| Kjnc Estates Limited | Real estate | 2005 |
| Kljf Ltd | Manufacturing | 2023 |
| Kotec Ceramic Coatings Ltd | Information & communication | 2023 |
| L a W Properties UK Limited | Extraterritorial | 2007 |
| L and F (N.I.) Ltd | Manufacturing | 2019 |
| L.S Restorations Ltd | Wholesale & retail | 2020 |
| Laketorrent Limited | Construction | 2017 |
| Landfill GAS Generation Limited | Energy | 2008 |
| Lansdowne Manor Apartments Limited | Extraterritorial | 2003 |
| Larne Chemists Limited | Health & social care | 1998 |
| Larne Community Football Limited | Arts & recreation | 2017 |
| Larne Dog Walking Limited | Agriculture & fishing | 2022 |
| Larne Engineering Limited | Manufacturing | 2023 |
| Larne Football Club (NI) | Arts & recreation | 2014 |
| Larne Golf Club, Limited - the | Arts & recreation | 1941 |
| Larne Harbour Limited | Transport & logistics | 1912 |
| Larne Investments Limited | Real estate | 2025 |
| Larne Lakers Sports Club Ltd | Arts & recreation | 2025 |
| Larne Lough Nurseries Ltd | Agriculture & fishing | 2015 |
| Larne Skills Development Limited | Real estate | 1991 |
| Larne Specsavers Limited | Wholesale & retail | 2012 |
| Larne Taxi Co Ltd | Transport & logistics | 2023 |
| Larne Ymca Enterprises Ltd | Wholesale & retail | 2024 |
| Latharna Limited | Extraterritorial | 2008 |
| Laurel Property Management Company Limited | Households | 2018 |
| Lcog Ltd | Wholesale & retail | 2022 |
| LEE Family Printing Ltd | Wholesale & retail | 2026 |
| Lehding Services Design Ltd | Professional & scientific | 2003 |
| Leisure Homes Ireland Ltd | Hospitality | 2010 |
| Leitchfans Ltd | Wholesale & retail | 2025 |
| Leonard Swan & Sons Developments Limited | Other services | 2004 |
| Lghjm Ltd | Wholesale & retail | 2023 |
| Link Switchgear Limited | Manufacturing | 2025 |
| Lisnamoylehouse Limited | Hospitality | 2025 |
| Little Einsteins Facilities Ltd | Education | 2024 |
| Little Larne Ltd | Real estate | 2014 |
| LJC (N.I.) Ltd | Construction | 2023 |
| LK Engineering (N.I.) Ltd | Manufacturing | 2020 |
| Local Economic Development Company (Ledcom) Limited | Real estate | 1985 |
| Lockstown Engineering Ltd | Professional & scientific | 2024 |
| Loft Health & Beauty Limited Liability Partnership | | 2024 |
| Logistics Training Solutions(Europe) Ltd | Professional & scientific | 2024 |
| Longmore Electronics Limited | Manufacturing | 1994 |
| Looney & Mcalister Ltd | Construction | 2015 |
| Lowe's of Larne Ltd | Wholesale & retail | 2011 |
| Lpmcni Ltd | Professional & scientific | 2026 |
| LR (N.I.) Ltd | Hospitality | 2018 |
| LSD EOT Limited | Extraterritorial | 2022 |
| Luing Enterprises Limited | Professional & scientific | 2018 |
| Luing Services Ltd | Extraterritorial | 2020 |
| Lybb Ltd | Professional & scientific | 2023 |
| Lyle Farms Ltd | Agriculture & fishing | 2018 |
| M Alliance (NI) Ltd | Professional & scientific | 2014 |
| M&Dt Plumbing and Heating Ltd | Construction | 2021 |
| M.T.A Consultancy Ltd | Professional & scientific | 2018 |
| MAC NI Security Limited | Administrative & support | 2025 |
| Macallister Mcaleese Solicitors (EW) Limited | Professional & scientific | 2022 |
| Macallister Mcaleese Solicitors Limited | Professional & scientific | 2020 |
| Mackenzie's Equestrian Centre Ltd | Agriculture & fishing | 2014 |
| Macrory Property Investments Ltd | Real estate | 2025 |
| Maestro Enterprises Ltd | Hospitality | 2017 |
| Magee Groundworks Ltd | Administrative & support | 2024 |
| Magell (Magheramorne Estate) Limited | Real estate | 2020 |
| Magheralin Energy Limited | Energy | 2022 |
| Magheramore Energy Limited | Energy | 2022 |
| Magheramorne Holdings Limited | Financial services | 2020 |
| Mahee Services Ltd | Extraterritorial | 2020 |
| Mahee Solutions Ltd | Manufacturing | 2018 |
| Maidens Management Limited | Real estate | 2005 |
| Maidens View Management Company Limited | Households | 2018 |
| Majestic Nail & Beauty Boutique Ltd | Other services | 2017 |
| Majo (Global) Ltd | Other services | 2021 |
| Major TOM Clothing Limited | Wholesale & retail | 2019 |
| Make UP Pro Store (Derry) Ltd | Other services | 2015 |
| Make UP Pro Store Newry Ltd | Other services | 2013 |
| Malcolmsonc Limited | Professional & scientific | 2018 |
| Malfi Limited | Professional & scientific | 1996 |
| Maljac Limited | Construction | 2023 |
| Mambo Life Ltd | Wholesale & retail | 2024 |
| Mammbo Trading Limited | Wholesale & retail | 2025 |
| Mann Catering Ltd | Wholesale & retail | 2016 |
| Manna Developments Limited | Construction | 2006 |
| Manso Bros Ltd | Real estate | 2020 |
| Manso Property Ltd | Real estate | 2018 |
| Marac Ltd | Manufacturing | 2019 |
| Mastercraft Plumbing Limited | Construction | 2026 |
| Mayur Indian Takeaway Larne Ltd | Hospitality | 2026 |
| MBA Inver Investments Limited | Hospitality | 2018 |
| Mbhair Ltd | Other services | 2016 |
| MBW Engineering Ltd | Manufacturing | 2024 |
| Mcadam GRP Limited | Professional & scientific | 2019 |
| Mcauley Inspection NI Limited | Professional & scientific | 2015 |
| MCC DP Ltd | Construction | 2019 |
| Mccutcheon Media Limited | Information & communication | 2022 |
| Mcdonald Contracts Ltd | Manufacturing | 2020 |
| Mcdowells Bakery Ltd | Hospitality | 2015 |
| Mcgoogan Paving Ltd | Administrative & support | 2020 |
| Mckeown Contracts Ltd | Manufacturing | 2024 |
| Mckillop Properties Ltd | Real estate | 2000 |
| Mcmasters Home Farm Meats Limited | Wholesale & retail | 2022 |