| Computer Clinic (Washington) Limited | Other services | 2022 |
| Concord Discount Wine Centre Ltd | Wholesale & retail | 2004 |
| Concord District Youth CIC | Arts & recreation | 2026 |
| Concord PUB Company Ltd | Hospitality | 2014 |
| Concord Shawarma Ltd | Hospitality | 2025 |
| Concord Tandoori Restaurant Limited | Hospitality | 2003 |
| Confectionery Vault Limited | Wholesale & retail | 2025 |
| Conlo Ltd | Real estate | 2018 |
| Contour Room Ltd | Other services | 2025 |
| Contract Piling Services Ltd | Construction | 2015 |
| Cook & Roebuck Limited | Professional & scientific | 2021 |
| Cooper Vance Consulting Ltd | Professional & scientific | 2023 |
| Copeland Residential Limited | Real estate | 2012 |
| Copeland Residential Sales Limited | Other services | 2013 |
| Copperplate Properties Ltd | Real estate | 2022 |
| Cortex Marketing Company Limited | Administrative & support | 2023 |
| Cosgrove Costing Limited | Professional & scientific | 2017 |
| Coulson Lift Solutions Ltd | Other services | 2022 |
| Coulson Logistics Ltd | Transport & logistics | 2022 |
| County Developments Limited | Real estate | 1991 |
| Covington & Burling LLP | | 2025 |
| Crafting Connections CIC | Education | 2021 |
| Craggs Transport Ltd | Transport & logistics | 2015 |
| Craig Falcus Limited | Professional & scientific | 2023 |
| Crampsey Pcjpl Limited | Financial services | 2025 |
| Crawfords Maintenance and Access Ltd | Construction | 2019 |
| Crime Viral Ltd | Arts & recreation | 2024 |
| Crown Doors and Shutters Limited | Manufacturing | 2007 |
| Crowther Engineering Limited | Administrative & support | 1996 |
| Crowther Garage Services Ltd | Wholesale & retail | 2019 |
| CS Project Services Limited | Professional & scientific | 2020 |
| CTA Solutions Group Ltd | Information & communication | 2025 |
| CTLC25 Limited | Real estate | 2025 |
| Ctrl Culture Ltd | Wholesale & retail | 2026 |
| Cumuluscommerce Limited | Wholesale & retail | 2025 |
| Custom Coated Kitchens Limited | Professional & scientific | 2021 |
| Cutty Sark Property Limited | Real estate | 2026 |
| CVN Commercial Limited | Professional & scientific | 2016 |
| CVS (NE) Limited | Construction | 2026 |
| CWA Ltd | Transport & logistics | 2026 |
| CX Marketing Ltd | Professional & scientific | 2022 |
| CY Accounting Solutions Ltd | Professional & scientific | 2024 |
| Cyotek Ltd | Information & communication | 2014 |
| D & B Property Management Company Limited | Real estate | 2007 |
| D & G Upholstery Limited | Manufacturing | 2006 |
| D G Joinery North East Limited | Construction | 2020 |
| D R Hydraulics & Engineering Limited | Manufacturing | 2005 |
| D R Smyth (Properties) Limited | Financial services | 2018 |
| D Squared Precision Engineering Ltd | Manufacturing | 2026 |
| D6 DEN CIC | Wholesale & retail | 2025 |
| Daccs Training Academy Limited | Other services | 2010 |
| Dagallen NDT Ltd | Professional & scientific | 2020 |
| Dajoro Limited | Other services | 2015 |
| Dalebeck Ltd | Professional & scientific | 2008 |
| Daniel Smyth Investments Limited | Financial services | 2018 |
| Dank Dollz Ltd | Information & communication | 2020 |
| Danny Ryan Electrical Ltd | Construction | 2017 |
| Dark Side Marine Ltd | Administrative & support | 2016 |
| Darkcrown Limited | Administrative & support | 2001 |
| Darmistic Ltd | Other services | 2022 |
| DAT Engineering Services Limited | Information & communication | 2008 |
| David Haley Limited | Real estate | 2010 |
| David Kilty Logistics Limited | Transport & logistics | 2018 |
| David Macleod Wind Limited | Construction | 2026 |
| Dawn Scott Elite Performance Consulting Ltd | Professional & scientific | 2025 |
| DBC Property Investments Limited | Real estate | 2024 |
| DCL Electromotive Limited | Wholesale & retail | 2022 |
| DCW Properties (NE) Limited | Real estate | 2025 |
| Debere Limited | Professional & scientific | 2015 |
| Deborah Mitchell Independent Funeral Services Ltd | Other services | 2023 |
| Decade Design Ltd | Professional & scientific | 2014 |
| Decor Flooring Limited | Construction | 2022 |
| Deemo Ltd | Information & communication | 2016 |
| Deep Blue Fish and Chips Ltd | Hospitality | 2023 |
| Dee’S Food & Clean Services Ltd | Hospitality | 2026 |
| Delishcrispys Ltd | Hospitality | 2025 |
| Deluen Holdings Ltd | Professional & scientific | 2025 |
| Denton Automation Limited | Manufacturing | 2003 |
| Deronde Ltd | Professional & scientific | 2012 |
| Design 39 - 3D Ltd | Professional & scientific | 2017 |
| Design Dynamics Ltd | Professional & scientific | 2020 |
| Design's That Work for YOU Ltd | Construction | 2025 |
| Devcycle Limited | Information & communication | 2015 |
| Dezine Properties Limited | Real estate | 2014 |
| Dfyrs Limited | Wholesale & retail | 2022 |
| DG GAS & Plumbing Ltd | Construction | 2024 |
| DGR IT Services Ltd | Information & communication | 2019 |
| DH Electrotechnical Limited | Construction | 2025 |
| Dial Electronics Limited | Wholesale & retail | 1987 |
| Diamond Consulting North East LLP | | 2010 |
| Dietitian.Pro Limited | Health & social care | 2017 |
| Digital Vintage Limited | Manufacturing | 2015 |
| Dilston Financial Services Limited | Financial services | 2011 |
| Direct Mailing Services Ltd | Other services | 2022 |
| Directsort Logistics UK Ltd | Transport & logistics | 2026 |
| Discount Vehicle Lettering Company Ltd | Manufacturing | 2008 |
| Distributions FC Limited | Wholesale & retail | 2025 |
| Divan Khanah Delivery Service Ltd | Hospitality | 2015 |
| Divanos Pizza Washington Ltd | Hospitality | 2019 |
| Divine Properties NE Ltd | Real estate | 2022 |