| Albion EMS Limited | Professional & scientific | 2021 |
| Alfa-Stucco Ltd | Construction | 2019 |
| Andrea Irving-Morse Associates Limited | Professional & scientific | 2016 |
| Aquariux Limited | Information & communication | 2023 |
| Ascarii Group Holdings Limited | Financial services | 2024 |
| Ascarii Limited | Information & communication | 2012 |
| Astrogate Labs UK Limited | Information & communication | 2024 |
| Bennett Builders Ltd | Construction | 2025 |
| Bolam Properties Ltd | Real estate | 2022 |
| Bradbury Leisure Ltd | Other services | 2003 |
| Buchanan IT Consultancy Ltd | Information & communication | 2010 |
| Burdessdc Ltd | Professional & scientific | 2019 |
| Containers NOW Limited | Wholesale & retail | 2015 |
| Cortirio Limited | Information & communication | 2017 |
| Darlington & Durham Professional & Community Therapies Ltd | Information & communication | 2023 |
| DC Luxury Real Estate Limited | Real estate | 2025 |
| DD IT Solutions Limited | Information & communication | 2015 |
| DDF Fairs Limited | Wholesale & retail | 2003 |
| Dewpoint Renewables Ltd | Professional & scientific | 2023 |
| Enerus Limited | Professional & scientific | 2020 |
| Excyton Limited | Professional & scientific | 2019 |
| Filter Integrity Limited | Professional & scientific | 2010 |
| Filtronic Broadband Limited | Manufacturing | 1997 |
| Filtronic Holdings UK Limited | Professional & scientific | 2006 |
| Filtronic PLC | Manufacturing | 1994 |
| Filtronic Wireless Ltd | Manufacturing | 1978 |
| First Graphene (UK) Limited | Manufacturing | 2018 |
| Fortay Consulting LLP | | 2024 |
| Foxton Wood Holdings Limited | Financial services | 2020 |
| Friends of Ropner Park Limited | Administrative & support | 2007 |
| G.B. Management Solutions Limited | Professional & scientific | 2004 |
| GH Engineering Solutions Ltd | Manufacturing | 2014 |
| GLC Consult Ltd | Professional & scientific | 2018 |
| GLC Projects Ltd | Construction | 2019 |
| Goldsmith Software Consulting Limited | Information & communication | 2020 |
| H T Process Control Ltd | Wholesale & retail | 2011 |
| Hopper House Brew Farm Ltd | Manufacturing | 2019 |
| HOSTS365 Web Services Limited | Information & communication | 2021 |
| I2B Limited | Information & communication | 2002 |
| ID Films Ltd | Other services | 2014 |
| IN2INTERESTS Limited | Education | 2014 |
| Isotek (Holdings) Limited | Professional & scientific | 1997 |
| J N I Rolling Stock Limited | Wholesale & retail | 2019 |
| John Nelson Surveying Services Ltd | Professional & scientific | 2017 |
| John R. Johnson Ltd | Construction | 2019 |
| Kitchen Calm Limited | Wholesale & retail | 2007 |
| Kromek (Germany) Limited | Wholesale & retail | 2013 |
| Kromek Group PLC | Manufacturing | 2013 |
| Kromek Limited | Manufacturing | 2003 |
| Lion Oak Advisory Limited | Information & communication | 2025 |
| LOW Hardwick Farm Ltd | Agriculture & fishing | 2023 |
| Magnitude Biosciences Limited | Professional & scientific | 2018 |
| Mobibud Limited | Information & communication | 2018 |
| Motif Digital Marketing Ltd | Professional & scientific | 2019 |
| MSD Rail (UK) Ltd | Construction | 2013 |
| MYB Business Development Limited | Administrative & support | 2024 |
| Northern Light Optical Limited | Manufacturing | 2020 |
| Northumbria Pharma Ltd | Manufacturing | 2016 |
| Notis Ltd | Information & communication | 2017 |
| Olsen Moor Limited | Wholesale & retail | 2008 |
| P&A Doors & Windows Ltd | Wholesale & retail | 2015 |
| Pallister Estates Limited | Real estate | 2019 |
| PCE Holdings Limited | Wholesale & retail | 2018 |
| Platts Physiotherapy Limited | Health & social care | 2013 |
| PNK Properties (North East) Limited | Real estate | 2022 |
| Polyphotonix Limited | Professional & scientific | 2008 |
| Polyphotonix Medical Ltd | Professional & scientific | 2011 |
| Primrose Consultants Ltd | Professional & scientific | 2024 |
| Pro Agrotech Ltd | Agriculture & fishing | 2018 |
| Proactive Leisure Limited | Administrative & support | 2003 |
| Process Control Equipment Limited | Wholesale & retail | 1980 |
| Process Control Equipment Scotland Limited | Wholesale & retail | 1997 |
| Proteus Materials Limited | Professional & scientific | 2020 |
| Quorum Development Ltd | Information & communication | 2002 |
| Right Lines Communications Limited | Professional & scientific | 2012 |
| Riverside Event Catering Limited | Hospitality | 2020 |
| RMC Bulk Logistics Ltd | Transport & logistics | 2025 |
| Satmos Limited | Wholesale & retail | 2008 |
| Savvy Science Limited | Professional & scientific | 2017 |
| Sean Finnigan Inspections Limited | Construction | 2010 |
| Sedgefield Chem Ltd | Wholesale & retail | 2023 |
| Sedgefield Fisheries Ltd | Hospitality | 2024 |
| Sedgefield Holdings Ltd | Financial services | 2023 |
| Sedgefield Pottery Supplies Limited | Wholesale & retail | 2006 |
| Semtelligence Limited | Information & communication | 2011 |
| Signature Botanics Ltd | Wholesale & retail | 2022 |
| Sinclarity Solutions Ltd | Information & communication | 2011 |
| South Durham Ltd | Hospitality | 2025 |
| Southmoor Equine Therapy Limited | Other services | 2024 |
| Southmoor Livery NO 2 Limited | Agriculture & fishing | 2024 |
| Southmoor Livery NO1 Limited | Agriculture & fishing | 2024 |
| Stonecrop Lodge Limited | Real estate | 2026 |
| Symaset Ltd | Professional & scientific | 2021 |
| TCJ Construction Services Ltd | Professional & scientific | 2011 |
| THE Healing Cauldron Ltd | Wholesale & retail | 2018 |
| THE Healing Cauldron Supplements Ltd | Wholesale & retail | 2020 |
| THE Luxe Voyager Ltd | Professional & scientific | 2023 |
| THE Solution Injury Clinic Limited | Health & social care | 2021 |
| Thisisusuk C.I.C. | Transport & logistics | 2019 |
| Trab Rentals Limited | Households | 2022 |