| Devio Ltd | Information & communication | 2025 |
| Devise Digital Ltd | Information & communication | 2013 |
| Devlin Brown Holdings Ltd | Real estate | 2026 |
| Devlin Upholstery & Interiors Ltd | Manufacturing | 2026 |
| Devnest Media Ltd | Information & communication | 2026 |
| Dextericgames Ltd | Information & communication | 2021 |
| DF Electrical Group Ltd | Construction | 2026 |
| Dfinaca Qing Ltd | Wholesale & retail | 2025 |
| Dfiu Limited | Other services | 2017 |
| DFJ Investments | Financial services | 2021 |
| Dfpf Employees' Trustees Ltd | Extraterritorial | 2024 |
| Dfpf Property LLP | | 2009 |
| Dfrni Ltd | Professional & scientific | 2015 |
| DG (Ireland) Ltd | Information & communication | 2015 |
| DG Aero Systems Limited | Information & communication | 2016 |
| DG Anaesthetics Limited | Health & social care | 2019 |
| DG Fortis Ltd | Administrative & support | 2025 |
| DG GAS Limited | Construction | 2025 |
| DG GAS Safety Ltd | Construction | 2016 |
| DG House Ltd | Hospitality | 2025 |
| DG Software Consulting Limited | Information & communication | 2023 |
| DGM Fitness Ltd | Arts & recreation | 2024 |
| DGM Medicolegal Ltd | Professional & scientific | 2025 |
| DGR Food Limited | Real estate | 2020 |
| DGS Property Services Ltd | Construction | 2025 |
| DGS Service Solutions Limited | Administrative & support | 2013 |
| DH Europe Ltd | Manufacturing | 2016 |
| DH Ireland Limited | Hospitality | 2024 |
| DH Partners NI Ltd | Information & communication | 2025 |
| DH Rentals RS Limited | Real estate | 2021 |
| DH3 Games Ltd | Information & communication | 2017 |
| Dhaatri Ltd | Wholesale & retail | 2025 |
| Dhaka Spice Belfast Ltd | Hospitality | 2018 |
| Dhali Holdings Ltd | Information & communication | 2023 |
| Dhiksha Ltd | Information & communication | 2011 |
| DHM Gill Transport Limited | Professional & scientific | 2025 |
| Dhmc Contracts Limited | Construction | 2020 |
| Dhoyo Byudh Ltd | Wholesale & retail | 2025 |
| DHR Energy Limited | Administrative & support | 2024 |
| DIA Beta Labs Ltd | Professional & scientific | 2022 |
| Diabetes Performance Coaching | Education | 2016 |
| Diaceutics PLC | Professional & scientific | 2005 |
| Diageo Global Supply IBC Limited | Wholesale & retail | 1951 |
| Diageo Northern Ireland Limited | Wholesale & retail | 1956 |
| Dialsave Limited | Information & communication | 2019 |
| Diamond & Skillen Limited | Professional & scientific | 2002 |
| Diamond (Belfast) Limited | Professional & scientific | 2006 |
| Diamond Bliss & Gemstone Co Ltd | Wholesale & retail | 2022 |
| Diamond Bright Cleaning NI Ltd | Administrative & support | 2016 |
| Diamond Chauffeurs Ireland Ltd | Transport & logistics | 2019 |
| Diamond Cleaning Co N.I. Ltd | Construction | 2023 |
| Diamond Cleaning Services Belfast Ltd | Administrative & support | 2026 |
| Diamond Cleaning Training Academy NI Ltd | Education | 2025 |
| Diamond Contract Solutions Ltd | Construction | 2017 |
| Diamond Domestic N.I. Ltd | Administrative & support | 2025 |
| Diamond Electronic Systems Limited | Administrative & support | 1993 |
| Diamond Global Trading & Investments Ltd | Construction | 2011 |
| Diamond Joint Ventures Ltd | Public administration | 2025 |
| Diamond Leisure Transport Limited | Transport & logistics | 2009 |
| Diamond Nails & Spa 99 Ltd | Other services | 2024 |
| Diamond Orthopaedics Ltd | Health & social care | 2020 |
| Diamond Prism Limited | Professional & scientific | 2026 |
| Diamond Rose Ltd | | 2001 |
| Diamond Stella 6 Ltd | Other services | 2024 |
| Diana Ennis Limited | Arts & recreation | 2023 |
| Diane Limited | Wholesale & retail | 2025 |
| Diane Sweeney Ltd | Wholesale & retail | 2022 |
| Dicey Reilly's Limited | Hospitality | 2013 |
| Dickson and Sons Ltd | Financial services | 2024 |
| Dickson Contracting Ltd | Information & communication | 2015 |
| Dickson Fitzgerald Architects Ltd | Professional & scientific | 2014 |
| Dicromed Ltd | Health & social care | 2017 |
| Didactic Systems (NI) Limited | Professional & scientific | 2017 |
| Diec Ltd | Real estate | 2021 |
| Dieci IT Solutions Ltd | Professional & scientific | 2024 |
| Diego Armanfe Ltd | Manufacturing | 2024 |
| Dielianhua Limited | Wholesale & retail | 2023 |
| Difa Limited | Construction | 2017 |
| DIG Deep Coaching Ltd | Arts & recreation | 2011 |
| Digi Know This Ltd | Professional & scientific | 2024 |
| Digi Skills Agency Ltd | Information & communication | 2022 |
| Digi-Pop Games Ltd. | Information & communication | 2014 |
| Digiart Industry Limited | Manufacturing | 2025 |
| Digirize Solutions PVT Ltd | Information & communication | 2015 |
| Digital Advertising Solutions NI Limited | Professional & scientific | 2010 |
| Digital Array Control Systems (NI) Ltd | Professional & scientific | 2021 |
| Digital Arts Studios | Arts & recreation | 2008 |
| Digital Automation and Robotics Limited | Information & communication | 2020 |
| Digital Brokers Group Ltd | Financial services | 2020 |
| Digital Camera Hire Limited | Other services | 2016 |
| Digital Care Systems Limited | Information & communication | 2018 |
| Digital Dermpath Diagnostics Ltd | Health & social care | 2025 |
| Digital Excellence Ltd | Information & communication | 2018 |
| Digital Forensics Ireland Limited | Professional & scientific | 2017 |
| Digital Industry Consulting Ltd | Information & communication | 2018 |
| Digital Infrastructure Partners Limited | Professional & scientific | 2023 |
| Digital Iron Ltd | Information & communication | 2025 |
| Digital Land Ltd | Wholesale & retail | 2025 |
| Digital Leopards Agency Ltd | Information & communication | 2025 |
| Digital Strada Ltd | Information & communication | 2025 |