| Carnrig Holdings Limited | Financial services | 2025 |
| Carriff Ltd | Information & communication | 2023 |
| Castle Home Trends Limited | Wholesale & retail | 2020 |
| Castlehill Farm Management Company Limited | Households | 2001 |
| Cat Distributions Ltd | Wholesale & retail | 2026 |
| Catalyst BLU Limited | Professional & scientific | 2019 |
| CB Services Limited | Extraterritorial | 2017 |
| CBP Health Ltd | Health & social care | 2021 |
| Cbpt Commerce Ltd | Wholesale & retail | 2025 |
| CCH Property Management Ltd | Hospitality | 2024 |
| CD Digital Ltd | Professional & scientific | 2024 |
| CDE (NI) Ltd | Construction | 2012 |
| Central Belfast Apartments Ltd | Hospitality | 2016 |
| Central Belfast Contact Centre | Health & social care | 2000 |
| Central Fire Protection (NI) Ltd | Manufacturing | 2013 |
| CG 2028 Ltd | Hospitality | 2025 |
| CG Service (N. Ireland) Ltd | Manufacturing | 2010 |
| CGL (Ravenhill) Ltd | Real estate | 2021 |
| CGL 1 Ltd | Construction | 2020 |
| Chainbridge Steel (NI) Limited | Wholesale & retail | 2016 |
| Chaintax Limited | Information & communication | 2026 |
| Chapter Xiii Community Interest Company | Wholesale & retail | 2021 |
| Cheerful Ltd | Information & communication | 2022 |
| Chef Innovation Ltd | Hospitality | 2017 |
| Chef KIN Glengormley Ltd | Hospitality | 2024 |
| Cherryvale Furniture Warehouse Limited | Wholesale & retail | 2023 |
| Chester Homes Ltd | Health & social care | 1987 |
| Chezpurcellthedoghotel Ltd | Other services | 2021 |
| Chirayil Associates Limited | Health & social care | 2023 |
| Christine Gregg Dental Care Limited | Health & social care | 2016 |
| Chrysalis Beauty Ltd | Other services | 2007 |
| Chrysalis Hair and Beauty Ltd | Other services | 2008 |
| Ciara Magill-Lavery Ltd | Administrative & support | 2023 |
| Ciccone Park Ltd | Real estate | 2024 |
| Circa 89 Ltd | Professional & scientific | 2018 |
| City Mechanical Services, Limited | | 1946 |
| City Podiatry Ltd | Health & social care | 2024 |
| Civicode Ltd | Information & communication | 2023 |
| CJH Aviation Ltd | Manufacturing | 2021 |
| CJK Property Investment Ltd | Real estate | 2017 |
| CJM Fire & Security Ltd | Other services | 2024 |
| CJT Transport Limited | Transport & logistics | 2016 |
| CL2R Holdings Limited | Financial services | 2017 |
| Claire Hammond Interiors Limited | Professional & scientific | 2011 |
| Clark the Spark Ltd | Construction | 2023 |
| Classic Carpets and Beds (N.I.) Limited | Wholesale & retail | 2022 |
| Cleancare Ireland Ltd | Wholesale & retail | 2014 |
| Cleaninggemni Ltd | Administrative & support | 2025 |
| Cleankingni Ltd | Construction | 2024 |
| Cleanxpressni Ltd | Administrative & support | 2023 |
| Clear Financial Mortgage Services Limited | Other services | 2008 |
| Clear Skies Pest Management Ltd | Administrative & support | 2026 |
| Clearco Cleaning NI Ltd | Administrative & support | 2022 |
| Clearco Cleaning Services Ltd | Administrative & support | 2015 |
| Clonaslea Property Developments Ltd | Real estate | 2026 |
| Club Gymnasia Limited | Arts & recreation | 2014 |
| CLÓ NUA Limited | Manufacturing | 2026 |
| CMD Holdings Ltd | Wholesale & retail | 2023 |
| Cmmedical Ltd | Health & social care | 2021 |
| Coast Connection Property Ltd | Real estate | 2024 |
| Coco Group Holdings Limited | Financial services | 2025 |
| Cocobros Chocolate Ltd | Manufacturing | 2022 |
| Cogoot Ltd | Administrative & support | 2019 |
| Colette Skelton Hair Design & Education Ltd | Extraterritorial | 2016 |
| Colin Graham Lettings Ltd | Real estate | 2022 |
| Collaborate (UK) Limited | Professional & scientific | 2014 |
| Collinward Wholesale Limited | Extraterritorial | 1985 |
| COM 2026 Limited | Financial services | 2022 |
| Comfort Furniture Ltd | Wholesale & retail | 2024 |
| Commercial Motor Products Ltd | Wholesale & retail | 1990 |
| Community Relations Forum Ltd. | Health & social care | 2011 |
| Complete GAS Services Belfast Ltd | Construction | 2020 |
| Component Distributors (Holdings) Limited | Extraterritorial | 1985 |
| Component Distributors Group Limited | Extraterritorial | 2008 |
| Component Distributors Limited | Wholesale & retail | 1963 |
| Computer Maintenance Ireland Limited | | 1994 |
| Confetti & Co. 7 LLP | | 2025 |
| Construction Equipment Distribution Limited | Wholesale & retail | 2012 |
| Construction Supervisory Services Ltd | Professional & scientific | 2001 |
| Coole Fusion Ltd | Manufacturing | 2021 |
| Coole Fusion Rathcoole Ltd | Hospitality | 2024 |
| Coolewell Trading Ltd | Professional & scientific | 2024 |
| Copeland Bird Observatory | Professional & scientific | 2025 |
| Copius (NI) Ltd | Professional & scientific | 2008 |
| Corby Rock Consultants Ltd | Professional & scientific | 2023 |
| Core Domain Ltd | Information & communication | 2016 |
| Core Impact Ltd | Professional & scientific | 2017 |
| COREY800 Ltd | Extraterritorial | 2023 |
| Corick Investments Limited | Construction | 1990 |
| Cortexcart Limited | Information & communication | 2025 |
| Coruscent Proprietas Ltd | Real estate | 2024 |
| Cosy Corner Cafe Whitewell Ltd | Hospitality | 2025 |
| Cotswold Gardens Management Company Limited | Real estate | 2013 |
| Cottonmount Holdings Ltd | Financial services | 2019 |
| Countryside Coaches Ltd | Transport & logistics | 2024 |
| Countrywide Freight (Midlands) Limited | Transport & logistics | 1983 |
| Countrywide Freight (Northern Ireland) Limited | Transport & logistics | 1991 |
| Countrywide Freight (Northern) Limited | Transport & logistics | 1979 |
| Countrywide Freight (Southern) Limited | Transport & logistics | 1978 |
| Countrywide Freight London Limited | Transport & logistics | 2007 |