| Colton Contractors Ltd | Transport & logistics | 2024 |
| Compass 24 Hour Breakdown Recovery Ltd | Transport & logistics | 2021 |
| Construct Group Design & Build Ltd | Construction | 2025 |
| Construct North East Ltd | Construction | 2023 |
| Construction Plant Hire NE Ltd | Administrative & support | 2026 |
| Construction Plant Sales Ltd | Wholesale & retail | 2026 |
| Construction Trades Supply Ltd | Wholesale & retail | 2026 |
| Cook&Pearson Joinery Services Ltd | Construction | 2015 |
| Cornforth Fisheries Limited | Hospitality | 2026 |
| Cortex Collective Limited | Professional & scientific | 2025 |
| Costa Enterprises Holdings Limited | Professional & scientific | 2011 |
| Costaeh Retail Ltd | Administrative & support | 2016 |
| Cotilda Limited | Manufacturing | 2015 |
| County Durham Furniture Help Scheme | Water & waste | 2005 |
| Crbthl Trading Ltd | Wholesale & retail | 2025 |
| CRU Construction (Services) Ltd | Construction | 2013 |
| CT Commercial Finance Ltd | Financial services | 2014 |
| Cumbria Animal and HEN Rescue CIC | Administrative & support | 2018 |
| D Plant Plumbing & Heating Ltd | Construction | 2025 |
| D&J Plumbing and Heating(Durham) Ltd | Construction | 2020 |
| D. Farnaby Limited | Transport & logistics | 2008 |
| Darlington Islamic Academy Ltd | Education | 2020 |
| Deltaflash Energy Limited | Professional & scientific | 2017 |
| Design PIG Ltd | Professional & scientific | 2012 |
| DH8 Ltd | Financial services | 2025 |
| Dickson Offshore Ltd | Transport & logistics | 2019 |
| Dimension Breakers Ltd | Transport & logistics | 2017 |
| Direct Professional Suppliers Limited | Manufacturing | 1994 |
| DIY Roofing Solutions Ltd | Construction | 2025 |
| DJ Bell Offshore Ltd | Professional & scientific | 2025 |
| Django Sales UK Ltd | Wholesale & retail | 2023 |
| Dm's Aesthetics Limited | Other services | 2023 |
| Dmhm Limited | Wholesale & retail | 2015 |
| Doctor Bake Limited | Real estate | 2015 |
| Doddsdelivers Ltd | Transport & logistics | 2025 |
| Dolphin Blue Ltd | Financial services | 2016 |
| Dolphin Leisure Limited | Other services | 2013 |
| Dougherty LET & Living Co Ltd | Real estate | 2026 |
| DPE Alpha Properties Limited | Real estate | 2021 |
| Dragonfly Window Cleaning Ltd | Administrative & support | 2025 |
| Dripforce Limited | Wholesale & retail | 2025 |
| Duff Holdings Limited | Financial services | 2023 |
| Durham Animal Feeds East Ltd | Manufacturing | 2022 |
| Durham Animal Feeds Limited | Manufacturing | 2015 |
| Durham Animal Feeds North Ltd | Manufacturing | 2022 |
| Durham Animal Feeds South Limited | Manufacturing | 2015 |
| Durham Bikes Limited | Wholesale & retail | 2018 |
| Durham Slates Limited | Professional & scientific | 2025 |
| DW Commercials [NE] Ltd | Wholesale & retail | 2024 |
| Dynamic Aerospace and Defense Limited | Financial services | 2016 |
| Eden Development Services Ltd | Professional & scientific | 2023 |
| Eden Learning Trust | Education | 2017 |
| Electric Services Direct Limited | Extraterritorial | 2025 |
| Elite Consult Group Ltd | Administrative & support | 2020 |
| Elite Property Management & Investment Group Ltd | Real estate | 2026 |
| Elmtone Properties Limited | Construction | 1994 |
| Elvet Grey Property Group Ltd | Real estate | 2026 |
| EMT Medical Ltd | Administrative & support | 2017 |
| Encompass Integrated Solutions Limited | Information & communication | 2014 |
| Endeavour Woodcraft Community Interest Company | Manufacturing | 1992 |
| Envisage Training Limited | Professional & scientific | 2013 |
| Eppleton Quarry Products Limited | Mining & quarrying | 2001 |
| EPS Electrical Services Ltd | Construction | 2019 |
| Escape Music Ltd. | Other services | 1996 |
| ESD1 Limited | Extraterritorial | 2025 |
| Exaudi | Education | 2010 |
| Exigent Quality Assurance Ltd | Information & communication | 2023 |
| Express Motor Factors Limited | Wholesale & retail | 2011 |
| F&P Property Development Ltd | Real estate | 2026 |
| Falcon Propagation Ltd | Agriculture & fishing | 2015 |
| Fc's O&G Services Ltd | Administrative & support | 2025 |
| FD Trading Ltd | Construction | 2023 |
| Ferrydec Limited | Real estate | 1974 |
| Ferryhill Caravan & Motorhome Storage Ltd | Administrative & support | 2024 |
| Ferryhill Lakes and District Development Education Resource Centre Limited | Administrative & support | 2000 |
| Ferryhill Lettings Limited | Real estate | 2009 |
| Ferryhill Mini Market Ltd | Wholesale & retail | 2025 |
| Ferryhill Nails & Spa 1 Ltd | Other services | 2025 |
| Ferryhill Nails & Spa 8 Ltd | Other services | 2026 |
| Ferryhill Village Travel Limited | Transport & logistics | 2024 |
| Finchale Woodland Ltd | Hospitality | 2014 |
| Finnshea Investments Ltd | Professional & scientific | 2024 |
| Fired UP (NE) Ltd | Construction | 2020 |
| First Choice Cleaning Services Ltd | Administrative & support | 2025 |
| Fishburn Airfield Limited | Transport & logistics | 2003 |
| Fit Brands Fulfillment Ltd | Wholesale & retail | 2023 |
| Flawless Finish Facilities Ltd | Administrative & support | 2025 |
| Fleurise Ltd. | Information & communication | 2011 |
| Fluffiesnfriends Ltd | Wholesale & retail | 2023 |
| Fmh.Catering Ltd | Hospitality | 2017 |
| Fort Cleaning Services Ltd | Administrative & support | 2025 |
| Foster Transport Developments Ltd | Real estate | 2014 |
| FOZ Collectibles Limited | Wholesale & retail | 2026 |
| Frensic & Frensic Limited | Professional & scientific | 2002 |
| G M B Protection Ltd | Wholesale & retail | 2018 |
| G & L Brown Property Development Ltd | Real estate | 2022 |
| G Bolam Foods (Holdings) Limited | Real estate | 2025 |
| G M B Tech Online Ltd | Wholesale & retail | 2019 |
| G.T. Commercials (NE) Ltd | Wholesale & retail | 2023 |
| Galea Services Ltd | Professional & scientific | 2016 |