| Blue Star Express Logistics Limited | Transport & logistics | 2010 |
| BMR Bricklaying Services Ltd | Construction | 2023 |
| BMS Consultants Ltd | Professional & scientific | 2018 |
| BNH (North East) Limited | Administrative & support | 2018 |
| Bodacii Ltd | Wholesale & retail | 2022 |
| Bolbec Manor Ltd | Hospitality | 2021 |
| Bowditch Property Solutions Ltd | Real estate | 2024 |
| Boyle Worldwide Ltd | Information & communication | 2017 |
| Briar MEW Holdings Limited | Professional & scientific | 2023 |
| Briardale Local Ltd | Wholesale & retail | 2021 |
| Briarmead Architecture Ltd | Professional & scientific | 2026 |
| Bridge END Lodges Ltd | Hospitality | 2016 |
| Bridge Island Management Company Limited | Real estate | 2003 |
| Bridget & BEA Ltd | Agriculture & fishing | 2021 |
| Broad Clothing Ltd | Wholesale & retail | 2025 |
| Brookfield Motor Company Limited | Wholesale & retail | 2021 |
| BRS Residential Ltd | Real estate | 2025 |
| Brush Wizards Ltd | Construction | 2023 |
| Bryansburn Ltd | Real estate | 2025 |
| BSW Group Limited | Construction | 2021 |
| Build-Form Construction Ltd | Construction | 2021 |
| Building Interior Supplies Limited | Wholesale & retail | 2017 |
| Bullying Intervention Limited | Education | 2011 |
| Bunbun and BMO Limited | Information & communication | 2024 |
| Burnco Limited | Real estate | 2013 |
| Burns DCS Ltd | Professional & scientific | 2023 |
| Business Cost Comparison Ltd | Professional & scientific | 2018 |
| Butler & GEE Accountants Ltd | Professional & scientific | 2007 |
| Buzzin' Records Ltd | Arts & recreation | 2020 |
| BW Haulage Limited | Transport & logistics | 2010 |
| C H Morrison Ltd | Health & social care | 2003 |
| C M Holdings (North East) Limited | Financial services | 2026 |
| C O'Neill Consultancy Ltd | Professional & scientific | 2021 |
| C&L Utilities (North East) Limited | Construction | 2022 |
| C-T-S Towbar’S Ltd | Professional & scientific | 2024 |
| Cabe Timber Frame Ltd | Construction | 2020 |
| Cafe at Inn on the Park Limited | Hospitality | 2018 |
| Cakebox Middlesbrough Ltd | Administrative & support | 2018 |
| Calico Studios NE Ltd | Other services | 2024 |
| Calltronics Limited | Manufacturing | 2004 |
| Campaigns LAB Limited | Professional & scientific | 2024 |
| Campbelltown Care PVT Ltd | Health & social care | 2023 |
| Canny Gluten Free Pizza Ltd | Wholesale & retail | 2026 |
| Cantharellus Ltd | Professional & scientific | 2023 |
| Cape Farming & Bloodstock Limited | Agriculture & fishing | 2020 |
| Cape Farming and Forestry Limited | Agriculture & fishing | 2021 |
| Caravan Storage Durham Ltd | Transport & logistics | 2015 |
| Carl Swinbank Joinery Limited | Construction | 2021 |
| Carlene's Places Ltd | Real estate | 2025 |
| Carol H Limited | Administrative & support | 2026 |
| Carr GEO Engineering Limited | Construction | 2014 |
| Carrhouse Property Services Ltd | Real estate | 2025 |
| Carson Property Maintenance Limited | Administrative & support | 2014 |
| Cartena Holdings Ltd | Financial services | 2026 |
| Carter Bros Properties Ltd | Real estate | 2022 |
| Carter Construction (North East) Limited | Construction | 2022 |
| Carter Consult Group Ltd | Information & communication | 2024 |
| Cartmell Solutions Ltd | Professional & scientific | 2025 |
| Carvell Associates Limited | Professional & scientific | 2012 |
| Casalingua Ltd | Education | 2024 |
| Cast Rental & Development Limited | Real estate | 2020 |
| Castleside Club Football Club Ltd | Arts & recreation | 2025 |
| Castleside Commercials Limited | Wholesale & retail | 2016 |
| Castleside Horse & Groom Ltd | Hospitality | 2018 |
| Castleside Minerals Limited | Professional & scientific | 2025 |
| Catori Beauty Ltd | Other services | 2022 |
| CAV Acquisition Limited | Financial services | 2023 |
| CAV Advanced Technologies Limited | Manufacturing | 2008 |
| CAV Ice Protection Limited | Manufacturing | 2008 |
| CAV Systems Limited | Other services | 2017 |
| Cavalier Property Group Limited | Real estate | 2025 |
| CC Geotech Ltd | Transport & logistics | 2019 |
| CCT Comms Ltd | Information & communication | 2018 |
| CD Rigging Ltd | Construction | 2024 |
| Cdelectrical Solutions Limited | Construction | 2023 |
| CEL Homecare Limited | Health & social care | 2019 |
| CEL Sheet Metal (Holdings) Limited | Financial services | 2022 |
| Celebrate Difference Ltd | Health & social care | 2021 |
| CF Energy Limited | Professional & scientific | 2015 |
| CF Telecom Solutions Ltd | Information & communication | 2021 |
| Cflattery Ltd | Health & social care | 2025 |
| Chaplains Bar and Lounge Consett Ltd | Hospitality | 2023 |
| Chaplains Consett Ltd | Hospitality | 2018 |
| Chaplains Consett PM Ltd | Hospitality | 2026 |
| Chapman Estate Homes Ltd | Real estate | 2024 |
| Chapman Estates Consett Ltd | Real estate | 2026 |
| Chapman Estates Investments Ltd | Real estate | 2024 |
| Chapman Estates Lettings & Management Ltd | Real estate | 2025 |
| Chapman Estates North East Ltd | Real estate | 2024 |
| Charlton International Holdings Limited | Administrative & support | 2020 |
| Chetna Spice Ltd | Hospitality | 2021 |
| CHH Contracts Ltd | Construction | 2023 |
| Chimney Sweep Theatre School Ltd | Education | 2018 |
| Chopping Block N E Limited | Other services | 2015 |
| Chris Daniels Consulting Limited | Professional & scientific | 2015 |
| CJ Ayton Ltd | Manufacturing | 2022 |
| CJ Bushby and Co Ltd | Education | 2023 |
| CJS Interiors North East Ltd | Construction | 2019 |
| Ckon Holdings Limited | Real estate | 2016 |
| CL Engineering Limited | Manufacturing | 2016 |