| L.G. Fire Protection (N.I.) Ltd | Construction | 2021 |
| L4L Ltd | Wholesale & retail | 2025 |
| LA Rousse Foods (N.I.) Limited | Hospitality | 1997 |
| Lacsina Ltd | Administrative & support | 2023 |
| Lady B Piercings Ltd | Other services | 2024 |
| Lagan Blue Limited | Real estate | 2024 |
| Lagan Construction Express Limited | Construction | 2025 |
| Lagan Motor Factors (Lisburn) Limited | Wholesale & retail | 2020 |
| Lagan Oils Limited | Wholesale & retail | 2009 |
| Lagan Regional Transport C.I.C. | Transport & logistics | 2012 |
| Lagan Valley Property Ltd | Real estate | 2024 |
| Lagan Valley Rural Transport | Transport & logistics | 2005 |
| Lagan Valley Scientific Limited | Professional & scientific | 2020 |
| Lagan Wholesale Furniture Ltd | Wholesale & retail | 2009 |
| Laganside Business Services Limited | Administrative & support | 2001 |
| Laganside Wholesale Limited | Wholesale & retail | 2010 |
| Laganvale Farm Ltd | Hospitality | 2026 |
| Laganview Enterprise Centre Limited | Administrative & support | 2004 |
| Laganview Golf Centre Ltd | Arts & recreation | 2005 |
| Lakefront Property Development Limited | Construction | 2017 |
| Lambeg Energy Limited | Energy | 2025 |
| Lambeg Golf Shop Limited | Wholesale & retail | 2015 |
| Lambeg Property Services Ltd | Administrative & support | 2026 |
| LAN Ting BFS Ltd | Hospitality | 2026 |
| Landow Real Estate LLP | | 2017 |
| Landscape Trends LP | | 2017 |
| Lann Bheag Ltd | Financial services | 2022 |
| Larch Hill Farms Limited | Administrative & support | 1996 |
| Larchfield Estate LLP | | 2023 |
| Large Waves Properties Limited | Real estate | 2008 |
| Lariba Foods Limited | Hospitality | 2025 |
| Larkfield Structures Ltd | Construction | 2022 |
| Larkin Safety Resources Limited | Professional & scientific | 2017 |
| Larne Battery Storage Limited | Energy | 2020 |
| Larsen Contracts Limited | Construction | 1985 |
| Larsen Foundations Limited | Construction | 1991 |
| Lateral Technologies Ltd | Information & communication | 2018 |
| Laurel Hill Poultry Ltd | Agriculture & fishing | 2025 |
| Law Commercials Ltd | Wholesale & retail | 2013 |
| LCC Community Trust | Health & social care | 2015 |
| League Pickleball Ltd | Arts & recreation | 2025 |
| Leakproof Pods Ltd | Manufacturing | 2025 |
| Lean Fourteen Ltd | Hospitality | 2019 |
| Learners R US Ltd | Education | 2017 |
| Lebony Limited | Real estate | 2014 |
| Leckatreena Holdings Ltd | Financial services | 2019 |
| LEE and Wong Properties & Rental Investment Ltd | Real estate | 2002 |
| Legacy Score Ltd | Information & communication | 2018 |
| Leisure Technical Solutions Ltd | Wholesale & retail | 2016 |
| Lennon Homes Ltd | Construction | 2002 |
| Lenwood Construction Ltd | Construction | 2022 |
| LEO Foster Ltd | Transport & logistics | 2025 |
| Leonard Mckee Ltd | Wholesale & retail | 2021 |
| Leozone Limited | Financial services | 2021 |
| Leslie Sterrit Fashion Shoes | | 2003 |
| LET Ready Floors Ltd | Construction | 2025 |
| Leveling LP | | 2022 |
| Levente Ventures Limited | Information & communication | 2024 |
| Lewcose Limited | Wholesale & retail | 2025 |
| Lewis Tower Crane Services Ltd | Administrative & support | 2010 |
| Lexson Holdings Ltd | Wholesale & retail | 2025 |
| LGM Courier Services Ltd | Transport & logistics | 2026 |
| Libero Business Services Limited | Information & communication | 2014 |
| Liffey & Lagan Ltd | Construction | 2026 |
| Lifting Giants Ltd | Manufacturing | 2023 |
| Lighthouse Trading Company Ltd | Extraterritorial | 2001 |
| Lihuxa Ltd | Wholesale & retail | 2024 |
| Like Magic Ltd | Professional & scientific | 2026 |
| Lilley Fine Art Ltd | Wholesale & retail | 2013 |
| Lilley Holding Company Limited | Wholesale & retail | 2018 |
| Limestone Development LLP | | 2017 |
| Limestone Property Development (UK) Limited | Real estate | 2017 |
| LIN 521 Ltd | Hospitality | 2024 |
| Linder Contracts Limited | Construction | 1981 |
| Linen Mews Apartments Limited | Households | 2023 |
| Lingo Ltd | Information & communication | 2024 |
| Linian Software Ltd | Information & communication | 2010 |
| Link Community Care (NI) Ltd | Health & social care | 2019 |
| Linktap PTY Ltd | Wholesale & retail | 2025 |
| Linton Fencing & Sportsgrounds Limited | Construction | 2020 |
| Linton Technical Solutions Limited | Manufacturing | 2021 |
| Linzi Hoare Brows Limited | Other services | 2021 |
| Lion Medical Services Limited | Health & social care | 2019 |
| Lions Smart Solutions LP | | 2022 |
| Lion’S DEN Logistics Ltd | Transport & logistics | 2025 |
| Lisa Trinder Video Ltd | Information & communication | 2013 |
| Lisburn Accident Repair Centre Ltd | Wholesale & retail | 2020 |
| Lisburn Auto Salvage Limited | Wholesale & retail | 2010 |
| Lisburn Bargain Limited | Wholesale & retail | 2026 |
| Lisburn Blinds Ltd | Construction | 2025 |
| Lisburn Bowl Limited | Arts & recreation | 2013 |
| Lisburn Buildings Preservation Trust | Construction | 2002 |
| Lisburn Community Inns Ltd | Hospitality | 2007 |
| Lisburn Community Self Build Ltd | Construction | 2000 |
| Lisburn Computer Repairs Ltd | Wholesale & retail | 2016 |
| Lisburn Electrical Contracts Limited | Construction | 2020 |
| Lisburn Enterprise Organisation Limited | Real estate | 1990 |
| Lisburn Hearing Limited | Wholesale & retail | 2022 |
| Lisburn Logistics Ltd | Transport & logistics | 2021 |
| Lisburn Music Centre Limited | Arts & recreation | 2016 |