| Jetmac Limited | Wholesale & retail | 2017 |
| JFO Consultancy Ltd | Information & communication | 2024 |
| JIM Ireland Architects Limited | Professional & scientific | 2010 |
| JMB Joinery Contracts Ltd | Construction | 2017 |
| JMJ Property Maintenance Ltd | Construction | 2023 |
| JMK Quads Ltd | Wholesale & retail | 2014 |
| JMK Solutions Ltd | Information & communication | 2013 |
| John Higgins Ltd | Extraterritorial | 2024 |
| John Morgan Wealth Management Ltd | Financial services | 2020 |
| Johnsfield Limited | Extraterritorial | 2011 |
| Jone Store Limited | Wholesale & retail | 2026 |
| Jons Civil Engineering (NI) Limited | Construction | 2021 |
| Joseph Charles Gerard Mcevoy Ltd | Agriculture & fishing | 2025 |
| JP Trading 3 Limited | Professional & scientific | 2016 |
| JP Trading 4 Limited | Professional & scientific | 2016 |
| Jrsh Investments Ltd | Real estate | 2019 |
| JRT Lifting Limited | Administrative & support | 2017 |
| JTC Joinery Ltd | Construction | 2019 |
| Juniper Investments Limited | Real estate | 2003 |
| Just Cooked Ltd | Hospitality | 2019 |
| Just Property Rents Limited | Real estate | 2023 |
| K M Building (2017) Ltd | Construction | 2017 |
| K M Engineering Ireland Ltd | Professional & scientific | 2020 |
| K Riley PH Services Ltd | Construction | 2025 |
| K. Mackin Transport Ltd | Transport & logistics | 2005 |
| Kane Group Building Services Ltd | Construction | 2003 |
| Karalee Investments Limited | Real estate | 2017 |
| Karen Flowers Ltd | Wholesale & retail | 2019 |
| Karpa Johanna Ltd | Wholesale & retail | 2023 |
| Katesbridge PIG Farm Ltd | Agriculture & fishing | 2020 |
| Katriona Ltd | Wholesale & retail | 2001 |
| Kbros Foods Limited | Wholesale & retail | 2025 |
| Kcmg Properties Limited | Households | 2023 |
| Keith Graham Contracts Ltd | Construction | 2018 |
| Kelly Bookmakers Limited | Arts & recreation | 2022 |
| Keymac Developments Limited | Construction | 2019 |
| Keystone Learning Academy Limited | Education | 2026 |
| KG Byrne & Associates Limited | Administrative & support | 2002 |
| Kieran Martin Gerard Byrne Ltd | Extraterritorial | 2024 |
| Killuney Homes Ltd | Construction | 2015 |
| Killyleen Ltd | Real estate | 2019 |
| Kimia Aesthetics Limited | Health & social care | 2025 |
| Kingsmere Investments Limited | Real estate | 2022 |
| Kinlough Limited | Agriculture & fishing | 2014 |
| Kirkpatrick Rental Company Ltd | Real estate | 2024 |
| Kliperz Limited | Other services | 2014 |
| KMC Agri Ltd | Wholesale & retail | 2015 |
| KMG Contracting Limited | Construction | 2021 |
| Knight Design & Fabrication Ltd | Manufacturing | 2023 |
| Knight Truck Parts Ltd | Wholesale & retail | 2021 |
| Knightsbridge Clinic Group Ltd | Hospitality | 2020 |
| Knowledge Fitness Gym Ltd | Arts & recreation | 2015 |
| Kwikplumb Ltd | Wholesale & retail | 2023 |
| KYM Construction Ltd | Construction | 2024 |
| L & E Properties Limited | Construction | 2003 |
| LA Boda Bridal Ltd | Wholesale & retail | 2017 |
| LA Catalina Co Ltd | Wholesale & retail | 2010 |
| Lacoste Accountancy Services Limited | Professional & scientific | 2018 |
| Ladybelle Bridal Ltd | Wholesale & retail | 2011 |
| Ladybird Lane Ltd | Health & social care | 2006 |
| Lalapanzi (Banbridge) Ltd | Wholesale & retail | 2015 |
| Largy Road Limited | Administrative & support | 2019 |
| Larmac Construction Ltd | Extraterritorial | 2000 |
| Lauren Thomas Limited | Wholesale & retail | 2022 |
| Layerthree Consultancy Ltd | Information & communication | 2026 |
| Leadership Excellence Limited | Administrative & support | 2015 |
| Legananny Renewables Ltd | Energy | 2013 |
| LH19 Retail Ltd | Wholesale & retail | 2022 |
| Limpeeze Ltd | Wholesale & retail | 2015 |
| Linen Homes N.I. Limited | Real estate | 2017 |
| Linen Mill Studios Ltd | Arts & recreation | 1971 |
| Lion’S EYE Property Ltd | Construction | 2026 |
| Lipo TUC Ltd | Other services | 2020 |
| Liquid Acquire Ltd | Professional & scientific | 2024 |
| Lisieux Properties Limited | Real estate | 2021 |
| Lisnavaghrog Retail Ltd | Wholesale & retail | 2021 |
| Little Forest Studio Ltd | Information & communication | 2018 |
| Livistona Limited | Administrative & support | 2023 |
| LL Accessories Ltd | Manufacturing | 2022 |
| Lorstev Construction Ltd | Construction | 2012 |
| Lorstev Developments Ltd | Construction | 2016 |
| Lotus Finco Limited | Financial services | 2019 |
| Lotus Property (N.I.) Limited | Real estate | 2016 |
| Lotus Property Holdco Limited | Financial services | 2019 |
| Loughbrickland Management Limited | Households | 2017 |
| Loughbridge Construction Ltd | Construction | 2026 |
| Loughwood Ltd | Manufacturing | 2005 |
| Love LU Beauty Ltd | Other services | 2023 |
| Lowe SOT Limited | Wholesale & retail | 2000 |
| Lpfretail Ltd | Wholesale & retail | 2023 |
| Lpsd Financial Ltd | Financial services | 2025 |
| Lshouse Limited | Agriculture & fishing | 2022 |
| Lushomes Ltd | Real estate | 2015 |
| Luxe Sunbeds Limited | Arts & recreation | 2021 |
| Luxe Tanning Beds Limited | Other services | 2025 |
| M B Imports Limited | Wholesale & retail | 2024 |
| M R Thompson Ltd | Administrative & support | 2017 |
| M&D Property Rentals Limited | Real estate | 2021 |
| M&G Kerr Properties Ltd | Real estate | 2014 |
| M.S.M. (Contracts) Ltd | Construction | 1985 |