| Colin Graham Music Ltd | Information & communication | 2026 |
| Colin Patton & SON Ltd | Wholesale & retail | 2021 |
| Colinvale House Management Company Limited | Extraterritorial | 2004 |
| College Central Management Company Limited | Extraterritorial | 2006 |
| Comfort Heat Ltd | Construction | 2024 |
| Commercial Vehicle Spares Limited | Wholesale & retail | 1998 |
| Commonly Written Ltd | Information & communication | 2024 |
| Complete Car Care Solutions Ltd | Other services | 2015 |
| Complete Skin & Laser Clinic Limited | Other services | 2023 |
| Comsales Marketing Limited | Professional & scientific | 2017 |
| Coneyville Management Company Ltd | Households | 2019 |
| Connect Fitness Limited | Arts & recreation | 2019 |
| Connected Compliance Solutions Limited | Information & communication | 2024 |
| Connor Building Services Limited | Financial services | 2019 |
| Consulted (NI) Ltd | Real estate | 2011 |
| Continu Energy Ltd | Manufacturing | 2025 |
| Continu Ltd | Manufacturing | 2010 |
| Coolhut Products Ltd | Wholesale & retail | 2023 |
| Coopman UK Limited | Administrative & support | 2022 |
| Corran Mews Management Co. Ltd | Households | 2011 |
| Corry Capital Holdings Ltd | Information & communication | 2023 |
| Cotton Hall Management Company Limited | Households | 2019 |
| Cotton Mount Management Company Limited | Households | 2017 |
| Cottonmill Green Management Company Limited | Real estate | 2022 |
| Coulter Corporate Limited | Professional & scientific | 2015 |
| Cove Close Ballyronan Ltd | Extraterritorial | 2003 |
| Cpnh Contracts Ltd | Health & social care | 2023 |
| Craigstown Meadow Management Ltd | Extraterritorial | 2001 |
| Cranny Oaks Management Company Ltd | Households | 2018 |
| Crawford Contracts Ltd | Construction | 2021 |
| Crawford Media Works Ltd | Arts & recreation | 2025 |
| Crazy Prices Limited | Wholesale & retail | 2019 |
| Creatembm Ltd | Real estate | 2023 |
| Crecora House Management Company Limited | Households | 2005 |
| Cronnellys Roofing and Cladding (U.K.) Limited | | 1980 |
| Crumlin Road Retail Ltd | Wholesale & retail | 2015 |
| CTL Couriers Limited | Transport & logistics | 2017 |
| CYM Properties Ltd | Construction | 2012 |
| D C Packaging Tapes Limited | Manufacturing | 2008 |
| D L Wilson Haulage Ltd | Transport & logistics | 2011 |
| D&G Hunter Developments Limited | Real estate | 2006 |
| D4 Ltd | Professional & scientific | 1999 |
| D4 Vintage Ltd | Other services | 2022 |
| Dace Properties Limited | Real estate | 2000 |
| Dancall Ltd | Real estate | 2024 |
| Danesfort Management Company Limited | Households | 2000 |
| Dannange Ltd | Real estate | 2020 |
| Dawson Digital Ltd | Professional & scientific | 2024 |
| Dawson's Hill Management Company Limited | Households | 2019 |
| Daykin & Scott Dog Training & Behaviour Services Ltd | Education | 2021 |
| DB Build (N.I.) Ltd | Construction | 2019 |
| DCP Strategic Communication Ltd | Professional & scientific | 1985 |
| Dead on Darts Ltd | Wholesale & retail | 2026 |
| Deca Design Bureau Ltd | Professional & scientific | 2014 |
| Deja Brew Limited | Wholesale & retail | 2016 |
| Dekah NI Limited | Wholesale & retail | 2022 |
| Dennpart Limited | Wholesale & retail | 2024 |
| Denorrton Manor Management Co Ltd | Households | 2020 |
| Derrychrin Management Company Limited | Households | 2006 |
| Derryree Wood Management Limited | Households | 2007 |
| DHU Varren Land Management Ltd | Households | 2018 |
| Diagnostic Health Services Ltd | Extraterritorial | 1997 |
| Diamond Fireworks Ltd | Wholesale & retail | 2000 |
| Diamond Property PAL Limited | Real estate | 2024 |
| Diligent Tyre Ltd | Wholesale & retail | 2020 |
| Djlm Consultants Ltd | Real estate | 2012 |
| Djlm Properties Limited | Real estate | 2018 |
| Dkni Limited | Construction | 2016 |
| Doagh Equestrian Ltd | Agriculture & fishing | 2025 |
| Doagh Preschool Playgroup Limited | Education | 2025 |
| Doagh Village Green Development Ltd | Households | 2018 |
| Docker's GIN Company Ltd | Extraterritorial | 2019 |
| Doherty YEA Limited | Real estate | 2000 |
| Donegall Park Gardens Ltd | Households | 2018 |
| Dooish Meadows Management Company Ltd | Households | 2018 |
| Dorvic Caravans Ltd | Wholesale & retail | 2005 |
| Double Arrows Limited | Hospitality | 2022 |
| Douglas Hill Management Ltd | Households | 2016 |
| Dowellys Empire Ltd | Wholesale & retail | 2020 |
| Downpatrick & District Anglers Association Limited | Arts & recreation | 2014 |
| DR Ruth Maybin Radiology Ltd | Health & social care | 2024 |
| Drum Landscapes Limited | Administrative & support | 2020 |
| Drumack Wind Ltd | Energy | 2016 |
| Drumahoe Developments Limited | Extraterritorial | 2005 |
| Drumanaway Campers Ltd | Wholesale & retail | 2023 |
| Drumorgan Crescent Management Ltd | Extraterritorial | 2005 |
| DS Contracting Limited | Professional & scientific | 2008 |
| DSM Property Group Limited | Real estate | 2025 |
| DUA Ireland Ltd | Wholesale & retail | 2014 |
| Dual Plumbing and Building Services Ltd | Construction | 2019 |
| Dubeal Logistics Limited | Transport & logistics | 2013 |
| Ducpor Limited | Manufacturing | 2013 |
| Dunadry Gate Management Ltd | Households | 2021 |
| Dundee Property LLP | | 2007 |
| DW Mcneill & Sons Ltd | Transport & logistics | 2005 |
| DXN Design Ltd | Professional & scientific | 2021 |
| Dyna Finds Ltd | Wholesale & retail | 2025 |
| E.M.S (Ireland) Ltd | Information & communication | 2013 |
| Eagle Fellowship Trust | Other services | 2003 |
| Easi Holdings Ltd | Financial services | 2022 |