| Castlebann Ltd | Construction | 2025 |
| Castlebawn Holdings Ltd | Real estate | 2025 |
| Castlebawn Newtownards Ltd | Real estate | 2016 |
| Castlebloom Limited | Construction | 2018 |
| Castlebrook Furniture & Design (UK) Ltd | Construction | 2015 |
| Castlecourt Nails & Spa Ltd | Other services | 2024 |
| Castlecove Studios Ltd | Information & communication | 2026 |
| Castlehill Developments Ltd | Construction | 2025 |
| Castlehill Immigration Services Limited | Professional & scientific | 2020 |
| Castlehill Place Management Limited | Households | 2003 |
| Castlehill Wood Management Company Limited | Households | 2018 |
| Castlelea Properties Ltd | Construction | 2003 |
| Castlenahinch Limited | Construction | 2018 |
| Castlerainey Wind Ltd | Energy | 2016 |
| Castlereagh Apartments Ltd | Hospitality | 2020 |
| Castlereagh Cleaners Ltd | Administrative & support | 2022 |
| Castlereagh Homes Limited | Construction | 2018 |
| Castlereagh Investments Limited | Extraterritorial | 2005 |
| Castlereagh Ltd | Construction | 2020 |
| Castlereagh Motors Limited | Wholesale & retail | 1981 |
| Castlereagh Office Management Limited | Other services | 2004 |
| Castlereagh Plaza Limited | Hospitality | 2022 |
| Castlereagh Properties Limited | Financial services | 2003 |
| Castlereagh SUB Aqua Club | Arts & recreation | 2002 |
| Castlerock Trading Ltd | Wholesale & retail | 2012 |
| Castlerocklands Management Limited | Households | 2000 |
| Castleroe Developments Limited | Construction | 2025 |
| Castlesaint LLP | | 2021 |
| Castleshane Investments Limited | Financial services | 2018 |
| Castleton Court (Belfast) Management Company Ltd | Households | 2023 |
| Castleton Estates Limited | Real estate | 1991 |
| Castleton Mews Management Company Limited | Real estate | 2011 |
| Castleton Obgyn Limited | Health & social care | 2011 |
| Castleview Apartments (NI) Limited | Real estate | 2013 |
| Castleview Holdings (N.I.) Ltd | Financial services | 2020 |
| Castlewellan Education Ltd | Education | 2020 |
| Castlewood Court Management Ltd | Extraterritorial | 2009 |
| Castlewood Manor Apartments Limited | Extraterritorial | 1999 |
| Casual Time Limited | Wholesale & retail | 2024 |
| Caswell Business LP | | 2015 |
| Cat Jemmy Nutrition & Fitness Limited | Other services | 2024 |
| Cat Mert Ltd | Wholesale & retail | 2024 |
| Catagen Green Emissions Testing Limited | Professional & scientific | 2024 |
| Catalyst Arts Ltd | Arts & recreation | 1994 |
| Catalystpay Limited | Information & communication | 2019 |
| Catch 202 Ltd | Hospitality | 2019 |
| Catch a Blink Trading Ltd | Wholesale & retail | 2025 |
| Catch a Grip Limited | Administrative & support | 2022 |
| Cateraid Group Ltd | Professional & scientific | 2026 |
| Catering (NI) Ltd | Hospitality | 2014 |
| Catering Equipment Services Ltd | Wholesale & retail | 2016 |
| Catering Island Ltd | Hospitality | 2026 |
| Caterwell Restaurants Ltd | Hospitality | 1998 |
| Cathal GM Limited | Hospitality | 2016 |
| Cathand Enterprises Ltd | Real estate | 2021 |
| Cathedral Aesthetics Limited | Health & social care | 2023 |
| Cathedral Contracts Investments Ltd | Real estate | 2025 |
| Cathedral Contracts Ltd | Construction | 2020 |
| Cathedral EYE Clinic Limited | Health & social care | 2009 |
| Cathedral EYE Holdings Ltd | Financial services | 2021 |
| Cathedral EYE Research Foundation | Health & social care | 2012 |
| Cathedral Graphics Ltd | Manufacturing | 2009 |
| Cathedral Leisure Limited | Hospitality | 2013 |
| Cathedral Print Ltd | Manufacturing | 2023 |
| Cathedral Quarter Arts Festival | Arts & recreation | 2000 |
| Cathedral Quarter Trust | Education | 2012 |
| Cathedral View Management Company Limited | Extraterritorial | 2007 |
| Catherine Ewings Consulting Limited | Information & communication | 2021 |
| Catherine Fetherston Travel Counsellors Ltd | Administrative & support | 2026 |
| Catherine Peck Ltd | Wholesale & retail | 2021 |
| Catherine Phillips Consulting Limited | Professional & scientific | 2022 |
| Catherine Street Properties Limited | Construction | 2015 |
| Catherwood Estates (Belfast) Limited | Real estate | 1963 |
| Catian Solutions Ltd | Professional & scientific | 2023 |
| Catman Media Ltd | Information & communication | 2023 |
| Catney Ltd | Transport & logistics | 2022 |
| Cattle EYE Ltd | Information & communication | 2019 |
| Caught Drip’N’ Ltd | Wholesale & retail | 2023 |
| Cauldhill Limited | Real estate | 2012 |
| Cause (NI) Limited | Health & social care | 1995 |
| Causeway Alternative Fuels Limited | Other services | 2019 |
| Causeway Asset Management Limited | Real estate | 2014 |
| Causeway Business Group Limited | Hospitality | 2019 |
| Causeway Chemicals Ltd | Manufacturing | 2022 |
| Causeway Cleaning Services Ltd | Administrative & support | 2022 |
| Causeway Coast Developments Limited | Construction | 2017 |
| Causeway Constructino Ltd | Wholesale & retail | 2023 |
| Causeway E-Commerce Limited | Wholesale & retail | 2025 |
| Causeway Equipment Limited | Administrative & support | 1985 |
| Causeway Geothermal (NI) Ltd | Professional & scientific | 2021 |
| Causeway Investments Limited | Administrative & support | 2012 |
| Causeway Languages Ltd | Education | 2017 |
| Causeway Media Ltd | Information & communication | 2012 |
| Causeway Pictures Limited | Information & communication | 2009 |
| Causeway Public Affairs Consultancy Limited | Professional & scientific | 2015 |
| Causeway Recycling Ltd | Water & waste | 2025 |
| Causeway Rescue Ltd | Public administration | 2020 |
| Causeway Sensors Limited | Manufacturing | 2013 |
| Causeway Surgical Ltd | Health & social care | 2019 |
| Causeway Telecom Ltd | Information & communication | 2011 |