| L J T B Limited | Wholesale & retail | 2020 |
| L Patterson Training Ltd | Health & social care | 2024 |
| L&B Ecom Limited | Wholesale & retail | 2025 |
| L&L Retail Ltd | Wholesale & retail | 2025 |
| Laganview Associates Limited | Information & communication | 2013 |
| Laird Law Male Grooming Ltd | Other services | 2022 |
| Lamont Industrial Limited | Wholesale & retail | 2016 |
| Landgen Ltd | Professional & scientific | 2020 |
| Lane Productions Ltd | Arts & recreation | 2024 |
| Laragh Lodge Ltd | Hospitality | 2022 |
| Laragh Restaurant Ltd | Hospitality | 2025 |
| Largy Properties Limited | Construction | 2012 |
| Largy Road Filling Station Limited | Wholesale & retail | 2023 |
| Lasta Woodpellets Ltd | Extraterritorial | 2016 |
| Latner 10 Developments Ltd | Households | 2008 |
| Laura Dallat Interiors Limited | Professional & scientific | 2016 |
| Lavada Talent Ltd | Professional & scientific | 2014 |
| Lavin Enterprises Ltd | Wholesale & retail | 2009 |
| LCS Electrical Limited | Construction | 2006 |
| LDC Incorporated Ltd | Real estate | 2022 |
| LE Jardin Sauvage Ltd | Wholesale & retail | 2019 |
| Leaf Designs (2022) Ltd | Wholesale & retail | 2022 |
| Leap Software Solutions Ltd | Information & communication | 2023 |
| Leash Holdings Limited | Financial services | 2026 |
| LEE Stewart Developments Limited | Construction | 2018 |
| Lees Investments Ltd | Real estate | 2002 |
| Lesmar Coast Ltd | Hospitality | 2023 |
| Lexi (N.I.) Ltd | Wholesale & retail | 2020 |
| LGP Contracts Limited | Construction | 2020 |
| Lgsports Ltd | Wholesale & retail | 2014 |
| LHA Homes Ltd | Real estate | 2020 |
| LHA Press Limited | Wholesale & retail | 2019 |
| Lifestyle Gymnastics Academy C.I.C. | Arts & recreation | 2022 |
| Lightup Live! (N.I.) Ltd | Arts & recreation | 2023 |
| Lignamonagh Woodworx Ltd | Construction | 2026 |
| Lilyash Holdings Limited | Financial services | 2024 |
| Lilyash Limited | Construction | 2016 |
| Limes Business Park Limited | Real estate | 2021 |
| Linkbox Holdings NI Limited | Extraterritorial | 1985 |
| Linkbox Investments Limited | Financial services | 2024 |
| Lisbreen Developments Limited | Construction | 2014 |
| Lisbreen Homes Limited | Construction | 2012 |
| Lismoyle Engineering Co Ltd | Manufacturing | 2003 |
| Lisnabann Power Services Ltd | Energy | 2011 |
| Lisnagreen Energy Ltd | Energy | 2013 |
| Lisnamurrican Veterinary Ltd | Professional & scientific | 2022 |
| Lisnatrew Manor Management Limited | Households | 2007 |
| Lisohn Dawn Limited | Extraterritorial | 1985 |
| Lissanoure Castle Limited | Hospitality | 1997 |
| Lissanoure Farms, Limited | Agriculture & fishing | 1945 |
| Live Fleet Solutions Ltd | Manufacturing | 2023 |
| LJD Retail Limited | Wholesale & retail | 2022 |
| LM Paints Limited | Wholesale & retail | 2023 |
| LMD Catering Ltd | Manufacturing | 2023 |
| LMD Cosmetics Ltd | Wholesale & retail | 2018 |
| LMD Holdings Ltd | Financial services | 2021 |
| LMD Products Ltd | Wholesale & retail | 2017 |
| LO Carbon Cattle Company Ltd | Agriculture & fishing | 2020 |
| Loan and Lecale Ltd | Professional & scientific | 2021 |
| Lockbox (NI) Limited | Administrative & support | 2014 |
| Loft Estates Ltd | Construction | 2010 |
| Loft Holdings Investments Ltd | Financial services | 2024 |
| Logan Contracts Joinery and Building Contractors Ltd | Construction | 2004 |
| Logans Executive Travel Limited | Wholesale & retail | 2012 |
| Logicmarkets (NI) Ltd | Financial services | 2024 |
| London H2 O Limited | Construction | 2018 |
| Loneva Ltd | Other services | 2005 |
| Long ARM Distributing Ltd | Wholesale & retail | 2022 |
| Long Lane Capital Limited | Professional & scientific | 2026 |
| Long Lane Group Holdings Limited | Financial services | 2026 |
| Longfield Park Management Company Ltd | Extraterritorial | 2010 |
| Lorimer Contracts Limited | Construction | 2016 |
| Lough and Valley Care Services Ltd | Health & social care | 2026 |
| Loughshore Manor Properties Limited | Real estate | 2022 |
| Loughview Renewable Energy Limited | Energy | 2011 |
| Love Property (NI) Ltd | Real estate | 2013 |
| Lovedale Healthcare Solutions Ltd | Health & social care | 2023 |
| LOW Carbon Cattle Company Ltd | Agriculture & fishing | 2020 |
| LP Chalice Ltd | Transport & logistics | 2025 |
| LPL Property Development Limited | Real estate | 2016 |
| LSG Consulting Ltd | Professional & scientific | 2023 |
| Ltd Group Holdings Limited | Administrative & support | 2022 |
| Lucatess Property Ltd | Administrative & support | 2023 |
| Lumi Windows Limited | Manufacturing | 2017 |
| Lyle Contracts Ltd | Construction | 2023 |
| Lyle Properties (N.I.) Limited | Real estate | 2024 |
| Lyle Utilities Limited | Construction | 2021 |
| Lyness Utility Services Ltd | Information & communication | 2017 |
| Lynn & Brewster Investments Ltd | Real estate | 2019 |
| Lynn & Brewster Ltd | Real estate | 2014 |
| Lynne Graham Ltd | Arts & recreation | 2017 |
| Lyttle Smart Homes Ltd | Construction | 2021 |
| M & H (2024) Ltd | Hospitality | 2024 |
| M Clarke & Sons Limited | Construction | 2023 |
| M Dennison Haulage Limited | Transport & logistics | 2026 |
| M Mcerlean Joinery & Construction Ltd | Construction | 2018 |
| M Thompson Property Ltd | Real estate | 2025 |
| M. Clarke & Sons Contracts Limited | Construction | 2005 |
| M.Hasson and Sons Limited | Manufacturing | 1977 |
| M3 Distribution Services Limited | Wholesale & retail | 2005 |