| CT Plumbing & Heating Limited | Construction | 2016 |
| Cuilcagh Ltd | Real estate | 2021 |
| Cullen Developments Ltd | Real estate | 2020 |
| Cullen Plastering Ltd | Construction | 2017 |
| Cully Developments Limited | Construction | 2005 |
| Cully FS Ltd | Real estate | 2023 |
| Culmore Service Station Limited | Wholesale & retail | 2016 |
| Culmore Services NI Limited | Wholesale & retail | 2022 |
| Cunningham and Associates, Marine and Civil Engineering Quantity Surveyor Limited | Construction | 2025 |
| Curr Holdings Ltd | Financial services | 2020 |
| Curragh Developments 1 Ltd | Real estate | 2025 |
| Curragh Holdings Limited | Financial services | 2024 |
| Curran Architecture Solutions Ltd | Information & communication | 2015 |
| Custom Contracts and Construction Ltd | Construction | 2022 |
| Cxxxv Ltd | Arts & recreation | 2024 |
| Cyber Network Ltd | Wholesale & retail | 2021 |
| D & K Finance Ltd | Financial services | 2023 |
| D & S Acquisitions (UK) Ltd | Wholesale & retail | 2014 |
| D O Mccracken & Sons Ltd | Agriculture & fishing | 2015 |
| D Sloane Engineering & Construction Ltd | Professional & scientific | 2023 |
| D Smyth Trading (NI) Ltd | Wholesale & retail | 2025 |
| D&A NI Holdings Ltd | Financial services | 2021 |
| D&M Mcbride Ltd | Construction | 2006 |
| D&S Grimes Poultry Ltd | Agriculture & fishing | 2012 |
| D. a. Mclernon Ltd | Real estate | 2016 |
| D. O'Neill Architectural & Design Services Limited | Professional & scientific | 2003 |
| D. Walls Electrical Limited | Construction | 2020 |
| D.D. Aesthetics NI Ltd | Other services | 2026 |
| DAC Appliances Limited | Wholesale & retail | 2010 |
| Dadra Limited | Manufacturing | 2009 |
| Daire Consultants Ltd | Administrative & support | 2013 |
| Dairy Services & Spares Ltd | Agriculture & fishing | 2025 |
| Dalcat Ltd | Health & social care | 2024 |
| Dalmell Properties Ltd | Real estate | 2013 |
| Dalmon Ltd | Real estate | 2023 |
| Dalradian Gold Limited | Mining & quarrying | 1971 |
| Dalton Property Solutions Ltd | Real estate | 2025 |
| Daly Contracts Ltd | Construction | 2025 |
| Daly Property Group Ltd | Construction | 2023 |
| Daly Real Estate Limited | Real estate | 2020 |
| Daly Retail Limited | Wholesale & retail | 2017 |
| Dalys Carrickmore Ltd | Wholesale & retail | 2012 |
| Damac Contracts Ltd | Construction | 2011 |
| Damac Plant Hire & Sales Ltd | Financial services | 2025 |
| Daneen Trading Co Limited | Wholesale & retail | 2024 |
| Daniel Mccrory Ltd | Arts & recreation | 2020 |
| Dankoa Construction Ltd | Real estate | 2021 |
| Darcy Bros Ltd | Manufacturing | 2011 |
| Darcy Professional Services Ltd | Construction | 2018 |
| Darlex Trading Co Ltd | Wholesale & retail | 2019 |
| Darren Farming | Agriculture & fishing | 2017 |
| David Mcmaster Electrical Limited | Construction | 2011 |
| Daytona Haulage UK Limited | Transport & logistics | 2018 |
| DBB Holdings Limited | Financial services | 2022 |
| DBF International Ltd | Transport & logistics | 2023 |
| Dbox Accessories Ltd | Wholesale & retail | 2020 |
| Dbox Vape Ltd | Wholesale & retail | 2020 |
| DCL Car Specialists Ltd | Wholesale & retail | 2021 |
| DCM (Omagh) Ltd | Professional & scientific | 2016 |
| Dcyc Limited | Construction | 2017 |
| Ddon Construction Limited | Construction | 2018 |
| Deans Trade Solutions Ltd | Wholesale & retail | 2022 |
| Decky Contracts Limited | Construction | 2006 |
| Decky Holdings Ltd | Financial services | 2022 |
| Decky Properties Ltd | Real estate | 2018 |
| Declan Mclaughlin Ltd | Construction | 2012 |
| Deedy Technology Limited | Information & communication | 2019 |
| Dehg Properties Ltd | Real estate | 2026 |
| DEL Loughran Hair & Beauty Limited | Other services | 2018 |
| Demeter Harvest Ltd | Agriculture & fishing | 2014 |
| Denamona Properties Ltd | Construction | 2014 |
| Denis Barrett Auctions Ltd | Wholesale & retail | 2023 |
| Denis Connolly Joinery Limited | Construction | 2017 |
| Derg and District Community and Cultural Development Limited | Health & social care | 2024 |
| Derg Eoin Property Holdings Limited | Financial services | 2021 |
| Dergmoney Consultants Ltd | Professional & scientific | 2023 |
| Dergmoney Ltd | Construction | 2015 |
| Dergmoney Medical Limited | Health & social care | 2021 |
| Dergmoney Properties Limited | Construction | 2017 |
| Dergview Football Club Limited | Arts & recreation | 1999 |
| Derry & Raphoe Action Limited | Administrative & support | 2003 |
| Dervala Energy Limited | Professional & scientific | 2021 |
| DES Flanagan Investment Solutions Ltd | Financial services | 2012 |
| Deslan Investments Limited | Financial services | 1997 |
| Devine Haulage Ltd | Transport & logistics | 2025 |
| Devine Sand & Gravel Limited | Mining & quarrying | 1995 |
| Devity Contract Services Limited | Construction | 2018 |
| Dickson & Co (NI) Limited | Financial services | 2009 |
| Dickson & Co Properties Limited | Real estate | 2014 |
| Dickson Family Holdings Limited | Financial services | 2020 |
| Dickson Farm Limited | Agriculture & fishing | 2021 |
| Dickson Group London Market Ltd | Financial services | 2025 |
| Difco Limited | Manufacturing | 2013 |
| Diggermats Limited | Construction | 2012 |
| Digital Drive Ltd | Information & communication | 2018 |
| Dimac Sports Grounds Limited | Administrative & support | 2014 |
| Direct Heat (NI) Limited | Construction | 2004 |
| Dirt Bike Tours (IRL) Limited | Wholesale & retail | 2013 |
| DJC Maintenance Ltd | Manufacturing | 2015 |
| DJC Poultry Ltd | Agriculture & fishing | 2013 |