| 0537277 Limited | Manufacturing | 1954 |
| A & B Industrial Cleaning Limited | Administrative & support | 2006 |
| A & F Bell Holdings Limited | Financial services | 2022 |
| A SIX Ninety Warranties Limited | Wholesale & retail | 2010 |
| A. Charles Thomas (Care) Limited | Health & social care | 1987 |
| A.J.Siris Products Limited | | 1945 |
| A.W. Walker & Sons (Darlington) Limited | | 1980 |
| A1 Security Services (North East) Ltd | Administrative & support | 2008 |
| Adam Booth IT Services Limited | Information & communication | 2010 |
| Adventure Valley Day Nursery Limited | Education | 2018 |
| AIM High Attendance Solutions Limited | Education | 2022 |
| Alderclad Ltd | Construction | 2005 |
| Alphatec P.F.E. Limited | Wholesale & retail | 2005 |
| Armstrongs Bakers (Consett) Limited | | 1971 |
| Asem Overseas Properties Limited | Real estate | 2005 |
| Atkinsons Joiners Limited | Manufacturing | 2005 |
| Autoservice (Stanley) Ltd | Wholesale & retail | 2024 |
| AWC Insurance Services Ltd | Financial services | 2003 |
| Axenic Limited | Manufacturing | 2009 |
| Axton Computers Ltd | Manufacturing | 2009 |
| Aycliffe Physiotherapy Ltd | Other services | 2021 |
| B.H. Nelson & Co. Limited | Construction | 1978 |
| Barnard Castle and Teesdale Farmers Auction Mart Company Limited(The) | Other services | 1890 |
| Batson Groundcare Ltd | Administrative & support | 2002 |
| Billy Davidson NV Stables Limited | Manufacturing | 2005 |
| Blast Tech North East Ltd | Wholesale & retail | 2018 |
| Brambles Farm Ltd | Wholesale & retail | 2007 |
| Brancepeth Castle Golf Club,Limited(The) | Arts & recreation | 1931 |
| Broom Mill Farms Spa Limited | Arts & recreation | 2004 |
| Budge Construction Limited | Construction | 2004 |
| Byers Groundworks Limited | Construction | 2004 |
| Carlton Lending Limited | Financial services | 2019 |
| Castle Keep Geospatial Ltd | Extraterritorial | 2022 |
| Castle Keep Site Engineering Ltd | Construction | 2022 |
| Castle Keep Surveys Limited | Construction | 2016 |
| Castle Keep Utilities Ltd | Extraterritorial | 2022 |
| Cestrian Commission Agents Limited | Real estate | 1966 |
| Charlton Blair (Beadnell) Limited | Real estate | 2022 |
| Charlton Blair (Homes) Limited | Real estate | 2021 |
| Charlton Blair (Stirling Court) Limited | Real estate | 2022 |
| Chester-Le-Street Haulage Limited | Construction | 1947 |
| Claire International Limited | Manufacturing | 1986 |
| Complete Carbon Solutions Ltd | Professional & scientific | 2008 |
| Cook Developments Limited | Real estate | 2010 |
| Crown Garage Cockfield Limited | Wholesale & retail | 2003 |
| D. Ward Automotive Limited | Wholesale & retail | 2004 |
| Darlington Timber Supplies Limited | Wholesale & retail | 1986 |
| Delta C Design Limited | Construction | 2005 |
| Deltaflash Limited | Professional & scientific | 1984 |
| Derek Smith Construction (N.E.) Limited | | 1981 |
| DSB Connections Ltd | Manufacturing | 2016 |
| Dual Logic Ltd | Construction | 2007 |
| Duff & Shaw Express Engineering Limited | | 1971 |
| Dunelm Plant Services Ltd | Construction | 2018 |
| Durham Ditching and Drainage Company Limited | | 1960 |
| Durham River Cruises Limited | Transport & logistics | 2004 |
| Ecomode LED Limited | Wholesale & retail | 2020 |
| Elitegold Limited | | 1979 |
| Ensure (IFA) Limited | Financial services | 2004 |
| Exis Maintenance Services Limited | Administrative & support | 2006 |
| Expert Control Limited | Real estate | 1992 |
| Farmtastic Valley Limited | Arts & recreation | 2007 |
| Fireeagle Limited | Real estate | 1984 |
| First Class Commercials Limited | Wholesale & retail | 1991 |
| Flintnorm Limited | Real estate | 1984 |
| Flora House Day Nursery Limited | Health & social care | 2006 |
| G Brownless & SON Limited | Other services | 2006 |
| G P Stelling Limited | Construction | 2006 |
| Gainford Hotels Limited | Hospitality | 2012 |
| Gardiner Bros. Limited | Transport & logistics | 1980 |
| Gary Douthwaite Plumbing & Heating Limited | Construction | 2003 |
| Gecadis Management Limited | Other services | 2016 |
| GLH NE Ltd | Wholesale & retail | 2026 |
| Greenline Wholesale Fruit & VEG. Limited | Wholesale & retail | 2004 |
| Growth Capital Ventures Limited | Information & communication | 2012 |
| H F Colton Plant Hire Ltd | Construction | 2002 |
| H.N.Marsh & Co.Limited | | 1951 |
| Hanwest Limited | | 1978 |
| Hardwick Associates Limited | Hospitality | 1998 |
| Hatton Parcel Delivery Ltd | Transport & logistics | 2023 |
| Hayton Property Investments Limited | Construction | 2026 |
| Heritage Plumbing and Heating Services Limited | Administrative & support | 2006 |
| Heswall Engineering Limited | | 1963 |
| High Lands Farms Limited | Wholesale & retail | 2005 |
| Homecare Heating Supplies Teesside Limited | Wholesale & retail | 1974 |
| Horizon Glass Limited | Construction | 1997 |
| Ineos Compounds Aycliffe Limited | Manufacturing | 2013 |
| Ineos Compounds Holdings Limited | Manufacturing | 2013 |
| Ineos Compounds UK Ltd | Manufacturing | 1990 |
| Ineos Nitriles (UK) Limited | Manufacturing | 2007 |
| Innerspace Builders Ltd | Construction | 2019 |
| J C Brown Limited | Administrative & support | 2004 |
| J R Humble & Sons Limited | Transport & logistics | 2003 |
| J R Walker (Building) Limited | Construction | 2007 |
| J S Rusby Ltd | Construction | 2002 |
| J.S.Limited | Financial services | 1904 |
| James Dinsley & SON Limited | Construction | 2005 |
| JLG Offshore Consulting Limited | Professional & scientific | 2016 |
| JRB Commercial Limited | Professional & scientific | 2023 |
| Kanaa Property Ltd | Real estate | 2021 |