| Carnvalley Construction Ltd | Construction | 2018 |
| Carolan Property Management Limited | Households | 2016 |
| Carolhill Properties Ltd | Real estate | 2025 |
| Caroline Girvan Fitness Ltd | Extraterritorial | 2022 |
| Caroline Hill Ltd | Information & communication | 2018 |
| Carpet Pro Belfast Ltd | Administrative & support | 2023 |
| Carpetworld (N.I.) Limited | Wholesale & retail | 1985 |
| Carpetworld Saintfield Road (NI) Ltd | Wholesale & retail | 2015 |
| Carramac Plant Hire Ltd | Construction | 2026 |
| Carrick Electrix Limited | Construction | 2021 |
| Carrick Hire Centre Ltd | Extraterritorial | 2021 |
| Carrick Little Properties Limited | Other services | 2020 |
| Carrick Rangers (Holding) Limited | Extraterritorial | 2016 |
| Carrick Rangers Community Partnership Limited | Other services | 2025 |
| Carrick Rangers Football Club Limited | Arts & recreation | 2000 |
| Carrick Rangers Global Academy Limited | Arts & recreation | 2024 |
| Carrick Wellness Ltd | Health & social care | 2013 |
| Carrickfergus Chemists Limited | Wholesale & retail | 1976 |
| Carrickhill Investments Limited | Financial services | 2016 |
| Carrigagh Limited | Hospitality | 2007 |
| Carrigart Stores Ltd | Wholesale & retail | 2023 |
| Carrik Care Ltd. | Health & social care | 2015 |
| Carrowdore Solar Limited | Energy | 2014 |
| Carruthers Electrical Ltd | Construction | 2024 |
| Carryduff Auto Parts Limited | Wholesale & retail | 2006 |
| Carryduff Baptist Corporation Limited | Health & social care | 1986 |
| Carryduff Boarding Kennels Ltd | Other services | 2013 |
| Carryduff Building Supplies Limited | Manufacturing | 2006 |
| Carryduff Construction Company Limited | | 1973 |
| Carryduff Forklift Limited | Wholesale & retail | 1991 |
| Carryduff Hardware Ltd | Wholesale & retail | 2017 |
| Carryduff OIL Supplies Ltd | Transport & logistics | 2019 |
| Carryduff Storage Limited | Transport & logistics | 2024 |
| Carryduff Tyre Centre Limited | Administrative & support | 2001 |
| Carryhappy Limited | Wholesale & retail | 2025 |
| Carsena Energy Holdco Ltd | Energy | 2024 |
| Carsena Investments Ltd | Financial services | 2019 |
| Carsmartni Ltd | Wholesale & retail | 2024 |
| Carson Builders N.I Ltd | Extraterritorial | 2019 |
| Carson Catering (N.I.) Limited | Hospitality | 2024 |
| Carson Mcdowell LLP | | 2012 |
| Cartech Auto Mechanical NI Ltd | Wholesale & retail | 2026 |
| Carterl Limited | Wholesale & retail | 2025 |
| Cartw Connect Trading Ltd | Wholesale & retail | 2024 |
| Cartwheel Maritime Limited | Wholesale & retail | 2020 |
| Carty Johnson Limited | Professional & scientific | 2006 |
| Carwood Management Company Limited | Extraterritorial | 2000 |
| CAS Restaurants Limited | Hospitality | 2013 |
| Casa Ltd | Real estate | 2019 |
| Casa Tomara Ltd | Manufacturing | 2011 |
| Casa Vacanze GE Ltd | Wholesale & retail | 2025 |
| Casaba Security Ltd | Information & communication | 2022 |
| Casajot Ltd | Real estate | 2012 |
| Casalane Limited | Real estate | 2014 |
| Casam Marine Consultants Ltd | Professional & scientific | 2025 |
| Cascade Legacy Ltd | Agriculture & fishing | 2024 |
| Cased Dimensions Ltd | Information & communication | 2009 |
| Casement Court Management Company Ltd | Real estate | 2007 |
| Casement Group Ltd | Professional & scientific | 2021 |
| Casement Manor Apartment Management Company Limited | Administrative & support | 2005 |
| Casey Car and Commercial Ltd | Financial services | 2024 |
| Casey Corporate Support Ltd. | Professional & scientific | 2014 |
| Cash MB Ltd | Health & social care | 2024 |
| Cashel Quarries Limited | Extraterritorial | 2008 |
| Cashelton Manor Limited | Households | 2016 |
| Cashflow Management Ltd | Administrative & support | 1983 |
| Casia Catering Limited | Transport & logistics | 2022 |
| Caskey Medical Services Limited | Health & social care | 2023 |
| Caslin Commerce Ltd | Wholesale & retail | 2026 |
| Cass Engineering Services Ltd | Manufacturing | 2018 |
| Cassidy Geotechnical Ltd | Professional & scientific | 2015 |
| Cassidy Lighting Ltd | Professional & scientific | 2026 |
| Cassidy Properties Ltd | Real estate | 2003 |
| Cast Iron Baths Ireland Limited | Wholesale & retail | 2021 |
| Cast Iron Radiators Ireland Limited | Wholesale & retail | 2021 |
| Cast Planning Ltd | Information & communication | 2023 |
| Casta Limited | Real estate | 2025 |
| Castle Buildings Management Limited | Real estate | 2022 |
| Castle Clouds Ltd | Wholesale & retail | 2025 |
| Castle Community Trust | Education | 2015 |
| Castle Compliance Electrical Services Ltd | Administrative & support | 2025 |
| Castle Court (Tandragee) Limited | Extraterritorial | 2006 |
| Castle Court Investments Limited | | 1994 |
| Castle Distribution Ltd | Wholesale & retail | 2013 |
| Castle Eden Consultancy Limited | Professional & scientific | 2026 |
| Castle Enterprise 2017 Limited | Hospitality | 2017 |
| Castle Glen Development Company Limited | Financial services | 1997 |
| Castle Hill 2024 Ltd | Hospitality | 2024 |
| Castle Lane NI Developments Limited | Construction | 2023 |
| Castle Locksmiths Limited | Wholesale & retail | 2012 |
| Castle Mall Traders Limited | Real estate | 2021 |
| Castle North West Limited | Real estate | 2015 |
| Castle Pharma Holdings Ltd | Financial services | 2024 |
| Castle Pharmacy Limited | Wholesale & retail | 2005 |
| Castle Place Developments Limited | Real estate | 2022 |
| Castle Publican Limited | Hospitality | 2013 |
| Castle Seaview Developments Limited | Construction | 2017 |
| Castle View Close (Dundrum) Management Company Limited | Real estate | 2014 |
| Castle Youth Theatre Company Ltd | Education | 2025 |
| Castleabbey Properties Limited | Real estate | 1982 |