| City Tanning Limited | Other services | 2025 |
| City to City Belfast Ltd | Other services | 2024 |
| City Trust and Corporate Services (N.I.) Limited | Administrative & support | 2007 |
| City Vape Ltd | Wholesale & retail | 2022 |
| City Vets Ltd | Professional & scientific | 2011 |
| City Wellness and Sports Medicine (N.I.) Ltd | Health & social care | 2018 |
| Citybull Limited | Wholesale & retail | 2024 |
| Citybus Limited | Transport & logistics | 1972 |
| Cityflex Ltd | Information & communication | 2025 |
| Citygate Insurance Services Limited | Financial services | 2007 |
| Citypost NI Ltd | Transport & logistics | 2018 |
| Citysleeps Limited | Real estate | 2025 |
| Citywide Group Holdings Limited | Financial services | 2024 |
| Citywide Propery Solutions Ltd | Real estate | 2025 |
| Citywide Wealth Ltd | Financial services | 2015 |
| Civcol Limited | Construction | 2014 |
| Civenta Ltd | Information & communication | 2026 |
| Civet Developments Limited | Real estate | 1997 |
| Civica NI Limited | Information & communication | 2002 |
| Civil Engineering Services & Supplies Limited | Construction | 1997 |
| CJ Collins Auto Electrics Ltd | Wholesale & retail | 2025 |
| CJ Mullan ML Limited | Health & social care | 2023 |
| CJ NI Consultancy Ltd | Information & communication | 2025 |
| CJB Academy Limited | Other services | 2024 |
| Cjb's Surf Company (NI) Limited | Wholesale & retail | 2025 |
| CJC Consultant Solutions Ltd | Information & communication | 2018 |
| CJC Mechanical Limited | Professional & scientific | 2025 |
| CJC Occupational Health & Wellbeing Limited | Health & social care | 2019 |
| CJE Propco Ltd | Real estate | 2025 |
| CJF Properties Ltd | Real estate | 2026 |
| CJF Property Investments Ltd | Real estate | 2024 |
| CJG Holdings NI Ltd | Financial services | 2024 |
| Cjhd Engineering Ltd | Manufacturing | 2024 |
| CJJ (N.I.) Ltd | Hospitality | 2019 |
| CJM Electrical(Ni) Ltd | Construction | 2021 |
| Cjma Limited | Wholesale & retail | 2017 |
| Cjmediamarketing Ltd | Professional & scientific | 2023 |
| Cjmkkl Limited | Wholesale & retail | 2024 |
| CJP Group Limited | Professional & scientific | 2019 |
| CJP Professional Services Ltd | Information & communication | 2016 |
| CJR and Sons Ltd | Wholesale & retail | 2018 |
| Cjrh Ltd | Wholesale & retail | 2020 |
| CJS Cars Ltd | Wholesale & retail | 2014 |
| CJS Payroll Limited | Professional & scientific | 1998 |
| Cjsg Solutions Ltd | Information & communication | 2019 |
| CJT Plumbing & Heating Limited | Construction | 2021 |
| CKB Electrical Limited | Manufacturing | 2023 |
| Ckbp Ltd | Real estate | 2021 |
| Ckec Products Ltd | Financial services | 2026 |
| CKJ Cars N.I. Ltd | Wholesale & retail | 2024 |
| CKJ Orthopaedics Limited | Health & social care | 2023 |
| CKN Supplies Ltd | Wholesale & retail | 2011 |
| CKQ Cleaning Professionals Ltd | Administrative & support | 2025 |
| Ckrt Contracts Ltd | Administrative & support | 2026 |
| CL Botanicals Limited | Manufacturing | 2021 |
| CL Merchant Services Ltd | Administrative & support | 2025 |
| Clacked Studio Ltd | Manufacturing | 2025 |
| Clad FIX Contracts (2016) Ltd | Construction | 2016 |
| Clada Actuarial Solutions Ltd | Professional & scientific | 2024 |
| Cladagh Limited | Financial services | 2012 |
| Claddagh Choice Ltd | Wholesale & retail | 2025 |
| Claddagh Trading Ltd | Wholesale & retail | 2024 |
| Cladding Xperts Ltd | Wholesale & retail | 2022 |
| Claim Consultants Direct Ltd | Financial services | 2020 |
| Claim Reaction Adjusting Ltd | Financial services | 2013 |
| Claim Xtra Ltd | Financial services | 2021 |
| Claims Assist Technical Services Ltd | Administrative & support | 2010 |
| Claims TEC Limited | Financial services | 2019 |
| Claire Baxter Ltd | Arts & recreation | 2013 |
| Claire Boylan Ltd | Health & social care | 2013 |
| Claire Condron ND Ltd | Health & social care | 2025 |
| Claire Mccaffrey Limited | Administrative & support | 2020 |
| Claire Mcstravick Ltd | Professional & scientific | 2024 |
| Claire O'Sullivan Coaching Limited | Other services | 2021 |
| Claire Preston Consultancy Limited | Professional & scientific | 2024 |
| Claire Reynolds Ltd | Professional & scientific | 2023 |
| Clan Events Ltd | Arts & recreation | 2024 |
| Clan MOR Surestart | Health & social care | 2003 |
| Clanaboy Lane Management Company Ltd | Households | 2025 |
| Clandeboye Court Management Limited | Households | 2026 |
| Clandeboye Investments Limited | Financial services | 2012 |
| Clandeboye Management Co. Ltd | Real estate | 2022 |
| Clanmil Developments Limited | Construction | 2012 |
| Clanmil Properties Limited | Other services | 1999 |
| Clann Bhreasail Eire Limited | Professional & scientific | 2022 |
| Clanroy Limited | Hospitality | 1987 |
| Clanua Limited | Wholesale & retail | 1999 |
| Clara James Homes Limited | Real estate | 2024 |
| Clara Leeson Ltd | Professional & scientific | 2017 |
| Clare Veterinary Practice Limited | Extraterritorial | 2011 |
| Claremont House Limited | Households | 2017 |
| Clarence Kennedy Ltd | Professional & scientific | 2022 |
| Clarendon (NI) Limited | Administrative & support | 1999 |
| Clarendon Cars (Belfast) Limited | Wholesale & retail | 2025 |
| Clarendon Development Association Ltd | Arts & recreation | 2022 |
| Clarendon Executive Limited | Professional & scientific | 2013 |
| Clarendon Ifni Equity CI LP | | 2023 |
| Clarendon Silos Limited | Extraterritorial | 1997 |
| Clarified Development Ltd | Information & communication | 2024 |
| Clarisse Cosmetics Limited | Wholesale & retail | 2025 |