| CM Connect Ltd | Extraterritorial | 2025 |
| Cmac Sports Limited | Manufacturing | 2018 |
| CMC Contracts Ltd | Construction | 2026 |
| CMC Plant Hire Limited | Wholesale & retail | 2020 |
| Cmmp Limited | Information & communication | 2020 |
| CMP Livestock Ltd | Wholesale & retail | 2025 |
| CMS Construction (Armagh) Limited | Construction | 2018 |
| Coached Fitness Coaching & Education Ltd | Other services | 2025 |
| Coaching Systems Ltd | Information & communication | 2026 |
| Cobrena Ltd | Hospitality | 2022 |
| Cocolane Beauty Spa Limited | Other services | 2021 |
| Cocolane Nail Salon Limited | Other services | 2021 |
| Coffee Cart (Cartin's Mill) Limited | Hospitality | 2024 |
| Cold Logic Ltd | Transport & logistics | 2015 |
| Coldharbour Lane Ltd | Construction | 2014 |
| Colettes.Garage Ltd | Information & communication | 2025 |
| Colin Donnelly Transport Ltd | Transport & logistics | 2014 |
| Collone Properties Limited | Administrative & support | 2018 |
| Combilift N.I. Limited | Manufacturing | 2025 |
| Combra Limited | Construction | 1995 |
| Commercial Services (Armagh) Limited | Manufacturing | 2011 |
| Commercial Trailers Limited | Wholesale & retail | 2019 |
| Complete Cleaning Solutions Ireland Ltd | Administrative & support | 2024 |
| Complete Kitchen Services Armagh Ltd | Construction | 2022 |
| Complieye Ltd | Real estate | 2024 |
| Concept Smyth Healthcare Limited | Health & social care | 2024 |
| Conchobhar Limited | Construction | 2015 |
| Concrete Wetcast Machinery Ltd | Manufacturing | 2023 |
| Concur Consultancy Ltd | Professional & scientific | 2018 |
| Congo Initiative UK | Other services | 2018 |
| Conleth Duffy Contracts Ltd | Construction | 2016 |
| Connectni Ltd | Administrative & support | 2025 |
| Connolly Haulage Limited | Transport & logistics | 2017 |
| Conor Duffy Construction Ltd | Construction | 2014 |
| Construction Cost Consultants Limited | Construction | 2015 |
| Construe Ltd | Administrative & support | 2010 |
| Conway Farm Produce Ltd | Agriculture & fishing | 2020 |
| Conway Services Ltd | Wholesale & retail | 2019 |
| Conway Signs & Graphics Ltd | Other services | 2015 |
| Cookstown Polymers Limited | Wholesale & retail | 2024 |
| Cool Fuel Efficient Nutrition Ltd | Wholesale & retail | 2018 |
| Cooltemp Refrigeration Limited | Professional & scientific | 2011 |
| COR Validation Ltd | Professional & scientific | 2025 |
| Corhammock Ltd | Financial services | 2011 |
| Corlen Limited | Real estate | 2010 |
| Corliss Mill Construction Ltd | Construction | 2021 |
| Cormac Leonard Commercials Ltd | Wholesale & retail | 1991 |
| Cormeen Social and Economic Regeneration Partnership Ltd | Other services | 2018 |
| Cornacassa Holdings Ltd | Real estate | 2022 |
| Cornascriebe Consultants Limited | Information & communication | 1996 |
| Cornerstone Contractors Ltd | Construction | 2020 |
| Corporation Property Ltd | Real estate | 2025 |
| Corr Brothers Ltd | Wholesale & retail | 2011 |
| Corr Group Ltd | Financial services | 2017 |
| Corr Security Systems Ltd | Administrative & support | 2020 |
| Corran Holdings Limited | Financial services | 2022 |
| Corrigan Construction Ltd | Construction | 2019 |
| Corrinare Properties Limited | Real estate | 2026 |
| Corvan Chartered Accountants Ltd | Professional & scientific | 2019 |
| Costello Vehicle Logistics (UK) Limited | Transport & logistics | 2020 |
| Country Decking Ltd | Construction | 2026 |
| Country Gent Ltd | Wholesale & retail | 2018 |
| Countryside Management Training Ltd | Professional & scientific | 2024 |
| Countryside Motors NI Limited | Wholesale & retail | 2018 |
| County Armagh Grand Orange Lodge Community Development Committee Limited | Arts & recreation | 2005 |
| County Armagh Phoenix Group Limited | Other services | 2014 |
| Course Way Limited | Administrative & support | 2024 |
| COX Distribution Limited | Transport & logistics | 2017 |
| Coyle Fabrications Ltd | Manufacturing | 2016 |
| CP O'Neill Electrical Limited | Construction | 2017 |
| CPD Powerline Ltd | Energy | 2005 |
| CPS Commercials Limited | Real estate | 2005 |
| CPS Residential Ltd | Real estate | 2026 |
| Craigavon Pest Control Ltd | Administrative & support | 2025 |
| Creative Fitout Ltd | Construction | 2019 |
| Creenagh Energy Limited | Energy | 2014 |
| Creggan Farm and Garden Limited | Wholesale & retail | 2022 |
| Crest Software Solutions Limited | Information & communication | 2026 |
| Crewe Nurseries Limited | Wholesale & retail | 2003 |
| Cross Refrigeration (N.I.) Limited | Construction | 1983 |
| Crosscut Ltd | Construction | 2023 |
| Crossfire South Armagh Ltd | Other services | 2025 |
| Crosskeys Flooring & Groundworks Limited | Construction | 2021 |
| Crossmaglen Dismantlers Ltd | Water & waste | 2026 |
| Crossmore Hospitality Limited | Real estate | 2012 |
| Crossmore Property Holdings Ltd | Real estate | 2019 |
| Crosstrees Arboriculture Limited | Administrative & support | 2020 |
| Crozier Computers Ltd | Wholesale & retail | 2023 |
| Cruisingpackages Limited | Administrative & support | 2015 |
| Cruz Deliveries Ltd | Transport & logistics | 2015 |
| CS Business Services Consultancy Limited | Professional & scientific | 2024 |
| CSS Land Surveys Ltd | Professional & scientific | 2005 |
| CT Utilities Ltd | Construction | 2020 |
| CTB Developments Limited | Real estate | 2017 |
| CTB Retail | Wholesale & retail | 2013 |
| Cullen Contracts Ltd | Agriculture & fishing | 2004 |
| CUP 'N Cone Ltd | Wholesale & retail | 2019 |
| Curran Contracts Armagh Ltd | Construction | 2021 |
| Curran Contracts Ltd | Construction | 2005 |
| Curran Sports Grounds Ltd | Administrative & support | 2021 |