| Journey Community Church | Other services | 2013 |
| Jpconnell Financial Ltd | Financial services | 2018 |
| JR Motors Belfast Ltd | Wholesale & retail | 2024 |
| JS Holdco Ltd | Financial services | 2025 |
| JSK & SJK Limited | Professional & scientific | 2012 |
| JSS Partnership Limited | Financial services | 2021 |
| Jungle Quest Ltd | Wholesale & retail | 2025 |
| Just a WEE Baker Ltd | Manufacturing | 2020 |
| K. Allen Ltd | Construction | 2007 |
| K2 Facades Ltd | Construction | 2022 |
| K2I-EOC Ltd | Professional & scientific | 2024 |
| KAF Holdings Limited | Real estate | 2016 |
| Kaioptix Ltd | Manufacturing | 2023 |
| Kallingal Ltd | Health & social care | 2024 |
| Kantona Limited | Construction | 2016 |
| Karl Asset Management Ltd | Professional & scientific | 2013 |
| Karl Developments Ltd | Real estate | 1998 |
| Karl Property Investments Limited | Construction | 2011 |
| Keep IT Simple Bookkeeping Ltd | Professional & scientific | 2016 |
| Kelly PR Ltd | Professional & scientific | 2003 |
| Kenrondiagnostics Ltd | Manufacturing | 2026 |
| Kerr Signs Ltd | Manufacturing | 2013 |
| Kerr's Tyres Limited | Wholesale & retail | 2009 |
| Khristian Dacanay Trading Ltd | Wholesale & retail | 2025 |
| Kilbegs Investment Co. Limited | Administrative & support | 1978 |
| Kilbrent Ltd | Professional & scientific | 2018 |
| Killycreen Limited | Financial services | 2023 |
| Killygarn Limited | Financial services | 2021 |
| Kinetic Martial Arts CIC | Education | 2023 |
| Kingdom Agape Ltd | Other services | 2025 |
| Kingsmore Group Ltd | Construction | 2023 |
| Kini Limited | Wholesale & retail | 2024 |
| Kinmore Consultancy Ltd | Professional & scientific | 2022 |
| Kirkpatrick Kitchens & Bedrooms Ltd | Manufacturing | 2017 |
| KISA2CARE Limited | Health & social care | 2022 |
| Klockner Moeller (Northern Ireland) Limited | | 1991 |
| KMI VA Solutions Limited | Health & social care | 2024 |
| Koopi Ltd | Information & communication | 2014 |
| Kronnos Technology Ltd | Wholesale & retail | 2022 |
| KUR Manufacturing Limited | Manufacturing | 2025 |
| L&S Painting Contractors Ltd | Construction | 2019 |
| LAD Electrics Ltd | Construction | 2024 |
| Ladc Properties Limited | Real estate | 2017 |
| Land Corp Property NO 2 Limited | Hospitality | 2023 |
| Lapis Training Solutions Ltd | Professional & scientific | 2023 |
| Largy Developments Limited | Real estate | 2017 |
| Larne Skip Hire Limited | Water & waste | 2021 |
| Laughter Land | Health & social care | 2005 |
| Lauren Mcateer Limited | Administrative & support | 2021 |
| Laurie MAC Interiors Ltd | Wholesale & retail | 2017 |
| LC Accountancy Services Ltd | Professional & scientific | 2025 |
| Learning Unlocked Ltd | Education | 2020 |
| Legal-Island Limited | Information & communication | 2013 |
| Lemaed Holdings Limited | Real estate | 2026 |
| Lenagh Properties Limited | Real estate | 2024 |
| Lens & Vision Limited | Wholesale & retail | 2020 |
| Lessabled Living Limited | Other services | 2010 |
| Lewis Cherry Limited | Professional & scientific | 2011 |
| Lifesciencehub UK Limited | Other services | 2011 |
| Lightworkni Ltd | Health & social care | 2019 |
| Linkubator Limited | Professional & scientific | 2004 |
| Lister Machine Tools (N.I.) Limited | Manufacturing | 1975 |
| Liston Locations Limited | Arts & recreation | 2016 |
| Little Izzies Ltd | Arts & recreation | 2024 |
| Lizdel Ltd | Health & social care | 2022 |
| LJ Catering Ltd | Hospitality | 2022 |
| Lmbr Company Ltd | Other services | 2026 |
| LMJ Commerce Ltd | Wholesale & retail | 2024 |
| Lnlm Properties Ltd | Financial services | 2026 |
| Lone Ridge Media Ltd | Information & communication | 2025 |
| Lough Bann Ltd | Construction | 2016 |
| Lough Contracts Ltd | Construction | 2025 |
| Loughbeg Motors Ltd | Wholesale & retail | 2022 |
| Loughbeg Torque Solutions Ltd | Manufacturing | 2024 |
| Lucky Charm Healthcare Limited | Health & social care | 2023 |
| Luke Smart Creative Ltd | Wholesale & retail | 2025 |
| Lumaet Ltd | Construction | 2025 |
| Lumen Electronics Ltd | Manufacturing | 2013 |
| LVY Contracts Ltd | Construction | 2013 |
| Lynco (UK) Limited | Construction | 2013 |
| Lynco Facades Limited | Construction | 2011 |
| Lynco Group Ltd. | Financial services | 2018 |
| Lynco Partitions & Cladding Ltd | Construction | 2012 |
| M & a Developments Ireland Ltd | Construction | 2007 |
| M & EM Properties Ltd | Real estate | 2024 |
| M & K Bros. Ltd | Construction | 2017 |
| M & S Connolly & Sons Ltd | Agriculture & fishing | 2010 |
| M Mcpeake Electrical Ltd | Construction | 2026 |
| M O'Kane Electrical Ltd | Manufacturing | 2012 |
| M REA & SON Limited | Wholesale & retail | 2018 |
| M&E Electrical (Belfast) Limited | Extraterritorial | 1975 |
| M&M Trailer Repairs Ltd | Manufacturing | 2026 |
| M&N Developments (N.I.) Limited | Construction | 2019 |
| M&N Properties (NI) Limited | Real estate | 2011 |
| M.S Roofing&Landscaping Limited | Construction | 2025 |
| M3 Entertainments Ltd | Hospitality | 2018 |
| M3 Fitout Limited | Construction | 2026 |
| MAC Red Developments Limited | Construction | 2020 |
| Mach Power Limited | Energy | 2013 |
| Machinefix Engineering Ltd | Other services | 2023 |