| Konstruct Interiors Ltd | Construction | 2018 |
| Konstruction Contract Services Ltd | Financial services | 2015 |
| Kottonology C.I.C. | Wholesale & retail | 2024 |
| Kova Recovery Limited | Other services | 2025 |
| Krafty Kitchens & Bedrooms Ltd | Manufacturing | 2014 |
| KRG Cars & Commercials Ltd | Wholesale & retail | 2025 |
| KRS 2025 Ltd | Financial services | 2025 |
| KRS N.I Ltd | Construction | 2025 |
| Kscd Properties Limited | Real estate | 2023 |
| KSM Commercials Ltd | Wholesale & retail | 2025 |
| KSM Lurgancot Ltd | Transport & logistics | 2016 |
| KTC Contracts Ltd | Construction | 2024 |
| L & M Properties (NI) Ltd | Real estate | 2014 |
| L Kerr & Co Ltd | Professional & scientific | 2010 |
| L33R Limited | Wholesale & retail | 2025 |
| Lagan Machinery Sales Ltd | Wholesale & retail | 2018 |
| Lakeside Enterprises (NI) Limited | Construction | 2014 |
| Lakeview Energy Ltd | Energy | 2024 |
| Lakeview Insurance Consultants Ltd | Financial services | 2022 |
| Langs Court Management Company Limited | Extraterritorial | 2004 |
| Lappin's Shop Limited | Wholesale & retail | 2026 |
| LC Contracts Ltd | Construction | 2025 |
| Leanne Loughran Consulting Ltd | Administrative & support | 2024 |
| Leder Construction and Civils Ltd | Construction | 2026 |
| Lenalea Electronics Limited | Manufacturing | 2000 |
| Lenalea Holdings Limited | Financial services | 2023 |
| Lenco Construction Limited | Construction | 1991 |
| Lenco Holdings Limited | Financial services | 2024 |
| Lennon Farms Ltd | Agriculture & fishing | 2026 |
| Lennon Hire Ltd | Transport & logistics | 2021 |
| Lerah Properties Ltd | Households | 2024 |
| Let's Sanitise IT Limited | Administrative & support | 2020 |
| Leten Animal Care Services | Professional & scientific | 2022 |
| Lets Recycle IT Limited | Water & waste | 2015 |
| LEV Air Solutions Limited | Manufacturing | 2012 |
| Levity Digital Ltd | Information & communication | 2019 |
| Lewis Property Agents Limited | Households | 2021 |
| Lewistown Limited | Professional & scientific | 2014 |
| LF Autos Limited | Wholesale & retail | 2022 |
| LFS Group Limited | Transport & logistics | 2015 |
| Liam Kerr & Co Limited | Professional & scientific | 2012 |
| Lilas (N.I.) Limited | Wholesale & retail | 2022 |
| Limavady Travel Ltd | Administrative & support | 2013 |
| Lime Grove Poultry Ltd | Agriculture & fishing | 2024 |
| Limes 1 Ltd | Real estate | 2025 |
| Linen Plant & Agri Ltd | Wholesale & retail | 2021 |
| Lisbanoe Hill Limited | Agriculture & fishing | 2025 |
| Lisburn Meadow Bakery Limited | Manufacturing | 2022 |
| Liskyborough Enterprises Limited | Hospitality | 2025 |
| Lislea Development Association Ltd | Other services | 2017 |
| Lislea Roots Ltd | Wholesale & retail | 2022 |
| Longnancy's Bar Ltd | Hospitality | 2020 |
| Lonsdale Fabrications Ltd | Manufacturing | 2016 |
| Lorsa Investments Ltd. | Professional & scientific | 2019 |
| Loughhill Properties Ltd | Real estate | 2005 |
| Loughran & Sons Transport Service Ltd | Transport & logistics | 2021 |
| Love Hockey Ireland | Arts & recreation | 2010 |
| LOW Mill Investments Ltd | Real estate | 2023 |
| LPG Refrigeration Services Limited | Manufacturing | 2013 |
| Lrmg Holdings Ltd | Financial services | 2025 |
| LTK Holdings Limited | Extraterritorial | 2019 |
| LTK Investments Limited | Real estate | 2019 |
| Lton Solicitors Limited | Professional & scientific | 2016 |
| Lubecare Ltd | Wholesale & retail | 2006 |
| Lubricant Distribution Ltd | Wholesale & retail | 2014 |
| Lucky Panda 76 Ltd | Hospitality | 2026 |
| Luman Shelving Ltd | Manufacturing | 2021 |
| Lurgancot Enterprises Limited | Professional & scientific | 2026 |
| Luxury Garlands Ltd | Professional & scientific | 2021 |
| M & C Bricklaying Limited | Construction | 2017 |
| M and M Ventures Inc Ltd | Information & communication | 2025 |
| M J Contracts (N.I.) Limited | Agriculture & fishing | 2019 |
| M J Ireland Limited | Transport & logistics | 2023 |
| M K Furnishings Ltd | Manufacturing | 2019 |
| M T Waste Management & Manufacturing Ltd | Manufacturing | 2001 |
| M Watson Transport Ltd | Transport & logistics | 2020 |
| M&E Utilities & Groundworks Limited | Construction | 2017 |
| M&G Mushrooms Limited | Agriculture & fishing | 2016 |
| M&N Plastering and Groundwork Limited | Construction | 2024 |
| M. Poultry Services (NI) Limited | Agriculture & fishing | 2011 |
| M. Reynolds Financial Solutions Limited | Financial services | 2005 |
| M.D Rafferty Music School Ltd | Arts & recreation | 2017 |
| MAC 1 Properties Ltd | Real estate | 2022 |
| MAC Electrics Ltd | Construction | 2012 |
| Mac-Trans International Limited | Transport & logistics | 2020 |
| Macbox 1 Limited | Real estate | 2025 |
| Macbox Limited | Real estate | 2023 |
| Macdara Ltd | Construction | 2025 |
| Mackin Enterprises Limited | Hospitality | 2024 |
| Mackle Farm Holdings Ltd | Financial services | 2018 |
| Mackle's Ice Cream Ltd | Wholesale & retail | 2020 |
| Macmar Properties Limited | Real estate | 2025 |
| Maco Contracts Ltd | Professional & scientific | 2015 |
| Macoo Ltd | Real estate | 2022 |
| Macray Properties Limited | Real estate | 2017 |
| Made for More 3D Ltd | Manufacturing | 2025 |
| Madec Design Services Ltd | Professional & scientific | 2012 |
| Maison Real Estate (NI) Limited | Real estate | 2018 |
| Mallon Coachworks Limited | Manufacturing | 2011 |
| Mallon Venture Group Ltd | Financial services | 2025 |