| Cullion Wind Farm Limited | Energy | 2020 |
| Cunningham Stone Limited | Manufacturing | 2023 |
| Curtina Limited | Extraterritorial | 2000 |
| Curve Training and Consultancy Limited | Construction | 2020 |
| Custom Finishing (NI) Limited | Wholesale & retail | 2018 |
| Custom Productions Limited | Information & communication | 2019 |
| CUT & Grind Salon Ltd | Other services | 2020 |
| Cuteryko Ltd | Manufacturing | 2024 |
| Cuthbert (NI) Limited | Administrative & support | 2012 |
| Cuttin About Group Ltd | Arts & recreation | 2024 |
| Cutting & Welding NI Ltd | Wholesale & retail | 2018 |
| Cutweld Ltd | Wholesale & retail | 2026 |
| CW Accountancy Services Limited | Professional & scientific | 2009 |
| CWD Distributions Ltd | Wholesale & retail | 2025 |
| CWS Design Limited | Construction | 2005 |
| D & G Reid Company Limited | Agriculture & fishing | 2014 |
| D & J Generators Limited | Manufacturing | 2003 |
| D & M Cakes Limited | Wholesale & retail | 1995 |
| D F Ross & Sons Limited | Wholesale & retail | 1982 |
| D G Green & Sons Limited | Construction | 2016 |
| D. C. Drains Ltd | Water & waste | 2017 |
| Dairyside Feeds Limited | Wholesale & retail | 2021 |
| Daletree Properties Limited | Households | 2025 |
| Dalmar Holdings Ltd | Real estate | 2021 |
| Damar Consulting (NI) Ltd | Extraterritorial | 2002 |
| Damask Community Outreach | Health & social care | 2011 |
| Daniel Greenan Photo & Video Limited | Professional & scientific | 2024 |
| Dansa - the Studio Belfast Limited | Arts & recreation | 2021 |
| Dante Creative Limited | Professional & scientific | 2016 |
| Dark Earth Ltd | Professional & scientific | 2018 |
| Darrin Wilson Ltd | Health & social care | 2012 |
| Darson Services Ltd | Construction | 1999 |
| Data Freeport Ltd | Information & communication | 2021 |
| Datum Enterprises Limited | Financial services | 2021 |
| Datum Tool Design Ltd | Professional & scientific | 1998 |
| Davetree LP | | 2019 |
| David Mcgrory Limited | Manufacturing | 2015 |
| Davis Developments N.I. Ltd | Construction | 2006 |
| Davis Marketing Solutions Ltd | Professional & scientific | 2025 |
| Dazed Holdings Ltd | Wholesale & retail | 2023 |
| DB Industrial Services Ltd | Manufacturing | 2022 |
| DC4MECHANICAL& Construction Ltd | Construction | 2018 |
| DD Contracts(Ni) Ltd | Construction | 2020 |
| DE Romein Nearshore Ltd. | Construction | 2022 |
| Debitrak Cashless Payment Systems Limited | Information & communication | 2015 |
| Decor Ireland Ltd | Wholesale & retail | 2011 |
| Deep International Ocean LLP | | 2019 |
| Deep River Media Ltd | Information & communication | 2023 |
| Deforp Corp. LP | | 2022 |
| Dejm Holdings Limited | Financial services | 2025 |
| Dejm Limited | Financial services | 2025 |
| Dejm Properties Limited | Financial services | 2025 |
| DEL Toro Limited | Hospitality | 2015 |
| Delta Claims (NI) Ltd | Financial services | 2015 |
| Dempsey Property Holdings Limited | Real estate | 2025 |
| Dennison Electrical Limited | Construction | 2004 |
| Derry Bros Shipping Limited | Transport & logistics | 2005 |
| DES Cairns Architecture Ltd | Professional & scientific | 2017 |
| DES Ewing Architects Limited | Professional & scientific | 2020 |
| Desmond Eastwood Motors Ltd | Wholesale & retail | 1999 |
| Develamo Ltd | Information & communication | 2022 |
| Devineair Limited | Professional & scientific | 2013 |
| Dexter Management Associates LLP | | 2017 |
| Dfcm Limited | Professional & scientific | 2021 |
| DFK International Consulting Group Limited | Extraterritorial | 2001 |
| DG Financial Wealth Ltd | Financial services | 2014 |
| Dghm Group Ltd | Construction | 2017 |
| Dickson Plant Hire & Groundworks Limited | Construction | 2013 |
| Digicom Trading Ltd | Information & communication | 2021 |
| Digital Fire & Security (NI) Limited | Administrative & support | 2004 |
| Digital Wiring Ltd | Information & communication | 1997 |
| Dijke Limited | Wholesale & retail | 2025 |
| Dillon Contracts Ltd | Construction | 2025 |
| Direct European Limited | Transport & logistics | 2001 |
| Discount Blinds and Furniture Limited | Manufacturing | 2014 |
| Divinity Bridal Limited | Wholesale & retail | 2026 |
| DJM Aerospace Ltd | Manufacturing | 2018 |
| Dlrt Limited | Manufacturing | 1986 |
| DM Flooring Holdings Limited | Construction | 2025 |
| DM Laser-Fab Limited | Manufacturing | 2010 |
| DM Laser-Fab Resources Limited | Administrative & support | 2025 |
| Dmacweld Limited | Manufacturing | 1977 |
| DMB (N.I.) Ltd | Wholesale & retail | 2017 |
| DMC Rentals Limited | Real estate | 2022 |
| Dmcc Agencies Limited | Wholesale & retail | 2018 |
| DMG Surgical Limited | Health & social care | 2023 |
| Dmhft Limited | Professional & scientific | 2012 |
| Dmic Solutions Limited | Information & communication | 2025 |
| Dntla Limited | Professional & scientific | 2013 |
| DO YOU Online Ltd | Arts & recreation | 2023 |
| Dobbin Refrigeration Services Limited | Manufacturing | 2004 |
| Dodds Properties (N.I.) Limited | Real estate | 2016 |
| Dolly's Yard Limited | Agriculture & fishing | 2012 |
| Donaldson Mcconnell & Co Ltd | Professional & scientific | 2016 |
| Donegall Rise Management Limited | Households | 2023 |
| Donibristle Developments Limited | Construction | 1996 |
| Donibristle Trust | Professional & scientific | 2000 |
| Donnan Ward Limited | Professional & scientific | 2011 |
| Dorman Rentals Ltd | Real estate | 2025 |
| Dorman Storage Ltd | Transport & logistics | 2026 |