| Ceramics Architectural Limited | Construction | 2017 |
| Cerc Ltd | Hospitality | 2024 |
| Cerrig a Cartref CYF | Construction | 2021 |
| Chambers Industries Ltd | Wholesale & retail | 2022 |
| Chambers Legacy Solutions Ltd | Financial services | 2025 |
| Chambers Motors Limited | Wholesale & retail | 2025 |
| Chaplin Gate Management Company Limited | Households | 2002 |
| Charcam Properties Limited | Construction | 2026 |
| Chatsworth Procurement Solutions Ltd. | Professional & scientific | 2016 |
| Cheah Rothe Architects Ltd | Professional & scientific | 2016 |
| Chef GB Events Limited | Hospitality | 2018 |
| Chester Developments (NI) Limited | Construction | 2003 |
| Chester Park Inns Limited | Hospitality | 2000 |
| Children's Early Intervention Trust | Education | 2006 |
| Childsplay N. Ireland Ltd | Other services | 1975 |
| China City Bangor Limited | Hospitality | 2024 |
| Chippy Potato Ltd | Hospitality | 2023 |
| CHL Talent Limited | Professional & scientific | 2017 |
| Chloco Limited | Other services | 2015 |
| Chop Chop Asian Kitchen Ltd | Hospitality | 2025 |
| Choux Choux Limited | Hospitality | 2010 |
| Chris Griffiths Limited | Construction | 2019 |
| Christchurch Road Bournemouth Limited | Construction | 2014 |
| Christian Kane Fishing Ltd | Agriculture & fishing | 2018 |
| Christian Phipps & Co Limited | Professional & scientific | 2019 |
| Chronotrack UK Limited | Other services | 2009 |
| Church Court Property Management Limited | Extraterritorial | 2021 |
| Church Lane Court Donaghadee Apartments Limited | Households | 1999 |
| CI Fashion Ltd | Wholesale & retail | 2025 |
| Cicero AI Ltd | Information & communication | 2023 |
| Cimotatech Limited | Information & communication | 2021 |
| Circumspect Safety Solutions Ltd | Professional & scientific | 2025 |
| City Express Mechanic Limited | Wholesale & retail | 2025 |
| City Mini Ltd | Wholesale & retail | 2025 |
| CJ Software Consulting Ltd | Information & communication | 2026 |
| Cj.Christie Ltd | Hospitality | 2025 |
| CK Waimai Limited | Manufacturing | 2022 |
| CKT (NI) Ltd | Households | 2025 |
| Ckwm Trading Limited | Wholesale & retail | 2026 |
| Clandeboye Consulting Limited | Professional & scientific | 2017 |
| Clandeboye Dental Healthcare Ltd | Health & social care | 2023 |
| Clandeboye Estate Company Limited-The | Agriculture & fishing | 1950 |
| Clandeboye Yoghurt Ltd | Manufacturing | 2019 |
| Clarity Diagnostics Limited | Health & social care | 2024 |
| Clarksan Developments Ltd | Real estate | 2015 |
| Classic Marque Limited | Construction | 1994 |
| Classic Sailboats Ltd | Manufacturing | 2003 |
| Claus Neubauer Ltd | Wholesale & retail | 2023 |
| Claymore Courier Logistics Ltd | Transport & logistics | 2025 |
| Clean Wave Software Limited | Information & communication | 2019 |
| Cleanfields Technologies Ltd | Professional & scientific | 2008 |
| Clearly Aquatics Ltd | Agriculture & fishing | 2011 |
| Cleaver Stewart Ltd | Professional & scientific | 2003 |
| Clifdene Apartments Limited | Extraterritorial | 1996 |
| Clifton Developments NI Ltd | Construction | 2007 |
| Climate Craic CIC | Other services | 2022 |
| Clinton NEL Properties Limited | Real estate | 2021 |
| Clinton Retail Ltd | Wholesale & retail | 2022 |
| Close Focus Limited | Professional & scientific | 2015 |
| Cloudbase Productions Limited | Professional & scientific | 2017 |
| CLUB24FITNESS Belfast Ltd | Arts & recreation | 2026 |
| CLUB24FITNESS Ltd | Arts & recreation | 2021 |
| Clwb Rygbi Bethesda CYF | Arts & recreation | 2016 |
| Co'Couture Limited | Manufacturing | 2008 |
| Coach & Develop Ltd | Administrative & support | 2007 |
| Coach Hill Motors Ltd | Wholesale & retail | 2003 |
| Coached by Carbs Ltd | Education | 2025 |
| Coal & Diamond Limited | Health & social care | 2012 |
| Coast DRY Cleaners Limited | Wholesale & retail | 2013 |
| Coast View Cottages Management Limited | Extraterritorial | 2003 |
| Coastline Electrical Ltd | Construction | 2019 |
| Coates Engineering Limited | Manufacturing | 2015 |
| Coco Operative Community Interest Company | Professional & scientific | 2020 |
| Cocon Construction Limited | Administrative & support | 1978 |
| Cocon Developments Limited | Extraterritorial | 1984 |
| Cocon Limited | Professional & scientific | 1998 |
| Coed Natur CYF. | Agriculture & fishing | 2024 |
| Coetir Mynydd | Agriculture & fishing | 2003 |
| Coffee and Adventures Ltd | Hospitality | 2025 |
| Cofnod - North Wales Environmental Information Service Limited | Information & communication | 2005 |
| Colin Bradley Contracts Ltd | Construction | 2021 |
| Colin Fitzpatrick Consulting Limited | Professional & scientific | 2023 |
| Collings Quay Limited | Real estate | 2016 |
| Collins Mechanical and Electrical Ltd | Construction | 2024 |
| Comber Distillery Apartment Ltd | Extraterritorial | 2004 |
| Comber Distillery Management Ltd | Extraterritorial | 2004 |
| Combined Properties Limited | Construction | 2010 |
| Commercial and Industrial Battery Services Limited | Professional & scientific | 2021 |
| Commercial Kitchen Specialists Limited | Manufacturing | 2011 |
| Communications Solutions Ireland Limited | Information & communication | 2024 |
| Community Advice Ards and North Down Ltd | Other services | 1998 |
| Company Talk Ltd | Education | 2005 |
| Comparative Insight Limited | Information & communication | 2025 |
| Compass Support Services CIC | Administrative & support | 2025 |
| Complete Estates Ltd | Construction | 2025 |
| Complete Plumbing Solutions UK Limited | Construction | 2022 |
| Complete Pools and Leisure Ltd | Water & waste | 2018 |
| Component-Shop.Co.Uk Ltd | Wholesale & retail | 2005 |
| Computer MOT Centre Limited | Wholesale & retail | 2005 |
| Conington Road Lewisham Limited | Construction | 2020 |