| Darlington Motor Factors Limited | Wholesale & retail | 2005 |
| Darlington Motors Limited | Wholesale & retail | 2024 |
| Darlington Mowden Park Rugby Football Club Limited | Arts & recreation | 2005 |
| Darlington Parent Carer Forum Community Interest Company | Education | 2022 |
| Darlington Pharma Limited | Wholesale & retail | 2025 |
| Darlington Property Investments Ltd | Real estate | 2025 |
| Darlington PUB Company Ltd | Hospitality | 2025 |
| Darlington PUB Group Ltd | Hospitality | 2024 |
| Darlington Railway Enterprises Limited | Transport & logistics | 1988 |
| Darlington Railway Preservation Society | Manufacturing | 2023 |
| Darlington Residential Limited | Real estate | 2000 |
| Darlington Retired Greyhounds CIC | Administrative & support | 2023 |
| Darlington Security Limited | Professional & scientific | 2018 |
| Darlington Self Storage Ltd | Transport & logistics | 2015 |
| Darlington Skip Hire Ltd | Water & waste | 2019 |
| Darlington Solar Ltd | Construction | 2024 |
| Darlington Timber Supplies Holdings Limited | Financial services | 2025 |
| Darlington VET Clinic Limited | Professional & scientific | 2013 |
| Darlington Wind Ltd | Professional & scientific | 2025 |
| Darlington Window Cleaners Ltd | Administrative & support | 2024 |
| Darlix Trading Ltd | Wholesale & retail | 2025 |
| Darlo Barber Limited | Other services | 2023 |
| Darlo Car Repair Ltd | Wholesale & retail | 2023 |
| Darlo F & C Limited | Hospitality | 2025 |
| Darlo Fast Food Ltd | Hospitality | 2025 |
| Darlo Fish Inn Ltd | Hospitality | 2024 |
| Darlo Oven Clean Ltd | Administrative & support | 2024 |
| Darlo Subs Limited | Hospitality | 2009 |
| Darloct Limited | Hospitality | 2024 |
| Darlotl Limited | Hospitality | 2024 |
| Darnton Estates Ltd | Real estate | 2025 |
| Darnton Homes Ltd | Real estate | 2025 |
| Darou Khadim Limited | Professional & scientific | 2019 |
| Darren Grahams Building Ltd | Construction | 2025 |
| Darshan Int'L Ltd | Extraterritorial | 2014 |
| Darwell Limited | Construction | 2016 |
| Dash Electrical Ltd | Construction | 2024 |
| Dash Media Productions Ltd | Information & communication | 2022 |
| Dash Media Support Limited | Professional & scientific | 2025 |
| Datwax UK Limited | Wholesale & retail | 2021 |
| Dave Oxley Glazing Services Limited | Construction | 1991 |
| Dave Turnbull Tyres Ltd | Wholesale & retail | 2011 |
| Dave's Electrical Services Ltd | Construction | 2020 |
| Davi Peterborough Limited | Hospitality | 2019 |
| David Chadwick Design Services Limited | Administrative & support | 2009 |
| David Clark Financial Solutions Limited | Financial services | 2016 |
| David Coates Agronomy Limited | Financial services | 2009 |
| David Ford Aviation Limited | Transport & logistics | 2024 |
| David Hart Offshore Services Limited | Professional & scientific | 2017 |
| David of Durham Limited | Wholesale & retail | 2019 |
| David Ryan Plumbing and Merrybent Bathrooms Limited | Construction | 2014 |
| David Thornton Landscaping & Property Maintenance Ltd | Construction | 2024 |
| David's Dance Scores Limited | Information & communication | 2015 |
| Davies Kikai Group Ltd | Wholesale & retail | 2023 |
| Davies Transport Limited | Transport & logistics | 1995 |
| Davis Cable Solutions Limited | Construction | 2023 |
| Davison Smith Financial Management Limited | Professional & scientific | 2013 |
| Davtruk Logistics Ltd | Transport & logistics | 2025 |
| Dawnhigh Limited | | 1987 |
| DAX Winchester Engineering Ltd | Manufacturing | 2023 |
| Dayzoe Ltd | Administrative & support | 2024 |
| DB Estates Limited | Real estate | 2015 |
| Dccrs Limited | Transport & logistics | 2025 |
| DCM Project Services Ltd | Wholesale & retail | 2015 |
| Dcpo Properties Ltd | Real estate | 2026 |
| Dcs&D Limited | Health & social care | 2002 |
| Ddea Limited | Real estate | 2014 |
| DDR622 Ltd | Arts & recreation | 2025 |
| DE Garis Education Consulting Limited | Education | 2022 |
| De-Sky Multimedia UK Ltd | Arts & recreation | 2025 |
| Dealfusion Tech Labs Ltd | Information & communication | 2025 |
| Debbi Moore Designs Limited | Wholesale & retail | 2003 |
| Debbyrose Healthcare Services Ltd | Health & social care | 2025 |
| DEC Groundworks Ltd | Construction | 2012 |
| Decent Music PR Limited | Wholesale & retail | 2020 |
| Decorator DAN Limited | Administrative & support | 2025 |
| Deep Property Ltd | Real estate | 2018 |
| Deep Sea Fish Bar Ltd | Hospitality | 2019 |
| Deepdale Cove Limited | Hospitality | 2016 |
| Deerness Properties Ltd | Real estate | 2025 |
| Del's MAN & Van Ltd | Transport & logistics | 2026 |
| Delightful Carpets and Flooring Limited | Wholesale & retail | 2017 |
| Deltatwo Holdings Limited | Financial services | 2022 |
| Deltatwo Properties Limited | Real estate | 2024 |
| Deltatwo Services Limited | Professional & scientific | 2022 |
| Deluxe Reworks Ltd | Construction | 2023 |
| Demco (North East) Ltd | Transport & logistics | 2007 |
| Demi Nicole Aesthetics Ltd | Other services | 2025 |
| Demonic Spirits Limited | Manufacturing | 2022 |
| Denehead Limited | Professional & scientific | 2023 |
| Denes Local Ltd | Wholesale & retail | 2024 |
| Denham & Burd Wealth Management Limited | Financial services | 2020 |
| Denham Properties (Lettings & Property Management) Ltd | Real estate | 2022 |
| Denham Properties (NE) Limited | Real estate | 2015 |
| Denmark Street Property LLP | | 2024 |
| Denos Return Pizza N Ltd | Hospitality | 2023 |
| Dents & Dings Ltd | Wholesale & retail | 2021 |
| Depecov Ltd | Wholesale & retail | 2025 |
| Derneholme Property Holdings Ltd | Real estate | 2022 |
| DES Voeux Plan Investments (UK) Limited | Real estate | 2022 |