| D a Hair Ltd | Other services | 2011 |
| D B Mclarnon Fire Protection Agency Ltd | Public administration | 2015 |
| D Bell Holdings Limited | Financial services | 2025 |
| D Black Consultancy Limited | Extraterritorial | 2023 |
| D Bryans Groundworks Ltd | Administrative & support | 2014 |
| D Buchanan Haulage (NI) Ltd | Transport & logistics | 2025 |
| D Christie Plumbing and Heating Ltd | Construction | 2023 |
| D Day Historical Trails Ltd | Administrative & support | 2025 |
| D Developments 1 LP | | 2017 |
| D Developments 2 Limited | Construction | 2017 |
| D Developments 3 Limited | Construction | 2017 |
| D E Autos (2023) Ltd | Wholesale & retail | 2023 |
| D E Landscapes Ltd | Administrative & support | 2024 |
| D Electrician Limited | Construction | 2024 |
| D K Armstrong Limited | Health & social care | 2020 |
| D M Tiling Belfast Ltd | Construction | 2024 |
| D M V Transport (N I ) Ltd | Transport & logistics | 2018 |
| D Marley Limited | Professional & scientific | 2018 |
| D Marlow Financial Limited | Professional & scientific | 2015 |
| D Mcalinden Ltd | Professional & scientific | 2012 |
| D Mcgranaghan Limited | Arts & recreation | 1965 |
| D Mckay Construction Limited | Construction | 2010 |
| D Mcmullan & Company Limited | Professional & scientific | 2012 |
| D Mcneilly Ltd | Other services | 2009 |
| D P EYE Care Ltd | Health & social care | 2014 |
| D R M Consultancy Limited | Other services | 2003 |
| D Sense Technologies Ltd | Professional & scientific | 2015 |
| D Smyth 88 Ltd | Hospitality | 2025 |
| D V V Cabling Ltd | Construction | 2003 |
| D W Middleton Health Ltd | Health & social care | 2024 |
| D&C Star Limited | Real estate | 2023 |
| D&E Flynn Haulage Ltd | Transport & logistics | 2017 |
| D&E Network Solutions Ltd | Construction | 2021 |
| D&G Corporate Catering Ltd | Hospitality | 2023 |
| D&J Healthcare Holdings Ltd | Financial services | 2026 |
| D&Jc Limited | Real estate | 2015 |
| D&M Services 2026 Ltd | Wholesale & retail | 2026 |
| D&S Baucon UK Limited | Construction | 2020 |
| D'Africart Commercial Stores Ltd | Wholesale & retail | 2023 |
| D'Or Essentials Ltd | Wholesale & retail | 2024 |
| D-Air Holdings Ltd | Real estate | 2025 |
| D-On Architects Ltd | Professional & scientific | 2004 |
| D-Translation Ltd | Professional & scientific | 2018 |
| D-Vine Belfast Ltd | Wholesale & retail | 2025 |
| D. & D. Flooring Limited | Construction | 1994 |
| D. Mccaffrey & Co. Limited | Real estate | 1988 |
| D.A. Wishart Contracts Limited | Construction | 2011 |
| D.A.B.C Logistic Limited | Wholesale & retail | 2022 |
| D.A.S.H. Books Ltd | Wholesale & retail | 2014 |
| D.C. Development & Planning (NI) Ltd | Extraterritorial | 1998 |
| D.D.K. Limited | Real estate | 1994 |
| D.F.P.F. Limited | Administrative & support | 2001 |
| D.G.&R.E. Beattie Limited | Manufacturing | 1974 |
| D.I.U. Management Limited | Real estate | 2008 |
| D.L.Kirkpatrick & SON Limited | Wholesale & retail | 1973 |
| D.M Property Estates Limited | Real estate | 2017 |
| D.T. Russell & Baird (Ireland) Limited | Wholesale & retail | 1968 |
| D1717 Limited | Construction | 2018 |
| D2 Property Investments Limited | Real estate | 2018 |
| D2D International Company Limited | Wholesale & retail | 2025 |
| D2D Trading Limited | Wholesale & retail | 2013 |
| D3 Properties Limited | Construction | 2007 |
| D3I Developments Ltd | Construction | 2016 |
| D3I Projects Ltd | Real estate | 2021 |
| D3RK Matter Limited | Information & communication | 2015 |
| D4 Property Investments Limited | Real estate | 2019 |
| D7 Limited | Manufacturing | 2022 |
| Dabs Distribution Limited | Wholesale & retail | 1907 |
| DAC Beachcroft (N.Ireland) LLP | | 2018 |
| Dacinoa Ltd | Wholesale & retail | 2020 |
| Dack Estates Limited | Real estate | 1977 |
| Dadaf Property Ltd | Real estate | 2024 |
| Dadanliya Ltd | Wholesale & retail | 2026 |
| Dadashia Limited | Hospitality | 2024 |
| Dadbods Community NI Limited | Health & social care | 2025 |
| Dadbodsni CIC | Other services | 2023 |
| Daddy PIG Limited | Wholesale & retail | 2015 |
| Dado Consulting Limited | Information & communication | 2015 |
| Dado Developments Ltd | Real estate | 1988 |
| Daesar Trading Co. Limited | Wholesale & retail | 2025 |
| Daeves LP | | 2021 |
| DAG Property Investments Ltd | Real estate | 2026 |
| Dagger Productions Ltd | Arts & recreation | 2024 |
| Daiigg LAN Ltd | Wholesale & retail | 2025 |
| Daijay Limited | Wholesale & retail | 2024 |
| Daily Assembly Limited | Wholesale & retail | 2026 |
| Daily Mirror Newspapers, Limited - the | | 1968 |
| Dailypay (NI) Ltd | Information & communication | 2021 |
| Daimon Limited | Wholesale & retail | 2025 |
| Dairy Council for Northern Ireland - the | Other services | 1956 |
| Dairy Farm Tyres Limited | Wholesale & retail | 2015 |
| Daisy Care Support Services Ltd | Health & social care | 2025 |
| Daisy Chantal Investment Ltd | Wholesale & retail | 2023 |
| Daisy Day Care N.I. Limited | Health & social care | 2021 |
| Daisy Films Limited | Information & communication | 2024 |
| Daisy O'Neills Ltd | Manufacturing | 2016 |
| Daisy Phan Beauty Ltd | Other services | 2025 |
| Daisyworx Business Consultants Ltd | Information & communication | 2024 |
| DAJ Designs Limited | Professional & scientific | 2001 |
| Dakota Carry LLP | | 2017 |