| Leafair Well-Being Enterprises Ltd | Health & social care | 2020 |
| Leap Consulting Limited | Financial services | 2021 |
| Leap Lessons LLP | | 2024 |
| Learning Pool Limited | Education | 2006 |
| Leddy Engineering Consultants Ltd | Professional & scientific | 2022 |
| Leisure Construction Ltd | Construction | 2022 |
| Leprechaun Bakery & Coffee Shop Ltd | Wholesale & retail | 2018 |
| Let's Play Bingo Limited | Wholesale & retail | 2019 |
| LF Property Holdings Ltd | Real estate | 2025 |
| LFS CAW Ltd | Wholesale & retail | 2024 |
| LFS Coalisland Ltd | Wholesale & retail | 2022 |
| LFS Greysteel Ltd | Wholesale & retail | 2021 |
| LG Marine Services Limited | Agriculture & fishing | 2016 |
| Liberty Consortium | Health & social care | 2006 |
| Liberty Consortium Enterprises C.I.C. | Professional & scientific | 2013 |
| Lifestart Foundation Limited | Education | 2001 |
| Limavady Printing Company Limited | Manufacturing | 1974 |
| Limavady Road Developments Limited | Construction | 2014 |
| Limavady Road Properties Limited | Real estate | 2014 |
| Limavady Road Residential Limited | Construction | 2025 |
| Limewood Brae | Administrative & support | 2019 |
| Limitless Media Limited | Administrative & support | 1995 |
| Liquid Carbon Technologies UK Ltd | Professional & scientific | 2024 |
| Liquid Creations Ltd | Manufacturing | 2017 |
| Lisdavin Estate | Financial services | 2025 |
| Little Ease Films Ltd | Information & communication | 2008 |
| Little Orchids | Education | 2009 |
| Liveside Limited | Construction | 2011 |
| LK4 Limited | Hospitality | 2024 |
| LKZ Medical Ltd | Health & social care | 2021 |
| Llne Ltd | Professional & scientific | 2023 |
| LM Kelly Properties Ltd | Real estate | 2024 |
| LMB30 Ltd | Real estate | 2024 |
| LMB40 Ltd | Real estate | 2025 |
| LMC Drylining Ltd | Construction | 2011 |
| LMS Support Ltd | Hospitality | 2024 |
| Locate Estate Agents Limited | Real estate | 1991 |
| Lock Developments Ltd | Financial services | 2016 |
| LOD Mechanical Ltd | Construction | 2024 |
| Lodgecourt Agencies Limited | Real estate | 1989 |
| Logan Media Ltd | Information & communication | 2021 |
| Loinnir 2 Ltd | Professional & scientific | 2019 |
| Lone Moor Productions Limited | Arts & recreation | 2009 |
| Long Tower Youth Club Ltd | Other services | 2022 |
| Loose Banana Productions Ltd | Information & communication | 2025 |
| Lotus Nail Spa Ltd | Other services | 2023 |
| Loughlea Properties Ltd | Real estate | 2004 |
| Loughtrade Global Limited | Wholesale & retail | 2025 |
| Lowry Developments Limited | Construction | 2014 |
| LR Bishop Street Limited | Construction | 2025 |
| LS North West Limited | Real estate | 2024 |
| LSW Engineering Ltd | Professional & scientific | 2024 |
| LT Enterprises Ltd | Professional & scientific | 2019 |
| LTE Machinery (UK) Limited | Wholesale & retail | 2017 |
| Luxor Bathrooms Tiles and Design Limited | Wholesale & retail | 2022 |
| Luxury European Tours Ltd | Administrative & support | 2017 |
| Lynch Corporation Ltd | Real estate | 2024 |
| Lynch Windows (NI) Limited | Construction | 2020 |
| Lynch's Property Group Ltd | Real estate | 2004 |
| Lyttle Decorating Services Limited | Construction | 2019 |
| M & D Services (2008) Limited | Wholesale & retail | 2008 |
| M Forum Trading Limited | Administrative & support | 2004 |
| M Toland Properties Ltd | Real estate | 2022 |
| M.R. Concrete Limited | Construction | 1998 |
| MAC and Co Construction Ltd | Construction | 2023 |
| Macliner Ltd | Manufacturing | 2026 |
| Macrob Ltd | Hospitality | 2025 |
| Maghera Granite Developments Limited | Construction | 2005 |
| Manlor Trading Limited | Wholesale & retail | 2021 |
| Manorwood Development (Enniskillen) Limited | Households | 1999 |
| Marble Hill Soaps Limited | Manufacturing | 2005 |
| Marc-Five Limited | Manufacturing | 1963 |
| Martin Kelly Properties Limited | Wholesale & retail | 2001 |
| Martin Mcguinness Peace Foundation | Other services | 2019 |
| Martin O'Connor Contracts Ltd | Construction | 2019 |
| Mary D QP Limited | Administrative & support | 2018 |
| Mast Plant Hire Limited | Administrative & support | 2017 |
| Matchbox Youth Club Ltd | Other services | 2022 |
| Mawn Ltd | Professional & scientific | 2019 |
| Maydown Properties Ltd | Real estate | 2023 |
| Maydown Trading Ltd | Wholesale & retail | 2023 |
| MAZ Building Contractors Ltd | Construction | 2024 |
| MBV Investments Limited | Arts & recreation | 2011 |
| MBX Property Management Company Ltd | Households | 2024 |
| MC Feelys Ltd | Hospitality | 2003 |
| Mcallister Site Services Limited | Construction | 2014 |
| Mcateer Estancias Irlanda Ltd | Hospitality | 2024 |
| Mcclafferty Funeral Directors Ltd | Other services | 2019 |
| Mcclean Electrics Ltd | Construction | 2023 |
| Mccloskey Holdings Ltd | Financial services | 2021 |
| Mccloskey Properties (Cool) Ltd | Construction | 2021 |
| MCD Corporate Hospitality Ltd | Professional & scientific | 2026 |
| MCD Enterprises Ltd | Hospitality | 2019 |
| MCD Retail Ltd | Hospitality | 2023 |
| Mcdaid Mortgages Ltd | Financial services | 2023 |
| Mcdaid Plant & Stone Limited | Mining & quarrying | 2023 |
| Mcdaid Property Services Ltd | Real estate | 2026 |
| MCG Contracts Holdings Limited | Construction | 2024 |
| Mcgee Solicitors Ltd | Professional & scientific | 2020 |
| Mcgonagle BUS & Coach Hire Limited | Transport & logistics | 2012 |