| Lenaderg Developments Limited | Wholesale & retail | 2005 |
| Lennon Concrete Flooring Specialists Ltd | Construction | 2019 |
| Letfern Properties Limited | Real estate | 2007 |
| Letfern Utilities Ltd | Construction | 2021 |
| Lettergesh Properties Ltd | Construction | 2012 |
| Lewara Limited | Financial services | 2024 |
| LFM Business Services Ltd | Information & communication | 2016 |
| LGS Modular Ltd | Manufacturing | 2020 |
| Liam Bradley Farm Limited | Agriculture & fishing | 2013 |
| Liam Bradley Ltd | Wholesale & retail | 1999 |
| Liffer Legal Limited | Professional & scientific | 2016 |
| Lightweight Aggregates Ireland Ltd | Other services | 2009 |
| Limitless Bags Limited | Wholesale & retail | 2013 |
| Limound Limited | Wholesale & retail | 2024 |
| Lionsgate Properties Ltd | Real estate | 2018 |
| Lisa Hutton Property Ltd | Real estate | 2021 |
| Lisahoppin Wind Limited | Energy | 2014 |
| Lisbellaw Medical Hall Ltd | Wholesale & retail | 2009 |
| Lismore Stables Ltd | Education | 2022 |
| Lisnafin Accountancy Services Ltd | Professional & scientific | 2022 |
| Lissan Properties Omagh Limited | Real estate | 2018 |
| Lithionsim Ltd | Professional & scientific | 2023 |
| Livonso Limited | Financial services | 2024 |
| LM Agri Services Ltd | Construction | 2024 |
| LMB Property & Investments Ltd | Real estate | 2026 |
| LMM Training Ltd | Education | 2022 |
| LMR Poultry Ltd | Agriculture & fishing | 2015 |
| LMS Electrics Ltd | Construction | 2017 |
| Logan and Corry LLP | | 2021 |
| Logan Performance Consulting Ltd | Professional & scientific | 2022 |
| Longhill Electrical Ltd | Construction | 2016 |
| Longhill Plant Services Ltd | Manufacturing | 2013 |
| Longhill Plant Services UK Ltd | Wholesale & retail | 2025 |
| Louerne Construction Limited | Construction | 1980 |
| Lough Mallon Quarry Limited | Water & waste | 2014 |
| Lough Mallon Recycling Limited | Water & waste | 2017 |
| Lough Solutions Ltd | Professional & scientific | 2016 |
| Lough Technologies Ltd. | Information & communication | 2016 |
| Loughmacrory Community Development Association | Professional & scientific | 2001 |
| Loughmacrory Management Company Limited | Construction | 2014 |
| Loughran Quarries Ltd | Other services | 2020 |
| Loughran Rock Quarries Ltd | Mining & quarrying | 2012 |
| Loughside Boat Sales Ltd | Manufacturing | 2025 |
| Loughtec Limited | Information & communication | 2006 |
| Loughview Meadows Management Ltd | Households | 2017 |
| Loughview Power Ltd | Construction | 2025 |
| Loughwood Fabrication Ltd | Manufacturing | 2026 |
| Loukelemm Properties Ltd | Real estate | 2017 |
| Love Utility Services Ltd | Professional & scientific | 2024 |
| LPE Plant Limited | Administrative & support | 2013 |
| Ltaf Properties Ltd | Real estate | 2026 |
| LTF Holdings Ltd | Financial services | 2026 |
| Luvly Ltd | Wholesale & retail | 2026 |
| Lyons and Wards Woodcraft Limited | Manufacturing | 2010 |
| M & a Gunna Consulting Ltd | Administrative & support | 2016 |
| M & C O'Neill Ltd | Construction | 2004 |
| M & E Winters Ltd | Wholesale & retail | 2021 |
| M & K Electrical Ltd | Construction | 2010 |
| M & L Services Omagh Ltd | Professional & scientific | 2021 |
| M & TM Bar Ltd | Hospitality | 2026 |
| M Caldwell Shuttering and Plant Ltd | Construction | 2026 |
| M Donnelly Motors Ltd | Wholesale & retail | 2026 |
| M Ferrity Plant Hire Limited | Administrative & support | 2014 |
| M Mcnulty Engineering Ltd | Manufacturing | 2011 |
| M Winters Electrical Limited | Construction | 2009 |
| M&D Contracts Group Ltd | Construction | 2026 |
| M&F NI Holdings Ltd | Financial services | 2021 |
| M&L Autoparts Limited | Wholesale & retail | 2010 |
| M4T (N.Ireland) Ltd | Wholesale & retail | 2021 |
| MAC Aleer Group Ltd | Transport & logistics | 2024 |
| MAC Core Limited | Construction | 2021 |
| MAC Ecoenergy Solutions Limited | Construction | 2026 |
| MAC Farms Ltd | Agriculture & fishing | 2010 |
| MAC Fuels (N.I.) Ltd | Wholesale & retail | 2017 |
| MAC Green Energy Innovation Limited | Construction | 2026 |
| MAC Plant Hire & Utilities Limited | Construction | 2022 |
| MAC Strength Gym Equipment Ltd | Wholesale & retail | 2020 |
| Maccrossan Healthcare Limited | Financial services | 2025 |
| Macrea Group Limited | Construction | 2024 |
| Macs Auto Centre Ltd | Wholesale & retail | 2023 |
| Magee Construction Services Ltd | Construction | 2025 |
| Maguire Plastering IRE Ltd | Construction | 2021 |
| Maguire Property Ltd | Real estate | 2018 |
| MAH (Tyrone) Limited | Hospitality | 2016 |
| Mahoney Contracts (N.I.) Ltd | Construction | 2023 |
| Main Street Stores Ltd | Wholesale & retail | 2016 |
| Major Drilling (NI) Limited | Mining & quarrying | 2010 |
| MAK Contracts Ltd | Construction | 2019 |
| MAK Inspection Services Ltd | Construction | 2026 |
| Makers of Ireland Limited | Wholesale & retail | 2014 |
| Makeway International Limited | Wholesale & retail | 2019 |
| Malabhui Properties Ltd | Real estate | 2024 |
| Malmac Ltd | Hospitality | 2022 |
| Mamamigo Ltd | Manufacturing | 2014 |
| Manor Corporate Limited | Other services | 2016 |
| Mantleplastering Ltd | Construction | 2021 |
| Marcor Holdings Ltd | Financial services | 2021 |
| Marcor Limited | Construction | 2009 |
| Marcor Properties Ltd | Real estate | 2019 |
| Mardec Drywall Systems Limited | Construction | 2017 |