| Clarity Consulting Limited | Professional & scientific | 2025 |
| Clarity Recruitment Ventures (UK) Limited | Administrative & support | 2016 |
| Clarity Telecom Limited | Information & communication | 2000 |
| Clarive AI Ltd | Information & communication | 2026 |
| Clarke and Whiteman Ltd | Professional & scientific | 2014 |
| Clarke Automotive Ltd | Wholesale & retail | 2026 |
| Clarke Connections Ltd | Real estate | 2025 |
| Clarke Construction Enterprises Ltd | Professional & scientific | 2022 |
| Clarke Cunningham Tree Maintenance Limited | Other services | 1999 |
| Clarke Dunlop Consultants Limited | Professional & scientific | 2019 |
| Clarke Holdings(Ni) Ltd | Real estate | 2015 |
| Clarke Housing Group Ltd | Construction | 2016 |
| Clarke Stewart Limited | Wholesale & retail | 2022 |
| Clarke Stone Direct Ltd | Manufacturing | 2025 |
| Clarke&Co NI Accountants Ltd | Professional & scientific | 2020 |
| Clarksville Limited | Financial services | 2014 |
| Clarman Limited | Professional & scientific | 2005 |
| Clarman Partnership Limited | Professional & scientific | 2015 |
| Claro Skin Clinic Limited | Health & social care | 2014 |
| Clas Holdings Ltd | Real estate | 2017 |
| Class Acts Promotions (Ireland) Ltd | Extraterritorial | 1997 |
| Class Consultancy Services Limited | Professional & scientific | 2001 |
| Classic Curry House Ltd | Hospitality | 2026 |
| Classic Haircut Dealers Limited | Other services | 2023 |
| Classic Mineral Water Company Limited | Manufacturing | 1976 |
| Classic Motor Services Limited | Wholesale & retail | 2024 |
| Classic Sports & Travel Options LLP | | 2005 |
| Classical Enterprises Limited | Administrative & support | 1997 |
| Claudia Loren'T Limited | Wholesale & retail | 2025 |
| Clavey Consulting Limited | Professional & scientific | 2018 |
| Clay Incorporated Ltd | Extraterritorial | 2019 |
| Claysco Limited | Extraterritorial | 2025 |
| CLC Hospitality Systems Ltd | Wholesale & retail | 2026 |
| Cldz Consulting Limited | Information & communication | 2023 |
| Clean CUT Cuisine Ltd | Hospitality | 2017 |
| Clean Grid NI Ltd | Manufacturing | 2025 |
| Clean Slate Television Limited | Information & communication | 2003 |
| Cleanaway Limited | | 1981 |
| Cleaner Holmes Ltd | Administrative & support | 2026 |
| Cleaner PAL Ltd | Administrative & support | 2024 |
| Cleaning Drains Jetting Limited | Construction | 2025 |
| Cleanworks Services Limited | Administrative & support | 2015 |
| Clear Consulting Solutions Limited | Information & communication | 2005 |
| Clear Customs Agents Ltd | Transport & logistics | 2021 |
| Clear Day Nurseries | Health & social care | 2005 |
| Clear Dental Care (Expedia) Limited | Health & social care | 2019 |
| Clear Dental Care (Lurgan) Limited | Extraterritorial | 2013 |
| Clear Dental Care (NI) Limited | Health & social care | 2011 |
| Clear Eyes Trading Ltd | Wholesale & retail | 2025 |
| Clear Flower Limited | Wholesale & retail | 2023 |
| Clear Healthcare | Wholesale & retail | 2005 |
| Clear Healthcare (Belfast) Limited | Professional & scientific | 2016 |
| Clear Healthcare (Forres) Limited | Wholesale & retail | 2018 |
| Clear Homes | Real estate | 2005 |
| Clear Invest Limited | Real estate | 2014 |
| Clear Landmark | Extraterritorial | 2013 |
| Clear Pharma Limited | Extraterritorial | 2012 |
| Clear Pharmacy | Wholesale & retail | 2005 |
| Clear Property (Lisburn Road) Limited | Real estate | 2019 |
| Clear Property South Limited | Extraterritorial | 2013 |
| Clear Rosemount Limited | Real estate | 2011 |
| Clear Sky Facilities Management Limited | Real estate | 2014 |
| Clear Training Academy Limited | Education | 2025 |
| Clear Value | Extraterritorial | 2000 |
| Clear Vision INT. Limited | Wholesale & retail | 2022 |
| Clear Water Systems Limited | Professional & scientific | 2024 |
| Clearbox Communications Ltd | Professional & scientific | 2014 |
| Clearbox Group Holdings Ltd | Financial services | 2025 |
| Clearly Kids Limited | Education | 2015 |
| Clearpath Finance Limited | Financial services | 2016 |
| Clearwater Cleaning Ltd | Administrative & support | 2023 |
| Cleaver (N.I.) Ltd | Hospitality | 2023 |
| Cleaver Avenue Limited | Construction | 2021 |
| Cleaver Court Limited | Extraterritorial | 1987 |
| Cleaver Fulton Rankin Trustees Limited | Extraterritorial | 2012 |
| Cleeve Racing Limited | Arts & recreation | 2011 |
| Clelandrenwick Ltd | Professional & scientific | 2023 |
| Clemens Zick Ltd | Wholesale & retail | 2024 |
| Clerical Medical Unit Trust Managers Limited | | 1986 |
| Clever COW Limited | Education | 2020 |
| Cleverbutton LLP | | 2023 |
| Click Nexa Ltd | Wholesale & retail | 2026 |
| Clickclick Video Marketing Ltd | Information & communication | 2024 |
| Clickmodus Limited | Information & communication | 2026 |
| Clicksavvy Ltd | Wholesale & retail | 2023 |
| Client 33 Ltd | Other services | 2024 |
| Client Analysis and Relationship Development (Card) Limited | Professional & scientific | 2004 |
| Clientcapture Ltd | Information & communication | 2026 |
| Clifden Associates Limited | Professional & scientific | 2025 |
| Clifford Mcmullan & Co Limited | Wholesale & retail | 1926 |
| Clifton Development Management (NI) Limited | Construction | 2022 |
| Clifton Gate Property Management Company Limited | Extraterritorial | 2005 |
| Clifton House Centre Limited | Arts & recreation | 2010 |
| Clifton Properties N.I. Ltd | Construction | 2026 |
| Cliftonville Enterprises | Education | 2017 |
| Cliftonville Football Development Centre Community Partnership | Construction | 2015 |
| Cliftonville G S Ltd | Wholesale & retail | 2023 |
| Cliftonville Golf Club, Limited | Arts & recreation | 1922 |
| Cliftonville Healthcare Limited | Health & social care | 2010 |
| Cliftonville Stores Ltd | Wholesale & retail | 2020 |