| Cosysolar Limited | Construction | 2023 |
| Cottage Farm Seaforde Limited | Agriculture & fishing | 2019 |
| County Down Rural Community Network | Other services | 2002 |
| CPG Media Limited | Information & communication | 2009 |
| CPS Ward Construction Ltd | Construction | 2006 |
| Crebisol Limited | Administrative & support | 2017 |
| Credo Civil Engineering Ltd | Construction | 2019 |
| Crescent Heritage Apartments Ltd | Construction | 2025 |
| Crilly Holdings Ltd | Households | 2025 |
| Crockstar Limited | Arts & recreation | 2010 |
| Crossgar Commercials Ltd | Wholesale & retail | 2015 |
| Crossgar Estates Ltd | Construction | 2016 |
| Crossgar Food Co Ltd | Wholesale & retail | 2020 |
| Crossgar Garage Services Ltd | Wholesale & retail | 2015 |
| Crossgar WAR Memorial Community Hall Committee | Arts & recreation | 2012 |
| Crytensoft Limited | Information & communication | 2018 |
| Cultúrlann Leath Chathail Ltd | Education | 2026 |
| Curve Craft Limited | Manufacturing | 2009 |
| CZM Limited | Professional & scientific | 2024 |
| D&Cl Family Investment Company | Financial services | 2025 |
| D&Ebs Limited | Real estate | 2024 |
| D&S Quality Joinery Ltd | Construction | 2011 |
| D.Hamill Auto Repairs Limited | Manufacturing | 2025 |
| DAN Long Associates Ltd | Professional & scientific | 2007 |
| David Gilmore & Co Ltd | Professional & scientific | 2005 |
| Dccg Ltd | Wholesale & retail | 2023 |
| Deborah Jean Loveday Ltd | Real estate | 2018 |
| Derryboye Films Ltd | Information & communication | 2018 |
| Design & Development Interiors Ltd | Construction | 2008 |
| Dfend Cloud Solutions Limited | Information & communication | 2023 |
| Dfpm Management Ltd | Professional & scientific | 2022 |
| DGW Cable Services Ltd | Construction | 2024 |
| Digital Curve Ltd | Wholesale & retail | 2023 |
| Digital Scanning Services Ltd | Information & communication | 2013 |
| Dino Pizza Limited | Hospitality | 2025 |
| Direwolf Events Limited | Administrative & support | 2017 |
| DJA Building Works Ltd | Construction | 2020 |
| DK Bricklaying Ltd | Construction | 2025 |
| DMA Films Ltd | Information & communication | 2018 |
| DOC Elite Ltd | Information & communication | 2018 |
| Doing and Learning Ltd | Information & communication | 2021 |
| Dolly's Farm Ltd | Agriculture & fishing | 2020 |
| Donard View Farms Ltd | Agriculture & fishing | 2011 |
| Dootdoot Music Ltd | Administrative & support | 2016 |
| Down Community Arts | Arts & recreation | 1993 |
| Down Community Radio Limited | Information & communication | 2009 |
| Down District Accessible Transport | Transport & logistics | 2000 |
| Down Electrical Services Ltd | Construction | 2019 |
| Down Hydraulics Ltd | Other services | 2019 |
| Down Property Care (GMN) Limited | Water & waste | 2024 |
| Down Property Care Ltd | Water & waste | 2005 |
| Down Rigging Ltd | Professional & scientific | 2023 |
| Down Surgical Ltd | Wholesale & retail | 2003 |
| Down Tyres Limited | Wholesale & retail | 2014 |
| Downe Dental Care Ltd | Health & social care | 2007 |
| Downe Travel Service Limited | Administrative & support | 1982 |
| Downpatrick and County Down Railway Society Limited | Transport & logistics | 1985 |
| Downpatrick Construction Ltd | Construction | 2013 |
| Downpatrick Property Trust Limited | Construction | 1993 |
| Downpatrick Race Club | Arts & recreation | 1949 |
| Downpatrick Specsavers Limited | Wholesale & retail | 2016 |
| DPH Civils & Sports Grounds Limited | Arts & recreation | 2025 |
| DPH Construction Ltd | Construction | 1997 |
| DPH Plumbing & Heating Ltd | Construction | 2025 |
| DPK Developments (NI) Ltd | Construction | 2014 |
| DPK Nails Limited | Other services | 2025 |
| DR Carissa Ltd | Health & social care | 2023 |
| Dragonfly Adventures Ltd | Education | 2025 |
| Drop Hopper Ltd | Manufacturing | 2015 |
| Drop Lock Leave Ltd | Real estate | 2013 |
| Drpk Contracts Limited | Construction | 2012 |
| Drumcloon Limited | Hospitality | 2022 |
| Drumroe Consulting Ltd | Administrative & support | 2015 |
| DS Caravan Services Ltd | Professional & scientific | 2023 |
| DS Mcgrath Car Sales Ltd | Wholesale & retail | 2019 |
| DSC Cars Ltd | Wholesale & retail | 2009 |
| Dufferin Apartments Ltd | Households | 2011 |
| Dundrum Bay Crab Products Limited | Wholesale & retail | 2018 |
| Dunmorris Ltd | Real estate | 2025 |
| Dunnanelly Consulting LLP | | 2023 |
| East Coast Fuel Stop Ltd | Wholesale & retail | 2019 |
| East Down Hire Ltd | Administrative & support | 2013 |
| East Down Limited | Extraterritorial | 2021 |
| East Essence 2026 Ltd | Hospitality | 2026 |
| Ecojustice Ireland Community Interest Company | Professional & scientific | 2021 |
| Ecojustice Legal Action Centre Limited | Professional & scientific | 2021 |
| Ecoplastic Recycling Ltd | Manufacturing | 2005 |
| Edgewater Holiday Park Ltd | Hospitality | 2017 |
| Edifice Investments Ltd | Real estate | 2019 |
| Edward J Magee Limited | Construction | 2014 |
| Eibhear Ltd | Extraterritorial | 2014 |
| EJS International Ltd | Wholesale & retail | 2025 |
| Eleador Limited | Wholesale & retail | 2017 |
| Electric Vehicle Converter Limited | Manufacturing | 2019 |
| Elevate VA N.I. Ltd | Administrative & support | 2026 |
| Elite Engineering Crossgar Ltd | Manufacturing | 2025 |
| Elite Medical Training Services Ltd | Administrative & support | 2004 |
| Elliott's Place Management Company Ltd | Households | 2023 |
| Emana Group Ltd | Information & communication | 2019 |
| Emantee Ltd | Hospitality | 2026 |