
| Direct Connection 4 Limited | Information & communication | 2009 |
| Ditchburn Property Services Ltd | Construction | 2025 |
| DLG Solutions Ltd | Professional & scientific | 2017 |
| DLN High Pressure Cleaning Services Ltd | Administrative & support | 2020 |
| DM Restaurants NE Ltd | Hospitality | 2025 |
| DMC Plumbing & Heating Ltd | Construction | 2022 |
| DMC Residential Ltd | Real estate | 2021 |
| Dmrs Properties Ltd | Construction | 2026 |
| DNO Renewables Ltd | Professional & scientific | 2024 |
| Dodds Consultancy Ltd | Professional & scientific | 2024 |
| Dodds Roofing & Property Services Ltd | Construction | 2025 |
| DP Commis. Ltd | Professional & scientific | 2022 |
| Drainrat Ltd | Professional & scientific | 2025 |
| DRE Design & Build Ltd | Real estate | 2022 |
| DRE Property Group Limited | Water & waste | 2019 |
| Drivennet Ltd | Other services | 2024 |