| CMC Crane and Wind Consultancy Ltd | Professional & scientific | 2025 |
| CMC Properties NI Ltd | Real estate | 2024 |
| CMK Properties Limited | Construction | 2024 |
| CML Quality Consulting Ltd | Information & communication | 2026 |
| CMS Parts Limited | Wholesale & retail | 2026 |
| Coach Lane Developments Limited | Real estate | 2010 |
| Coach Lane Properties Limited | Real estate | 2010 |
| Coach Solutions Ltd | Wholesale & retail | 2021 |
| Cobbers Ltd | Real estate | 2024 |
| Cobra Media Ltd | Professional & scientific | 2017 |
| Cobra Specialist Security Services Ltd | Other services | 1998 |
| Coby Developments Holdco Limited | Financial services | 2024 |
| Cockhill Contracts Ltd | Real estate | 2026 |
| Codfather Hot Food Ltd - the | Hospitality | 2003 |
| Cognate Engineering Ltd | Professional & scientific | 2024 |
| Cohen & Co. Events Ltd | Administrative & support | 2024 |
| Cohen & Co. Interiors Ltd | Wholesale & retail | 2021 |
| Colidar Project LP | | 2015 |
| Colin Boyes Limited | Construction | 2014 |
| Colon Health Ltd | Health & social care | 2021 |
| Colortec (Belfast) Ltd | Wholesale & retail | 2008 |
| Colt Developments N.I Ltd | Construction | 2024 |
| Columbus Management Services Limited | Professional & scientific | 2017 |
| Columbus Professional Consultancy Limited | Professional & scientific | 2020 |
| Comfoud Limited | Wholesale & retail | 2025 |
| Comfy Belfast Stays Ltd | Real estate | 2021 |
| Comfy NI Stays Ltd | Real estate | 2024 |
| Commentary Corner Ltd | Information & communication | 2025 |
| Commercial Heating Specialists Ltd | Manufacturing | 2015 |
| Common Wellbeing and Mental Health CIC | Health & social care | 2018 |
| Community Advice Lisburn & Castlereagh | Other services | 2006 |
| Compass Refurbs Ltd | Construction | 2019 |
| Complete Fleet Solutions Ltd | Wholesale & retail | 2023 |
| Complete Mortgage Solutions NI Ltd | Financial services | 2007 |
| Compliapp Limited | Administrative & support | 2019 |
| Conn & Fenton Limited | Other services | 2022 |
| Connected Business Limited | Information & communication | 2017 |
| Consolidated Merchandisers (N.I.) Limited | Transport & logistics | 1998 |
| Contract Tile & Stone (NI) Ltd | Construction | 2013 |
| Conwal Properties Limited | Real estate | 2020 |
| Cookie Coach Co. Ltd | Wholesale & retail | 2011 |
| Coolkeeragh BES Ltd | Energy | 2021 |
| Coolmix Limited | Wholesale & retail | 2023 |
| Coppelia Holdings Limited | Financial services | 2019 |
| Cornerstone (NI) Ltd | Construction | 2014 |
| Cornerstone Construction (NI) Ltd | Construction | 2014 |
| Cornerstone SPV Ltd | Financial services | 2019 |
| Corravan Ltd | Real estate | 2022 |
| Cosy Dens Limited | Real estate | 2025 |
| Cottage Dessert Products Ltd | Manufacturing | 2016 |
| Cottage Desserts Ltd | Manufacturing | 2024 |
| Coulter Homes Limited | Construction | 1983 |
| Country Agri Limited | Agriculture & fishing | 2013 |
| Country Kitchen Home Bakery Limited | Manufacturing | 2017 |
| Countryside Developments (N.I.) Limited | Construction | 2019 |
| Cove Asset and Advisory Ltd | Real estate | 2024 |
| Coyle Agencies Ltd | Wholesale & retail | 2003 |
| Cpil (NI) NO. 1 Limited | Real estate | 2023 |
| Crafted Saunas UK Ltd | Wholesale & retail | 2025 |
| Craigferm Ltd | Agriculture & fishing | 2020 |
| Craighill Heights Management Limited | Households | 2025 |
| Cranberry Market LP | | 2019 |
| Cranslough Properties Limited | Real estate | 2022 |
| Creative Composites Limited | Manufacturing | 2000 |
| Creative Corporate Holdings Limited | Financial services | 2023 |
| Creative Financial Investors Limited | Professional & scientific | 2023 |
| Creative Properties & Investments (NI) Limited | Financial services | 2023 |
| Creatively Sustainable Ltd | Wholesale & retail | 2022 |
| Creevy Properties LLP | | 2022 |
| Crescent Blow DRY Bar Limited | Other services | 2011 |
| Crescent Business Park Ltd | Real estate | 2004 |
| Crescent Capital III Founder Partner Limited | Professional & scientific | 2011 |
| Crescent Capital III GP Limited | Professional & scientific | 2011 |
| Crescent Capital III LP | | 2011 |
| Crescent Nominees Limited | Professional & scientific | 2014 |
| Crestview Technologies Limited | Manufacturing | 2020 |
| Crisscross Removals Limited | Households | 2019 |
| Crockard ASC Limited | Manufacturing | 2015 |
| Cross Family Group Holdings Limited | Financial services | 2015 |
| Cross FT Limited | Financial services | 2022 |
| Cross Lane Enterprise Park Ltd | Real estate | 2021 |
| Crossey's Garage Ltd | Wholesale & retail | 2022 |
| Crown Castle UK Limited | | 1999 |
| Crown Hill Enterprises Limited | Wholesale & retail | 2018 |
| Crownpro Asset Resources Limited | Professional & scientific | 2025 |
| Crucial Metal Ltd | Manufacturing | 2020 |
| Cruckaclady Mountain Limited | Energy | 2015 |
| CSC Property Management Limited | Real estate | 2018 |
| CSK Estate Ltd | Real estate | 2025 |
| Cskickz Limited | Wholesale & retail | 2024 |
| Csmc Limited | Real estate | 2013 |
| CSR (NI) Limited | Administrative & support | 2008 |
| CTS Fire and Security Ltd | Administrative & support | 2026 |
| Cuan Properties Limited | Real estate | 2025 |
| Cuddles Day Nursery (NI) Limited | Health & social care | 2006 |
| Cullen Contracts and Hire Ltd | Construction | 2025 |
| Cullen Hire Limited | Administrative & support | 2011 |
| Cullenary Cuisine Ltd | Hospitality | 2025 |
| Cullion Hydrogen Services Ltd | Construction | 2022 |
| Cullion Wind Farm II Limited | Energy | 2023 |