| Causeway Voluntary Action Trust | Health & social care | 1996 |
| Causewaysoft Ltd | Information & communication | 2020 |
| Cbin Developments Limited | Construction | 2025 |
| Cbin Limited | Construction | 2011 |
| Cbms Limited | Administrative & support | 2026 |
| CCH Productions Ltd | Arts & recreation | 2022 |
| CDM Systems Ltd | Information & communication | 2005 |
| Cece's Cakes and Bakes Limited | Wholesale & retail | 2022 |
| Cedars Property Management Limited | Households | 2005 |
| Celi Aesthetics Ltd | Other services | 2023 |
| Central Safety Solutions Ltd | Financial services | 2019 |
| CEO Performance & Rehab Ltd | Arts & recreation | 2024 |
| Chapel Lane Farm Limited | Construction | 2006 |
| Chapel View Property Management Company Ltd | Households | 2007 |
| Charles Court Management Services Company Limited | Real estate | 2006 |
| Charlie Property Ltd | Construction | 2018 |
| Chic Ltd | Real estate | 1996 |
| Chieftain Fleet Management Limited | Administrative & support | 2014 |
| Chill Foodhall Limited | Wholesale & retail | 2014 |
| Chique Sport Limited | Wholesale & retail | 2017 |
| Choice Sliding Wardrobes Limited | Manufacturing | 2019 |
| Chrisfit Ltd | Arts & recreation | 2018 |
| Christ the Redeemer International Ministries North Coast & Derry/Londonderry Ltd | Other services | 2024 |
| Christhealth Medicals Ltd | Health & social care | 2024 |
| Church View Heights Management Ltd | Households | 2019 |
| Cinchortho Ltd | Manufacturing | 2024 |
| CIRCUL8 Limited | Water & waste | 2018 |
| CJC Housing Ltd | Real estate | 2024 |
| CJO Holdings Ltd | Construction | 2020 |
| CK GEO Consulting UK Ltd | Professional & scientific | 2026 |
| CK Joinery Ltd | Construction | 2020 |
| CKZ Green Energy Ltd | Energy | 2015 |
| Claina Commercial Repairs Ltd | Wholesale & retail | 2018 |
| Clare Hill Management Limited | Households | 2020 |
| Clark & Sons Electrical Contractors Ltd | Construction | 2016 |
| Clarke Financial Planning Ltd | Financial services | 2013 |
| Classic Conservatories (NI) Limited | Construction | 2022 |
| Classic Lighting Limited | Construction | 2016 |
| Clean on the Coast Ltd | Administrative & support | 2024 |
| Cloisters Priestland Road Management Limited - the | Households | 2009 |
| Cloonavin Green Management Limited | Households | 2001 |
| Closed Systems Monitoring Limited | Professional & scientific | 2021 |
| Clover Lane Management Company Limited | Households | 2022 |
| Coach Hall Limited | Extraterritorial | 2017 |
| Coastal Getaways Articlave Ltd | Construction | 2022 |
| Coastal Horizon Castlerock Ltd | Hospitality | 2025 |
| Coastal Self Drive Ltd | Administrative & support | 2004 |
| Coastal Shield Ltd | Administrative & support | 2023 |
| Cochrane Dental Care Ltd | Health & social care | 2016 |
| Cogan & Shackleton LLP | | 2016 |
| Coleraine & District Samaritans | Other services | 2017 |
| Coleraine and District Motor Club Limited | Arts & recreation | 1964 |
| Coleraine Anglers Association Limited | Arts & recreation | 2013 |
| Coleraine BID | Other services | 2016 |
| Coleraine Football Club Limited | Arts & recreation | 2005 |
| Coleraine Glass Limited | Construction | 2022 |
| Coleraine Grammar Hockey C.I.C. | Arts & recreation | 2024 |
| Coleraine Grammar Rugby Association Ltd | Arts & recreation | 2024 |
| Coleraine Grammar School | Education | 2014 |
| Coleraine Nails & Spa Limited | Other services | 2024 |
| Coleraine Old Boys Rowing Association - the | Arts & recreation | 2003 |
| Coleraine Road Portstewart Land Management Ltd | Households | 2002 |
| Coleraine Rural & Urban Network | Administrative & support | 2010 |
| Coleraine Specsavers Hearcare Limited | Wholesale & retail | 2009 |
| Coleraine Specsavers Limited | Wholesale & retail | 1999 |
| Coleraine Street Pastors | Education | 2018 |
| Coleraine Sure Start Partnership | Education | 2002 |
| Coleraine Visionplus Limited | Wholesale & retail | 1999 |
| College Mews (Ballymena) Management Company Limited | Households | 2021 |
| Colum Mcauley (Builders) Ltd | Construction | 1999 |
| Community Advice Causeway | Other services | 1998 |
| Community Rescue Service Limited | Administrative & support | 2015 |
| Community Wellbeing NI C.I.C. | Wholesale & retail | 2023 |
| Composite Armourtech Ltd | Extraterritorial | 2011 |
| Conficius Ltd | Information & communication | 2022 |
| Connexus International Limited | Administrative & support | 2023 |
| Conra Properties Limited | Real estate | 2006 |
| Contract Caterers Ltd | Hospitality | 2025 |
| Contractors Insurance Guarantee Services (NI) Limited | Financial services | 1987 |
| Conway Property Development Limited | Construction | 2008 |
| Cooley Property NI Ltd | Households | 2025 |
| Coolna Bathrooms & Tiles Ltd | Construction | 2024 |
| Coolreaghs Manor Management Ltd | Households | 2020 |
| Copdoc Limited | Health & social care | 2010 |
| Coral Moon Productions Ltd | Information & communication | 2024 |
| Core Gym N.I. Limited | Arts & recreation | 2014 |
| Corrigan Henry Construction Limited | Construction | 2010 |
| Costello's Catering Ltd | Hospitality | 2023 |
| Count US in Ltd | Wholesale & retail | 2026 |
| Country Boys Ltd | Other services | 2020 |
| Courthall Management Limited | Extraterritorial | 2007 |
| Courtyard Land Management Ltd - the | Extraterritorial | 2004 |
| Covehill Development Management Limited | Households | 2000 |
| Covtek Rentals Ltd | Administrative & support | 2012 |
| Covtek Restaurants Ltd | Hospitality | 2017 |
| Coyle Court Management (NI) Ltd | Households | 2013 |
| CPG Restorative Services Ltd | Health & social care | 2023 |
| Craigaview Management Company Limited | Households | 2008 |
| Craigmore Farms Ltd | Agriculture & fishing | 2012 |
| Craigmore Management Limited | Transport & logistics | 2012 |