| DL Graphics Design Ltd | Professional & scientific | 2016 |
| DLL Properties Limited | Construction | 2012 |
| DLM Rentals Ltd | Households | 2025 |
| Dluf Radiology Ltd | Health & social care | 2026 |
| DM Autos (NI) Ltd | Wholesale & retail | 2025 |
| DM Inspect Ltd | Construction | 2017 |
| DM Maintenance Joinery Limited | Manufacturing | 2024 |
| DM MPS Property Limited | Real estate | 2016 |
| DM PFI and Commercial Services Limited | Professional & scientific | 2023 |
| DM Services Fulfilment Ltd | Other services | 2026 |
| DM Timber Ltd | Wholesale & retail | 2012 |
| DM Wind Ltd | Manufacturing | 2024 |
| DMA Joinery N.I. Ltd | Construction | 2026 |
| Dmac GAS Services Ltd | Construction | 2022 |
| DMB Consult&Train(Ni) Ltd | Professional & scientific | 2026 |
| Dmbm Holdings Ltd | Financial services | 2022 |
| DMC Elect. Limited | Construction | 2017 |
| DMC Group Ltd | Water & waste | 2018 |
| DMC Skip & Waste Ltd | Water & waste | 2026 |
| Dmca Property Ltd | Real estate | 2022 |
| Dmcg Commerce Limited | Wholesale & retail | 2024 |
| Dmck Medical Consulting Limited | Health & social care | 2025 |
| DMD (Belfast) Ltd | Wholesale & retail | 2021 |
| DMD Holdings (Belfast) Ltd | Financial services | 2024 |
| DMD Rigging Limited | Financial services | 2023 |
| DMG Financial Services Ltd | Professional & scientific | 2021 |
| DMG Flooring Ltd | Wholesale & retail | 2021 |
| Dmgl Properties Limited | Real estate | 2023 |
| DMK Construction Limited | Construction | 2004 |
| DMK Distribution (NI) Ltd | Wholesale & retail | 2018 |
| Dmn-Ubni Ltd | Arts & recreation | 2022 |
| Dmoore Properties Ltd | Real estate | 2016 |
| DMR Group Ltd | Information & communication | 2026 |
| DMR Physio Services Ltd | Administrative & support | 2013 |
| DMS Homecare Ltd | Wholesale & retail | 2026 |
| DMT Investments Limited | Real estate | 2025 |
| DMW Accountants (2011) Limited | Professional & scientific | 2011 |
| DMW Taxation Ltd | Professional & scientific | 2018 |
| DMX Limited | Professional & scientific | 2018 |
| Dnanhuangd Ltd | Wholesale & retail | 2025 |
| DNM Property Investments Ltd | Real estate | 2019 |
| DNR Aviation Limited | Manufacturing | 2024 |
| Dntca Accounting Ltd | Professional & scientific | 2024 |
| Dntca Audit Ltd | Professional & scientific | 2025 |
| Dntca Ltd | Professional & scientific | 2005 |
| DO YOU Female Only Gym Ltd | Arts & recreation | 2025 |
| Doagh Farm Ltd | Real estate | 2020 |
| Doagh Metals Ltd | Construction | 2018 |
| DOC Global Ltd | Wholesale & retail | 2023 |
| Doce Retail Limited | Wholesale & retail | 2019 |
| Docent Limited | Wholesale & retail | 2025 |
| Dock Ward Estates Limited | Real estate | 1994 |
| Dockview Ventures Limited | Professional & scientific | 2026 |
| Doctor Parke Ltd | Health & social care | 2024 |
| Docujet Ltd | Manufacturing | 2003 |
| Docuscan Africa Limited | Information & communication | 2021 |
| Dodoma Ventures Limited | Energy | 2017 |
| DOF Developments Ltd | Construction | 2021 |
| Dog Shack Studio Ltd | Information & communication | 2026 |
| Dogs Zone (NI) Ltd | Other services | 2024 |
| Doherty Architects Limited | Professional & scientific | 2012 |
| Doherty Developments Limited | Construction | 1990 |
| Doherty Labs Ltd | Information & communication | 2023 |
| Doherty Pension & Investment Consultancy Limited | Administrative & support | 1997 |
| Doineann Ltd | Information & communication | 2019 |
| Doirnin Management Company Ltd | Households | 2013 |
| Dokane Design Ltd | Professional & scientific | 2022 |
| Dokoo Limited | Information & communication | 2012 |
| Dolajib Services Limited | Health & social care | 2022 |
| Dolan FIC Ltd | Financial services | 2026 |
| Dolcis Limited | | 1996 |
| Dole Belfast Limited | Wholesale & retail | 1952 |
| Dolgan Properties Limited | Real estate | 2002 |
| Dollvision Media Ltd | Information & communication | 2024 |
| Dolmen Diagnostics Limited | Professional & scientific | 2023 |
| Dolmen Park Management Co. Ltd | Households | 2010 |
| Dolmen Pictures Limited | Information & communication | 2023 |
| Dolmen Services Ltd | Construction | 2017 |
| Dolphin Hub Limited | Wholesale & retail | 2024 |
| Dolphin Sub-Aqua Limited | Arts & recreation | 2010 |
| DOM Consultants Limited | Professional & scientific | 2011 |
| Dominic Braniff Ltd | Manufacturing | 2022 |
| Dominic Emanuel Consulting Ltd | Information & communication | 2019 |
| Dominic Smith Electrical NI Limited | Wholesale & retail | 2024 |
| Dominion City Belfast Ltd | Other services | 2025 |
| Dominum Group LP | | 2019 |
| Domus Portfolio Ltd | Financial services | 2021 |
| Domusprime Property Ltd | Real estate | 2026 |
| DON Delivers Ltd | Transport & logistics | 2024 |
| DON Design Services Ltd | Professional & scientific | 2015 |
| DON Lusso Ltd | Wholesale & retail | 2021 |
| DON Mcqueen Office Interiors and Specialist Seating Ltd | Wholesale & retail | 2013 |
| Donaghadee Properties Ltd | Real estate | 2015 |
| Donaghcloney GP Practice C.I.C. | Health & social care | 2023 |
| Donaghey & Chance Ltd | Professional & scientific | 2021 |
| Donaghy Carey Solicitors Limited | Professional & scientific | 2018 |
| Donal Mccann Photography Ltd | Professional & scientific | 2018 |
| Donal Mcevoy Ltd | Health & social care | 2024 |
| Donaldson and Lyttle Property Ltd | Construction | 2016 |
| Donard Capital Limited | Professional & scientific | 2017 |