| Delta Energy Cables Limited | | 1996 |
| Delta Shipping Limited | | 1985 |
| Delux Bathrooms and Tiling Solutions (NI) Limited | Construction | 2023 |
| DEM Co 2 | Financial services | 2014 |
| DEM Maintenance Limited | Construction | 1978 |
| Dementia (NI) | Health & social care | 2015 |
| Demesne (Fortwilliam) Management Company Limited - the | Extraterritorial | 2005 |
| Demesne Gate Management Limited | Households | 2004 |
| Demesne Investments Limited | Administrative & support | 2006 |
| Demesne Mews (NI) Management Company Limited | Households | 2022 |
| Demo Vent Ltd | Construction | 2026 |
| Den.Co.Down Ltd | Health & social care | 2010 |
| Denberg Ltd | Professional & scientific | 2011 |
| Dencare Services Ltd | Health & social care | 2026 |
| Deng BO Ltd | Wholesale & retail | 2023 |
| Dengdai Ltd | Wholesale & retail | 2024 |
| Dengfangna Ltd | Wholesale & retail | 2024 |
| Dengqiang CAN Limited | Wholesale & retail | 2025 |
| Dengzhixin Limited | Wholesale & retail | 2024 |
| Denis Montgomery Limited | Professional & scientific | 1992 |
| Denise Mccartan Psychology Limited | Health & social care | 2015 |
| Denmin Ltd | Wholesale & retail | 2012 |
| Dennis Boyd & Co Limited | Professional & scientific | 2013 |
| Dennison Byrne Ltd | Professional & scientific | 2022 |
| Dennison Partnership Limited | Transport & logistics | 2014 |
| Denovo N I Limited | Health & social care | 2025 |
| Densave Limited | Health & social care | 2000 |
| Dental Aesthetics Ltd | Health & social care | 2008 |
| Dental Excellence Group Ltd | Health & social care | 2011 |
| Dental Excellence Ltd | Health & social care | 2008 |
| Dental World 1 Limited | Health & social care | 2016 |
| Dentology PDR Services Ltd | Wholesale & retail | 2021 |
| Denvir Holdings Limited | Professional & scientific | 2013 |
| Denvir's of Downpatrick Limited | Hospitality | 2013 |
| Deoingrid.Co Ltd | Hospitality | 2025 |
| Depanneur Ltd | Hospitality | 2025 |
| Depaul Northern Ireland | Professional & scientific | 2005 |
| Dependable Offshore Personnel Ltd | Administrative & support | 2013 |
| Depot HQ Ltd | Information & communication | 2003 |
| Deramore (Belfast) Limited | Construction | 2016 |
| Deramore Apartments Limited | Households | 1981 |
| Deramore Developments Limited | Construction | 2012 |
| Deramore Grange Company Limited-The | Households | 1991 |
| Deramore Investments Ltd | Real estate | 2013 |
| Deramore Manor Limited | Households | 1989 |
| Deramore Mews Limited | Households | 1999 |
| Deramore Properties Limited | Real estate | 2018 |
| Derek Millar Electrical Limited | Construction | 2011 |
| Derek White Mechanical Limited | Professional & scientific | 2016 |
| Derma Epsilon Ltd | Health & social care | 2025 |
| Dermar Developers Ltd | Construction | 2020 |
| Dermatome Ltd | Health & social care | 2025 |
| Dermont NO.2 LLP | | 2008 |
| Dermont NO.3 LLP | | 2008 |
| Derpathfinder Ltd | Administrative & support | 2023 |
| Derry Lane Management Limited | Households | 2007 |
| Derryadd Limited | Real estate | 2023 |
| Derryadd Seoul Limited | Wholesale & retail | 2024 |
| Derrychaan Ltd | Health & social care | 2016 |
| Derrylettiff Farms Ltd | Agriculture & fishing | 2019 |
| Derrylodge Property Management Ltd | Households | 2014 |
| Derrynanny Wind Ltd | Energy | 2021 |
| Derryvolgie Park Lane Management Company Limited | Real estate | 2024 |
| Desert Rose Trading Ltd | Wholesale & retail | 2025 |
| Design and Reason Ltd | Professional & scientific | 2018 |
| Design Electrical & Energy Services Limited | Construction | 2017 |
| Designni Ltd | Professional & scientific | 2021 |
| Designtab Ltd | Professional & scientific | 2021 |
| Desire Hair Belfast Limited | Other services | 2023 |
| Desire Light Limited | Wholesale & retail | 2024 |
| Desk Warehouse Limited - the | Wholesale & retail | 2006 |
| Despina Limited | Real estate | 2016 |
| Dessert Ville Belfast Ltd | Hospitality | 2025 |
| Dessertsni Limited | Wholesale & retail | 2025 |
| Dessian Products Limited | Manufacturing | 1985 |
| Destination CQ BID Ltd | Administrative & support | 2016 |
| Destination Financial Planning Limited | Financial services | 2015 |
| Detail Worx ALL Ireland Ltd | Wholesale & retail | 2025 |
| Devarc Limited | Real estate | 1999 |
| Devcap Limited | Information & communication | 2021 |
| Devcon NI Properties Ltd | Real estate | 2025 |
| Devcor Precast Ltd | Construction | 2011 |
| Developers Conference Limited | Administrative & support | 2022 |
| Development Trust Belfast CIC | Real estate | 2025 |
| Development Trusts (NI) Ltd | Professional & scientific | 2010 |
| Devend Ltd | Wholesale & retail | 2022 |
| Devenish (NI) Holdings Limited | Financial services | 2019 |
| Devenish (NI) Limited | Professional & scientific | 2007 |
| Devenish Co (Belfast) Ltd | Hospitality | 2015 |
| Devenish Holdings Limited | Professional & scientific | 2002 |
| Devenish Humanativ Limited | Financial services | 2021 |
| Devenish Nutrition (Turkey) Limited | Manufacturing | 2017 |
| Devenish Nutrition Investment Limited | Manufacturing | 2017 |
| Devenish Nutrition Limited | Manufacturing | 1952 |
| Devesky Ltd | Energy | 2014 |
| Devhub Ltd | Information & communication | 2020 |
| Device Link Traders Ltd | Wholesale & retail | 2026 |
| Devils Entertainment Ltd | Arts & recreation | 2014 |
| Devine and Associates Glassmullagh Ltd. | Mining & quarrying | 2007 |
| Devine Art Limited | Professional & scientific | 2024 |