| D6 Culture Ltd | Arts & recreation | 1991 |
| DA Architecture Limited | Professional & scientific | 2017 |
| DA Knowles Limited | Administrative & support | 2025 |
| DA Peshawar DE Ltd | Hospitality | 2025 |
| DA Vince Pizza Ltd | Hospitality | 2022 |
| Da'Lemmaa Network Ltd | Arts & recreation | 2026 |
| Daauk Ltd | Information & communication | 2023 |
| Daava Developments (UK) Limited | Construction | 2012 |
| DAB Medical Reporting Ltd | Health & social care | 2018 |
| DAB Reporting Limited | Information & communication | 2022 |
| Dabba Social Limited | Hospitality | 2024 |
| Dabeer Limited | Wholesale & retail | 2025 |
| Dabrosh Solutions Limited | Real estate | 2024 |
| DAC (NE) Ltd | Real estate | 2022 |
| DAC Distribution Limited | Transport & logistics | 2018 |
| Dacre Court Management Limited | Households | 1984 |
| Daddy James Ltd | Professional & scientific | 2026 |
| Dadr Ltd | Real estate | 2023 |
| Daek Daun Ltd | Hospitality | 2019 |
| Daemma Trading Group Limited | Financial services | 2024 |
| Daemma Trading Holdings Limited | Financial services | 2024 |
| Daft AS a Brush Cancer Patient Care Charitable Trust | Other services | 1989 |
| Dahlia Limited | Real estate | 2024 |
| Dahlia Property Limited | Real estate | 2025 |
| Daily Manna Ltd | Hospitality | 2025 |
| Daily News Delivered Ltd | Information & communication | 2020 |
| Daisy Croft Cottage Limited | Hospitality | 2020 |
| Daisymaid Commercial Limited | Administrative & support | 2014 |
| Daisymaid NE Limited | Administrative & support | 2013 |
| Daktal Ltd | Hospitality | 2011 |
| Dalby Properties Limited | Real estate | 2021 |
| Dalehead Developments Limited | Wholesale & retail | 1981 |
| Dalemaine Properties Ltd | Real estate | 2023 |
| Daley Express Limited | Transport & logistics | 2005 |
| Daley Lettings Limited | Real estate | 2015 |
| Dalluyon Studio Ltd | Wholesale & retail | 2026 |
| Dalstone Roseberry Ltd | Hospitality | 2026 |
| Dame Allan's Schools | Education | 2000 |
| Dame Margaret Hall (East Wing) RTM Company Limited | Real estate | 2015 |
| Dame Margaret Hall RTM Company Limited | Real estate | 2015 |
| Damf (NE) Ltd | Real estate | 2017 |
| Damian Cronin Holdings Limited | Financial services | 2023 |
| Dampfix NE Ltd | Construction | 2025 |
| Dams Renewables Limited | Construction | 2020 |
| DAN and Nick Food Limited | Hospitality | 2024 |
| DAN Aziz Ltd | Professional & scientific | 2011 |
| DAN Holdsworth Studio Limited | Arts & recreation | 2011 |
| Dana North East Properties Ltd | Real estate | 2019 |
| Danalogue Ltd | Professional & scientific | 2023 |
| Dance Artists North East CIC | Administrative & support | 2024 |
| Dance Fusion Extreme CIC | Arts & recreation | 2018 |
| Dance Revolution Media Ltd | Information & communication | 2021 |
| Danceheaven Ltd | Wholesale & retail | 2020 |
| Danceplex Ltd | Arts & recreation | 2021 |
| Dandelion Confidence CIC | Education | 2023 |
| Dane & Co., Limited | Financial services | 2013 |
| Dane Architectural Systems Holdings EOT Limited | Administrative & support | 2019 |
| Dane Architectural Systems Holdings Limited | Construction | 2013 |
| Dane Architectural Systems Limited | Construction | 1971 |
| Dane Finance Limited | Financial services | 2013 |
| Dane Group Holdings Limited | Professional & scientific | 2013 |
| Dane Property Limited | Real estate | 2013 |
| Daneen&Co Ltd | Wholesale & retail | 2022 |
| Danesfield Legal Services Limited | Administrative & support | 2014 |
| Daneshi Property Development Ltd | Households | 2020 |
| Dangerous Technologies Ltd | Information & communication | 2023 |
| Dani Davies Limited | Arts & recreation | 2025 |
| Danicy Consulting Ltd | Information & communication | 2020 |
| Daniel Dixon Process Engineering Ltd | Professional & scientific | 2020 |
| Daniel Gallon Optical Ltd | Wholesale & retail | 2025 |
| Daniel's Barbers Ltd | Other services | 2026 |
| Daniela Limited | Hospitality | 2000 |
| Daniela Sparks Ltd | Transport & logistics | 2023 |
| Danielchristianmaill Limited | Construction | 2014 |
| Danieli Group Limited | Financial services | 2022 |
| Danieli Holdings Limited | Professional & scientific | 2008 |
| Danika ESS Copywriting Ltd | Professional & scientific | 2020 |
| Danish Ecom Ltd | Wholesale & retail | 2025 |
| Danni's Nails & Beauty Limited | Other services | 2020 |
| Danshan Ltd | Real estate | 2017 |
| Danu Studios Ltd | Other services | 2021 |
| Danvy Estates Limited | Real estate | 2022 |
| Daodi Ltd | Real estate | 2025 |
| Dappleblack Communications Limited | Administrative & support | 2014 |
| Dara Networks Ltd | Administrative & support | 2012 |
| Dara Travel Ltd | Administrative & support | 2025 |
| Darcy & Co (NE) Ltd | Construction | 2023 |
| Dardania Developments Ltd | Construction | 2025 |
| Dare Technology Limited | Information & communication | 2020 |
| Dare Technology Trustee Limited | Administrative & support | 2025 |
| Dargaval Investments Ltd | Mining & quarrying | 2025 |
| Darius Express Limited | Wholesale & retail | 2026 |
| Dark AS RUM Construction Ltd | Construction | 2016 |
| Dark Fuchsia Ltd | Financial services | 2023 |
| Darkness Media Ltd | Manufacturing | 2025 |
| Darkus Ltd | Information & communication | 2025 |
| Darlington & District Motor Club Limited | Arts & recreation | 1956 |
| Darlington Chelsea Court Limited | Real estate | 2002 |
| Darlington Dorchester Court Limited | Real estate | 2002 |
| Darnell Trade Prices Limited | Wholesale & retail | 2012 |