| DC & Daughters Properties Ltd | Real estate | 2023 |
| DC & SG Holdings Limited | Financial services | 2024 |
| DC Design Services Ltd | Professional & scientific | 2026 |
| DC Enterprises (N.I.) Limited | Wholesale & retail | 2025 |
| DC EV Leasing Limited | Administrative & support | 2021 |
| DC Hunter Medical Ltd | Health & social care | 2014 |
| DC INK Ltd | Arts & recreation | 2023 |
| DC Operations Limited | Real estate | 2004 |
| DC Services Joinery & Property Maintenance Ltd | Manufacturing | 2019 |
| DC Traders Limited | Hospitality | 2016 |
| DC Tyres & Exhausts Ltd | Wholesale & retail | 2023 |
| DC Wines Ltd | Wholesale & retail | 2019 |
| DC2 Sports Ltd | Wholesale & retail | 2019 |
| DC4 Training Ltd | Construction | 2019 |
| DCC Energy Ltd | Wholesale & retail | 1974 |
| Dccl Housing Ltd | Transport & logistics | 2025 |
| DCI Energy Control Limited | Construction | 1994 |
| DCL Holdings (N.I.) Ltd | Professional & scientific | 2022 |
| Dclm Property Ltd | Real estate | 2024 |
| DCM Cooling Limited | Energy | 2021 |
| DCM Costs Limited | Professional & scientific | 2019 |
| Dconn Property Limited | Real estate | 2021 |
| DCS Contract Services Ltd | Construction | 2025 |
| Dcsc Limited | Manufacturing | 2024 |
| Dcsni Limited | Professional & scientific | 2013 |
| DCV Technologies Ireland Ltd | Information & communication | 2025 |
| DD (Ireland) Limited | Construction | 2015 |
| Ddna Ltd | Professional & scientific | 2015 |
| Ddnp Holdings Limited | Real estate | 2015 |
| DDS Retail Solutions Limited | Wholesale & retail | 2020 |
| Ddsli NSA Ltd | Wholesale & retail | 2024 |
| DDW Trade L.P. | | 2017 |
| Ddzweenn Ltd | Wholesale & retail | 2025 |
| DE Courcey Mews Management Co Ltd | Real estate | 2018 |
| DE Luca Luca Ltd | Wholesale & retail | 2025 |
| DE Zanche Valentina Ltd | Wholesale & retail | 2025 |
| De&Dm Ltd | Construction | 2021 |
| Dead on Mafia Media Ltd | Information & communication | 2022 |
| Deaf Access NI Limited | Professional & scientific | 2024 |
| Deal Dice Ltd | Wholesale & retail | 2025 |
| Deal IT Consulting & Services Limited | Information & communication | 2017 |
| Deal IT Properties Limited | Real estate | 2025 |
| Dealpush Ltd | Wholesale & retail | 2023 |
| Dealvalue Technology Ltd | Wholesale & retail | 2022 |
| Deamagem Contracting LLP | | 2012 |
| Debeere Court Limited | Extraterritorial | 1987 |
| Deborah Boyle Medical Aesthetics Limited | Other services | 2025 |
| Deborah Magill Limited | Wholesale & retail | 2023 |
| Debrenn Limited | Professional & scientific | 2006 |
| Debt Control Limited | Financial services | 2005 |
| Debtchoice.Co.Uk Ltd | Financial services | 2024 |
| Debugvc Ltd | Professional & scientific | 2023 |
| DEC Ward Barber Shop Limited | Other services | 2026 |
| Deca Ltd | Financial services | 2026 |
| Decagon Properties Limited | Real estate | 2013 |
| Decarb MEP Limited | Manufacturing | 2024 |
| Decho Pinink Limited | Wholesale & retail | 2025 |
| Declan MEE Ltd | Water & waste | 2010 |
| Declan O’Rourke Uropathology Ltd | Health & social care | 2019 |
| Declaron Custom Clearance Limited | Public administration | 2020 |
| Decom Engineering Ltd | Manufacturing | 2011 |
| Decorative Arts Company Limited | Professional & scientific | 2004 |
| Decorators Touch Belfast Limited | Wholesale & retail | 2011 |
| Decowell Restoration Ltd | Real estate | 2017 |
| Decrescent Limited | Wholesale & retail | 2025 |
| Dedalus Bloom Ltd | Professional & scientific | 2023 |
| Deeny Communications Limited | Professional & scientific | 2025 |
| Deep Edge Ltd | Wholesale & retail | 2025 |
| Deep Labs Ltd | Professional & scientific | 2017 |
| Deepagent Limited | Information & communication | 2025 |
| Deepaint Technology Co Limited | Wholesale & retail | 2023 |
| Deepdock Shellfish Ltd | Agriculture & fishing | 2022 |
| Deeply Armed Limited | Arts & recreation | 2015 |
| Deerah Ltd | Hospitality | 2021 |
| Deerpark Lands Limited | Construction | 2017 |
| Dees Trainers Ltd | Wholesale & retail | 2026 |
| Default Development Limited | Information & communication | 2022 |
| Defendnet Technology Limited | Extraterritorial | 2025 |
| Defendoors Ltd | Manufacturing | 2010 |
| Deirdre Rooney Ltd | Health & social care | 2023 |
| Deko Maker Limited | Wholesale & retail | 2025 |
| Deku Tats Ltd | Other services | 2023 |
| DEL Boy's Dirty Work Ltd | Administrative & support | 2025 |
| DEL Suelo Limited | Wholesale & retail | 2023 |
| Delamount Properties Limited | Households | 2001 |
| Delanie Daily Limited | Wholesale & retail | 2024 |
| Delegate Recruitment Limited | Administrative & support | 2009 |
| Delfina SA Ltd | Wholesale & retail | 2023 |
| Deli-Lites (Newry) Limited | Hospitality | 2000 |
| Delicate Crystal Ltd | Wholesale & retail | 2024 |
| Delicate Day Limited | Wholesale & retail | 2024 |
| DELIGHT4U Ltd | Health & social care | 2023 |
| Deliver to YOU NI Ltd | Transport & logistics | 1987 |
| Delivery Services & Storage Limited | Other services | 2013 |
| Deliverynow Ltd | Wholesale & retail | 2023 |
| Delizia Ltd | Hospitality | 2019 |
| Deloitte (NI) Limited | Professional & scientific | 2015 |
| Deloitte Ireland LLP | | 2018 |
| Delprop Limited | Hospitality | 2021 |
| Delta 7 Systems Ltd | Information & communication | 2026 |