| Connsbrook Avenue Apartments Ltd | Households | 2007 |
| Connswater Developments Ltd | Construction | 2018 |
| Connswater Graphics Limited | Manufacturing | 1985 |
| Connswater SC Limited | Real estate | 2021 |
| Connswater Specsavers Limited | Wholesale & retail | 2001 |
| Connswater Visionplus Limited | Wholesale & retail | 1999 |
| CONNSWATER24 Limited | Real estate | 2024 |
| Conomy Limited | Real estate | 2020 |
| Conor Carson Electrics Ltd | Information & communication | 2016 |
| Conor Crawford Ltd | Transport & logistics | 2021 |
| Conor Downey & Co Limited | Professional & scientific | 2011 |
| Conor Houston Associates Ltd | Professional & scientific | 2024 |
| Conor Mccann Engineering Ltd | Professional & scientific | 2025 |
| Conroy Financial Planning LLP | | 2018 |
| Consarc Design Group Limited | Professional & scientific | 1989 |
| Consarc Developments Limited | Professional & scientific | 2000 |
| Conscious Estate Ltd | Real estate | 2026 |
| Consequor Limited | Information & communication | 2014 |
| Consero Finance Limited | Financial services | 2015 |
| Consi Way Limited | Wholesale & retail | 2025 |
| Consistent Improvements Ltd | Wholesale & retail | 2024 |
| Consolidated Pumps (N.I.) Limited | Administrative & support | 1980 |
| Constantin Luxury Accommodation Ltd | Hospitality | 2025 |
| Constar Properties Limited | Real estate | 2016 |
| Constentum Ltd | Information & communication | 2018 |
| Construction Contracts Ltd | Construction | 2015 |
| Construction Employers Federation Limited | Other services | 1945 |
| Construction Industry Accountants Ltd | Professional & scientific | 2025 |
| Construction Industry Consultants Ltd | Professional & scientific | 2025 |
| Construction Industry Futures Limited | Construction | 1945 |
| Construction Labour & Plant Ltd | Construction | 2024 |
| Construction Manage Ltd | Construction | 2023 |
| Construction Measure Ltd | Professional & scientific | 2019 |
| Construction Register Limited | Professional & scientific | 1998 |
| Construction Towards Next Generation Limited | Real estate | 2007 |
| Consult HS (NI) Ltd | | 2004 |
| Consult NB1 Limited | Administrative & support | 2004 |
| Consultants ME Group Ltd | Professional & scientific | 2017 |
| CONSULTS3 Ltd | Information & communication | 2020 |
| Consumer Code for Online Dispute Resolution Ltd. | Information & communication | 2019 |
| Contac Claims Limited | Financial services | 2008 |
| Contacq Ltd | Information & communication | 2001 |
| Contemporary Christianity (Northern Ireland) Limited | Other services | 1999 |
| Content Management Service Ltd | Information & communication | 2020 |
| Continental Apartments NI Limited | Hospitality | 2018 |
| Continental Teves UK Limited | Wholesale & retail | 2025 |
| Continually Limited | Information & communication | 2018 |
| Contract Ceilings Limited | Extraterritorial | 2012 |
| Contractcarsni.Com Ltd | Wholesale & retail | 2014 |
| Contracting Management Development Ltd | Construction | 2016 |
| Contracts (NI) Ltd | Construction | 2014 |
| Contrast (IRL) Limited | Health & social care | 2025 |
| Controlsoft Automation Systems (NI) Limited | Manufacturing | 2024 |
| Contstar Organization L.P. | | 2018 |
| Convenza Ltd | Professional & scientific | 2018 |
| Converged Entertainment Limited | Information & communication | 2022 |
| Conversations Productions Limited | Administrative & support | 2020 |
| Convery MS Ltd | Administrative & support | 2005 |
| Convery Properties Limited | Real estate | 2024 |
| Conveyortek Limited | Manufacturing | 2009 |
| Convis Limited | Real estate | 1998 |
| Conway Care Holdings Limited | Health & social care | 2026 |
| Conway Care Homes Limited | Health & social care | 2026 |
| Conway Consultancy Limited | Information & communication | 2016 |
| Conway Education Centre Limited | Education | 1995 |
| Conway Mill Preservation Trust Limited | Real estate | 1999 |
| Conway Todd & Co Solicitors Limited | Professional & scientific | 2017 |
| Conwell Civil Engineering Limited | Wholesale & retail | 2015 |
| Cooberpedy Ltd | Financial services | 2020 |
| Coobet Trading Ltd | Hospitality | 2020 |
| Coogan & Co. Architects Limited | Professional & scientific | 1999 |
| Cookdnn Ltd | Information & communication | 2024 |
| Cooke & Kettyle LLP | | 2008 |
| Cookflow Ireland Ltd | Transport & logistics | 2022 |
| Cookstown GP Practice C.I.C. | Health & social care | 2023 |
| Cool Data Centres Ltd | Information & communication | 2017 |
| Cool DC Technologies Ltd | Extraterritorial | 2017 |
| Cool Kidz Ltd | Education | 2026 |
| Cool YUM Limited | Wholesale & retail | 2024 |
| Cooleborough Limited | Real estate | 2017 |
| Cooley's Ltd | Wholesale & retail | 2001 |
| Cooleys Holdings Limited | Wholesale & retail | 2019 |
| Coolhaven Developments Ltd | Construction | 1976 |
| Coolmar Ballymena Ltd | Wholesale & retail | 2026 |
| Coomealla Catering Limited | Hospitality | 2016 |
| Coomealla Hospitality Ltd | Hospitality | 2012 |
| Cooper & Anglin Limited | Health & social care | 1990 |
| Cooper Innovation Trding Ltd | Wholesale & retail | 2024 |
| Coopers (N.I.) Ltd. | Hospitality | 1994 |
| Coopers Mill NO. 1 Management Company Limited | Households | 2009 |
| Coopers Mill NO.2 Management Company Limited | Households | 2011 |
| Coopers Mill NO.3 Management Company Limited | Households | 2015 |
| Coora Ltd | Administrative & support | 2017 |
| Cooshty Limited | Real estate | 2020 |
| Copacetic Business Solutions Ltd | Professional & scientific | 2018 |
| Coparr Properties Limited | Real estate | 2018 |
| Copia Eleven Ltd | Real estate | 2026 |
| Copius Advisory Services LLP | | 2009 |
| Coppi Fine Foods Ltd | Hospitality | 2017 |
| Coppi Restaurants Limited | Hospitality | 2011 |