| J&G Eatery Ltd | Hospitality | 2017 |
| J. Arthur Electrical Ltd | Wholesale & retail | 2021 |
| J. Ferguson Roofing Contractors Ltd | Construction | 2021 |
| JAJ Mitch Ltd | Health & social care | 2024 |
| JAK Contracts Painting Ltd | Other services | 2015 |
| Jalu Enterprises Ltd | Financial services | 2005 |
| James Magee Plumbing & Heating Limited | Construction | 2025 |
| Jason Property Ltd | Households | 2026 |
| Jaspers Takeaway Limited | Wholesale & retail | 2019 |
| JAX Scaffolding INL Ltd | Construction | 2024 |
| JB Future Investments Ltd | Financial services | 2024 |
| JB Joe’S Bar Ltd | Hospitality | 2024 |
| JFA Group Holdings Ltd | Real estate | 2026 |
| JFC Apparel Sourcing Limited | Wholesale & retail | 2013 |
| JFE Contracts Ltd | Construction | 2026 |
| JG Building Contractors Ltd | Construction | 2015 |
| JGC Motors Limited | Wholesale & retail | 2015 |
| JJ Lafferty Ltd | Wholesale & retail | 2024 |
| JME Fibre Solutions Limited | Construction | 2022 |
| JMK Enterprises Limited | Wholesale & retail | 2002 |
| JOB Directions Limited | Administrative & support | 1995 |
| JOE Coyle Transport Ltd | Transport & logistics | 2015 |
| JOE Gallagher Entertainments Ltd | Arts & recreation | 2021 |
| JOE Mchugh Limited | Extraterritorial | 2018 |
| John Fahy & Co. Ltd | Professional & scientific | 2012 |
| John Mcglynn Transport Limited | Transport & logistics | 2018 |
| Jora Management Limited | Real estate | 2012 |
| JP MAC Promotions Limited | Information & communication | 2014 |
| JWS Benedict Limited | Real estate | 2016 |
| K and S Logan Ltd | Construction | 2020 |
| K Purwal Limited | Hospitality | 2020 |
| K&C Fuels Limited | Wholesale & retail | 2025 |
| KAI Houston Construction Limited | Construction | 2016 |
| Kane & Mchugh Plumbing & Heating Ltd | Construction | 2013 |
| Karagh Enterprises Ltd | Professional & scientific | 2023 |
| Karjon LLP | | 2025 |
| KBM Developments Ltd | Construction | 2019 |
| KCM Sales Limited | Wholesale & retail | 2019 |
| Kelgan Construction Limited | Construction | 2016 |
| Kelly & Co Ltd | Professional & scientific | 2013 |
| Kelly & Co North West Ltd | Professional & scientific | 2005 |
| Kelly Accountants Ltd | Professional & scientific | 2025 |
| Kelly Building Contractors Ltd | Construction | 2025 |
| Kelly BUS Hire Ltd | Transport & logistics | 2026 |
| Kellys Sand and Gravel Limited | Mining & quarrying | 2012 |
| Kernaglee Electrical Services Ltd | Construction | 2009 |
| KES Group Holdings Limited | Financial services | 2016 |
| KES Group Inc Ltd | Construction | 2014 |
| Keys Plastering Limited | Construction | 2017 |
| Kieran Cawley Motors Limited | Wholesale & retail | 2017 |
| Killenagh Hire & Sales Ltd | Administrative & support | 2019 |
| KMC Building Contracts Ltd | Construction | 2022 |
| KMG Painting Ltd | Construction | 2017 |
| Kodab Ltd | Construction | 2022 |
| Koram Energy Ltd | Extraterritorial | 2012 |
| Kotare Ventures Ltd | Real estate | 2025 |
| Kyle Crumley Dry-Lining Limited | Construction | 2025 |
| L H Motors IRE Limited | Wholesale & retail | 2014 |
| L H Motors IRL Limited | Wholesale & retail | 2025 |
| L J Millar and Sons (Holdings) Limited | Real estate | 2013 |
| L J Millar and Sons Limited | Construction | 2013 |
| L.A. Aesthetics & SMP Clinic Ltd | Other services | 2023 |
| Lake Consultancy and Training Limited | Professional & scientific | 2020 |
| Laurel Hill Enterprises Ltd | Other services | 2018 |
| LEA Building Maintenance Ltd | Real estate | 2023 |
| Leams Group Ltd | Financial services | 2023 |
| Leckpatrick Contract Services Ltd | Agriculture & fishing | 2025 |
| Leckpatrick Development Association | Other services | 2012 |
| Ledex Lighting UK Limited | Construction | 2022 |
| Leitch Trans Lift Limited | Construction | 2014 |
| LGS Building Solutions Ltd | Construction | 2018 |
| Liam Kelly Electrical Ltd | Construction | 2023 |
| Liam Kelly Haulage (UK) Limited | Transport & logistics | 2014 |
| Liam O'Neill Builders Limited | Construction | 2017 |
| Liam O'Neill Limited | Construction | 2003 |
| Lima Building Systems Ltd | Construction | 2008 |
| Lindsays Tullyard Ltd | Agriculture & fishing | 2026 |
| Linton & Robinson Environmental Ltd | Manufacturing | 2012 |
| Linton & Robinson Group Limited | Financial services | 2018 |
| Linton Environmental Ltd | Professional & scientific | 2014 |
| Lisa's Nails & Spa Ltd | Other services | 2025 |
| Lisagallon Cabling Contractors Ltd | Construction | 2016 |
| Liscloon Farm Ltd | Energy | 2012 |
| Lisglass Farms | Agriculture & fishing | 2017 |
| Lisglass Luxury Glamping Ltd | Hospitality | 2025 |
| Liskey Construction Limited | Construction | 2017 |
| Lisowen Management Company Limited | Households | 2021 |
| LJ Millar Agri Contracts Ltd | Administrative & support | 2018 |
| LJM Building Suppliers Ltd | Wholesale & retail | 2021 |
| LK Performance Parts Limited | Wholesale & retail | 2018 |
| LMC Car Sales Ltd | Wholesale & retail | 2025 |
| LMC Property Ltd | Real estate | 2021 |
| Locumcare Ltd | Administrative & support | 2025 |
| LONGITUDE-131 Ltd | Households | 2025 |
| Losev Limited | Wholesale & retail | 2012 |
| Loughrey Stores Ltd | Wholesale & retail | 2025 |
| LR Biogas Solutions Ltd | Manufacturing | 2014 |
| Lucky Star Strabane Limited | Hospitality | 2024 |
| Lucy Property Ltd | Construction | 2019 |
| Lynch Haulage Limited | Transport & logistics | 2024 |