| DT BUS Limited | Extraterritorial | 2015 |
| DT Investments (North East) Limited | Real estate | 2024 |
| DTG Management Ltd | Professional & scientific | 2026 |
| DTL Infrastructure Group Ltd | Professional & scientific | 2025 |
| Dtrhair Durham Ltd | Other services | 2025 |
| DTY Bolting Ltd | Construction | 2019 |
| DU Clean Limited | Administrative & support | 2023 |
| DU Move Limited | Transport & logistics | 2020 |
| DUB 66 Limited | Wholesale & retail | 2019 |
| Duckworth Engineering and Construction Services Ltd | Other services | 2025 |
| Duke Estates Ltd | Real estate | 2026 |
| Dundar Global Ltd | Wholesale & retail | 2025 |
| Dunelm Construction Limited | Construction | 2022 |
| Dunelm Contracts Limited | Construction | 2025 |
| Dunelm Developments Limited | Real estate | 2024 |
| Dunelm Document Solutions Limited | Information & communication | 2009 |
| Dunelm Education Consultancy Limited | Professional & scientific | 2019 |
| Dunelm Geotechnical & Environmental Limited | Construction | 2004 |
| Dunelm Homes (Seaham) Limited | Construction | 2009 |
| Dunelm Investments Limited | Real estate | 1985 |
| Dunelm Memsis Limited | Real estate | 2022 |
| Dunelm National Projects Limited | Construction | 2010 |
| Dunelm Philatelics Ltd | Wholesale & retail | 2013 |
| Dunelm Properties Ltd | Real estate | 2025 |
| Dunelm Rentals Limited | Real estate | 2019 |
| Dunelmia Leisure Ltd | Arts & recreation | 2016 |
| Dunks Holdings Ltd | Wholesale & retail | 2025 |
| Dunn Builders Limited | Construction | 2016 |
| Dunningham (N.E.) Ltd | Professional & scientific | 2018 |
| Duoanalytical Limited | Professional & scientific | 2023 |
| Duogas Services Limited | Manufacturing | 2024 |
| Durcon Civils Ltd | Construction | 2026 |
| Durham Action on Single Housing Limited | Other services | 1972 |
| Durham Activewear Limited | Wholesale & retail | 2012 |
| Durham Alloy Refurbishment & Customisation Limited | Wholesale & retail | 2012 |
| Durham Amateur Rowing Club 1860 Limited | Arts & recreation | 2020 |
| Durham Amateur Rowing Club Limited | Hospitality | 2014 |
| Durham Aviation Ltd | Transport & logistics | 2010 |
| Durham Barber Shop Ltd | Other services | 2024 |
| Durham Bathrooms & Tiling Ltd | Construction | 2025 |
| Durham BED Centre Limited | Manufacturing | 2017 |
| Durham Business Group (NE) Ltd | Administrative & support | 1983 |
| Durham Cars Ltd | Transport & logistics | 2025 |
| Durham Catering Limited | Hospitality | 2021 |
| Durham Cathedral Open Treasure Limited | Arts & recreation | 2012 |
| Durham Cathedral Schools Foundation | Education | 1993 |
| Durham Cathedral Trading Limited | Wholesale & retail | 2007 |
| Durham China and Silver Ltd | Wholesale & retail | 2025 |
| Durham Chinese 888 Limited | Hospitality | 2025 |
| Durham City Basketball Club CIC | Education | 2026 |
| Durham City Building Services Ltd | Construction | 2018 |
| Durham City Coaches Limited | Extraterritorial | 2025 |
| Durham City GC Trading Limited | Arts & recreation | 2018 |
| Durham City Golf Club Limited | Arts & recreation | 1927 |
| Durham City Gymnastics Club C.I.C. | Arts & recreation | 2016 |
| Durham City Holdings Limited | Financial services | 2026 |
| Durham City Joinery Ltd | Construction | 2015 |
| Durham City Physio Ltd | Health & social care | 2008 |
| Durham City Property (Holdings) Limited | Real estate | 2016 |
| Durham City Property Services Ltd | Construction | 2013 |
| Durham City PUB Company Limited | Hospitality | 2019 |
| Durham City Rugby Football Club Limited | Arts & recreation | 2010 |
| Durham City Rugby Supporters Club Limited | Arts & recreation | 2016 |
| Durham City Smartzone Limited | Transport & logistics | 2018 |
| Durham City Therapy Ltd | Health & social care | 2017 |
| Durham City Transport Limited | Transport & logistics | 1991 |
| Durham Coachworks Ltd | Wholesale & retail | 2024 |
| Durham Coins Ltd | Wholesale & retail | 2024 |
| Durham Community Church | Other services | 2012 |
| Durham Community Initiatives Ltd | Construction | 2024 |
| Durham Community Kitchen C.I.C. | Hospitality | 2025 |
| Durham Complete Decking Ltd | Construction | 2010 |
| Durham Damp Proofing Ltd. | Construction | 2022 |
| Durham Decorative Supplies Limited | Wholesale & retail | 1986 |
| Durham Design and Management Limited | Construction | 2012 |
| Durham Diagnostics Limited | Information & communication | 2008 |
| Durham Dine & Wine Ltd | Hospitality | 2025 |
| Durham Diocesan Board of Finance | Other services | 1923 |
| Durham Direct Cremations Ltd | Other services | 2024 |
| Durham Dramatic Society Limited | Arts & recreation | 1946 |
| Durham Dream Homes Ltd | Real estate | 2026 |
| Durham Engineering Services Limited | Professional & scientific | 2026 |
| Durham Executive Ltd | Transport & logistics | 2026 |
| Durham Falconry Ltd | Education | 2021 |
| Durham Fencing and Landscaping Limited | Administrative & support | 2021 |
| Durham Finance Ltd | Financial services | 2025 |
| Durham Financial Services Limited | Financial services | 2013 |
| Durham Fire Protection Limited | Construction | 1998 |
| Durham FIX Group Limited | Construction | 2025 |
| Durham Flooring Limited | Wholesale & retail | 2013 |
| Durham Foods Limited | Manufacturing | 2003 |
| Durham Fringe CIC | Arts & recreation | 2021 |
| Durham Genome Centre Ltd | Professional & scientific | 2014 |
| Durham Geo-Technologies Limited | Manufacturing | 2017 |
| Durham Group Estates Limited | Real estate | 2003 |
| Durham Grove Limited | Construction | 2019 |
| Durham Halal Super Store Ltd | Wholesale & retail | 2024 |
| Durham Hand Carwash & Valeting Centre Ltd | Administrative & support | 2021 |
| Durham Hand Clinic Limited | Health & social care | 2012 |
| Durham Health Food Ltd | Hospitality | 2016 |