| Cake in a TIN Limited | Manufacturing | 2020 |
| Caledonian Freight Ireland Ltd | Transport & logistics | 2024 |
| Calibro Workspace Limited | Manufacturing | 2015 |
| California Superstars Ltd | Information & communication | 2022 |
| CAM Holdings MG Limited | Financial services | 2021 |
| Camden Holdco Limited | Financial services | 2026 |
| Camden Properties NO.1 Limited | Real estate | 2026 |
| Campbe Limited | Wholesale & retail | 2025 |
| Carcon Insulation Specialists Ltd | Construction | 2026 |
| Cardiodata Advisory Ltd | Information & communication | 2026 |
| Carer House Limited | Information & communication | 2018 |
| Carnbeg House Property Management Company Limited | Real estate | 2010 |
| Carndale Management Limited | Real estate | 2005 |
| Carrig-Na-Cule Management Services Company Limited | Extraterritorial | 2003 |
| Cartlyle Ltd | Health & social care | 2022 |
| Castle Homes Timber Frame Limited | Construction | 2023 |
| Castleberg Systems L.P. | | 2017 |
| Castlehill Contracts Limited | Construction | 2014 |
| Catering Equipment Engineers Limited | Administrative & support | 1980 |
| Causeway Waste Limited | Water & waste | 2021 |
| Celloexpress Limited | Wholesale & retail | 2017 |
| Central Tanker Services Ltd | Manufacturing | 2009 |
| Centum Engineering Services Ltd | Construction | 2015 |
| CGP Extraction Systems (2016) Ltd | Manufacturing | 2016 |
| Chaperone Solutions Ltd | Health & social care | 2019 |
| Charidon Limited | Health & social care | 2023 |
| Charlie Keenan Country Wear & Outdoor Clothing (Toome) Ltd | Wholesale & retail | 2009 |
| Cherukara Dental Ltd | Health & social care | 2013 |
| Christian Corp Limited | Health & social care | 2023 |
| Church Road Enterprises Limited | Construction | 2017 |
| Cimc Vehicles UK Limited | Financial services | 2016 |
| Circadian Locations Ltd | Arts & recreation | 2023 |
| CJM Commerce Ltd | Wholesale & retail | 2024 |
| CL Aviation Ltd | Manufacturing | 2021 |
| Clady Group Ltd | Financial services | 2021 |
| Clandeboye Agencies Ltd | Wholesale & retail | 2013 |
| Claria Collective Ltd | Real estate | 2026 |
| Clearcon Cookorr Ltd | Real estate | 2024 |
| Clearcon Holdings Ltd | Financial services | 2021 |
| Clearcon Jory Ltd | Financial services | 2025 |
| Clearcon Magowan West Ltd | Real estate | 2022 |
| Clearcon Pro Ltd | Real estate | 2021 |
| Cler Services Limited | Extraterritorial | 2010 |
| Cloverleafcare Group Ltd | Health & social care | 2025 |
| CM Plastering Contracts Ltd | Construction | 2016 |
| CM Skips (Coleraine) Limited | Water & waste | 2021 |
| Cmass Ltd | Information & communication | 2010 |
| CMC Finance Ltd | Financial services | 2024 |
| CMC Procurement Services Ltd | Health & social care | 2026 |
| Cocobongobingo Ltd | Arts & recreation | 2021 |
| COD Electrics Ltd | Construction | 2023 |
| Coffee Logistics Ireland Limited | Wholesale & retail | 2013 |
| Coformni Limited | Extraterritorial | 2023 |
| Colin Graham Residential Ltd | Real estate | 2016 |
| Communicon Ltd | Information & communication | 2020 |
| Compliance Engineering International Ltd | Professional & scientific | 2020 |
| Compliance Engineering Ltd | Hospitality | 1988 |
| Comucare Ltd | Health & social care | 2019 |
| Connaught Wind Limited | Energy | 2010 |
| Connect Construction Management Ltd | Construction | 2021 |
| Connect the Dots IT Ltd | Information & communication | 2018 |
| Contact Marketing (NI) Limited | Wholesale & retail | 2003 |
| Controls Automation Electrical Services Limited | Construction | 2015 |
| Conway & Lough Ltd | Professional & scientific | 2026 |
| Coogan Plastering Limited | Construction | 2019 |
| Corr Limited | Energy | 2015 |
| Corrigan CA Limited | Professional & scientific | 2011 |
| Cotters Park Ltd. | Hospitality | 2023 |
| Cotton Electrical Controls Limited | Manufacturing | 2004 |
| Cova Tradings Ltd | Hospitality | 2025 |
| Cpjk Consulting Limited | Professional & scientific | 2015 |
| CPM (2022) Ltd | Construction | 2022 |
| Crab Management Limited | Extraterritorial | 2024 |
| Cracked Limited | Extraterritorial | 2024 |
| Craig Dixon Consulting Limited | Professional & scientific | 2016 |
| Craigstown Roofing & Cladding Limited | Construction | 2002 |
| Crane Financial Services Ltd | Financial services | 2020 |
| Cranfield Groundworks and Plant Hire Ltd | Construction | 2025 |
| Cranky Sparrow Automotive Limited | Wholesale & retail | 2017 |
| Creagh Concrete Products Limited | Mining & quarrying | 1975 |
| Creamy Vintage Limited | Wholesale & retail | 2026 |
| Credimus Technologies Ltd | Professional & scientific | 2023 |
| Creeve Properties Ltd | Real estate | 2018 |
| Creevx Limited | Administrative & support | 2018 |
| Crevenagh Properties Limited | Construction | 2016 |
| CRM Courier Services Ltd | Transport & logistics | 2019 |
| Crossfit Wolfhound Larne Ltd | Arts & recreation | 2024 |
| Cscottinternational Ltd | Transport & logistics | 2018 |
| CSI Thermo Ltd | Transport & logistics | 2025 |
| CT2R Solutions Ltd | Professional & scientific | 2015 |
| Cubo Solutions Ltd | Information & communication | 2004 |
| Culnafay Limited | Real estate | 2013 |
| Custom Bike Club (NI) Ltd | Other services | 2018 |
| CW Energy Services Limited | Wholesale & retail | 2024 |
| CWC (NI) Ltd | Water & waste | 2012 |
| Cybersyd Ltd | Professional & scientific | 2022 |
| Cygjbflcgs Limited | Wholesale & retail | 2025 |
| D & C Farming Limited | Agriculture & fishing | 2025 |
| D&G Air Conditioning Ltd | Energy | 2013 |
| D.L Access Ltd | Construction | 2019 |