| Connect Car Lease Ltd | Administrative & support | 2024 |
| Connect Electrical Engineering Ltd | Construction | 2023 |
| Conor Ltd | Wholesale & retail | 2022 |
| Construction Junction Limited | Construction | 2012 |
| Consult CPK Ltd | Professional & scientific | 2022 |
| Consumer Rights CIC | Health & social care | 2021 |
| Convenience Extra Ltd | Wholesale & retail | 2014 |
| Conwell Developments Management Company Limited | Households | 2004 |
| Conzoltan Ltd | Health & social care | 2026 |
| COR Winds Ltd | Professional & scientific | 2024 |
| Core Consulting Business Growth Advisors Limited | Professional & scientific | 2014 |
| Core Growth Enterprises Limited | Financial services | 2020 |
| Cormac Developments Limited | Administrative & support | 2023 |
| Corner Pocket Bangor Sports Bar Ltd | Hospitality | 2024 |
| Corvus Detection Dogs Limited | Extraterritorial | 2020 |
| Corvus Security Limited | Administrative & support | 2008 |
| Cosimac Ltd | Manufacturing | 2021 |
| Cotswold Flats Limited | Extraterritorial | 1984 |
| Covato Limited | Information & communication | 2016 |
| Cove Bay Software Limited | Information & communication | 2003 |
| Cowey Holdings Ltd | Real estate | 2021 |
| CQ Contracts (N.I.) Limited | Construction | 2020 |
| Crabtree Contracts Ltd | Administrative & support | 2016 |
| Craig Counselling Ltd | Health & social care | 2026 |
| Craig YR Onnen Medical Ltd | Health & social care | 2025 |
| Craigboy Limited | Agriculture & fishing | 2021 |
| Craigdarragh Rise Management Ltd | Extraterritorial | 2024 |
| Craighill Developments Limited | Construction | 2018 |
| Craigtara Limited | Extraterritorial | 1992 |
| Crainia Ltd | Administrative & support | 2022 |
| Crawford & ZOU Ltd | Hospitality | 2013 |
| Crawford Commerce Limited | Professional & scientific | 2024 |
| Crawfords Farm Management Company Limited | Households | 2021 |
| Crawfordsburn Developments Ltd | Construction | 2019 |
| Crawfordsburn Meadows Management Co Ltd | Real estate | 2015 |
| Cread CYF | Information & communication | 2004 |
| Creating Chances Ltd | Health & social care | 2010 |
| Creative Commercial Interiors Limited | Other services | 2009 |
| Creative Faces NI Ltd | Arts & recreation | 2023 |
| Crestleaf Ltd | Wholesale & retail | 2025 |
| Crestmere Limited | Professional & scientific | 2005 |
| Criska Limited | Construction | 2018 |
| Cronfa Ymddeol RGH CYF. | Financial services | 2025 |
| Crown Kings Afro Barbers Ltd | Other services | 2025 |
| Crown Place Woking Limited | Construction | 2019 |
| Crowther Medical Imaging Limited | Health & social care | 2021 |
| Crumlin Estates 505 Limited | Households | 2023 |
| Cryan Holdings Limited | Financial services | 2021 |
| Crystalline Limited | Information & communication | 2001 |
| Crystallineworld Limited | Wholesale & retail | 2026 |
| CS Window Cleaning Limited | Administrative & support | 2025 |
| CSW Retrofit CYF. | Professional & scientific | 2025 |
| CUBIC3 Ltd | Real estate | 2010 |
| Culture Bakeries Ltd | Manufacturing | 2021 |
| Current Solutions Niuk Limited | Construction | 2025 |
| Curry Library Ltd | Hospitality | 2026 |
| Cursed Cards TCG Ltd | Wholesale & retail | 2025 |
| Customhouse Student Limited | Construction | 2015 |
| Cwmni Caban Gerlan CYF | Hospitality | 2002 |
| Cwmni Pendraw CYF | Arts & recreation | 2016 |
| Cwmni'R Fran WEN CYF | Arts & recreation | 1995 |
| Cyfeillion Cae'R Gors CYF | Arts & recreation | 1997 |
| Cyfieithu Acen Ltd | Professional & scientific | 2021 |
| Cylchog CYF. | Professional & scientific | 2021 |
| Cymdeithas Cyfieithwyr Cymru CYF. | Other services | 2003 |
| Cymdeithas Porwyr Aber a Llanfairfechan CYF | Administrative & support | 2006 |
| Cyngor AR Bopeth Gogledd Cymru North Wales Citizens Advice | Other services | 2023 |
| Cyreth Ltd | Hospitality | 2014 |
| Cyswllt CYF. | Construction | 2012 |
| Côpa Countryside Limited | Professional & scientific | 2022 |
| Côpa Pet Transport Limited | Transport & logistics | 2025 |
| D Chubb Limited | Transport & logistics | 2011 |
| D Hayes Solicitors Ltd | Professional & scientific | 2020 |
| D Mckay Automation Ltd | Manufacturing | 2024 |
| D West & Company Limited | Professional & scientific | 2023 |
| D&K Food Services Limited | Hospitality | 2010 |
| D-Plan Limited | Information & communication | 2017 |
| D. Hughes Welding & Fabrication Limited | Manufacturing | 2008 |
| D.N. Robinson Limited | Professional & scientific | 2004 |
| D.R. (Student) Limited | Construction | 2008 |
| DAC (Bangor) Cyfyngedig | Real estate | 2012 |
| DAD & Daughter Decorating Limited | Construction | 2022 |
| Daddy Promotions Ltd | Arts & recreation | 2010 |
| Dafydd Hardy Estate Agents Limited | Real estate | 1999 |
| Dafydd Hardy Trustee Limited | Professional & scientific | 2024 |
| Dajow Afromart Ltd | Wholesale & retail | 2025 |
| Dalby Avenue Bedminster Limited | Construction | 2021 |
| Daly Clean Carpet and Upholstery Cleaning Ltd | Administrative & support | 2025 |
| Daly Clean NI Ltd | Administrative & support | 2022 |
| Dalyan Properties Limited | Real estate | 2006 |
| Dameerza Limited | Wholesale & retail | 2025 |
| Danco Limited | Financial services | 2015 |
| Darley Student Accommodation Limited | Construction | 2013 |
| Darren Smith Martech Services Limited | Information & communication | 2023 |
| Data Based Medicine Global Limited | Information & communication | 2010 |
| Datacymru Ltd | Information & communication | 2008 |
| Davenport Specialist Printing Ltd | Manufacturing | 2014 |
| David Alexander Limited | Real estate | 1993 |
| David Jones Training Limited | Other services | 2009 |
| David Mawhinney & Sons Ltd | Wholesale & retail | 2014 |