| Kimran Energy Limited | Energy | 2015 |
| Kind Brav Ltd | Wholesale & retail | 2023 |
| Kindness of Strangers Claudy Ltd | Wholesale & retail | 2023 |
| Kindness of Strangers Cookstown Ltd | Wholesale & retail | 2021 |
| Kindness of Strangers Derry Ltd | Wholesale & retail | 2021 |
| Kindness of Strangers Limavady Ltd | Wholesale & retail | 2021 |
| King Solutions Ltd | Information & communication | 2023 |
| Kinship Care Northern Ireland Ltd | Health & social care | 2010 |
| Kippie C.I.C. | Education | 2016 |
| Kippie Games Ltd | Manufacturing | 2021 |
| Kirk (Seven) Management Company Ltd | Households | 2006 |
| KJL Properties Limited | Real estate | 2012 |
| Kkilkey Sales Ltd | Wholesale & retail | 2025 |
| Kllc Contracts Limited | Construction | 2011 |
| KM Legal Consultants Ltd | Administrative & support | 2012 |
| Kmac Drylining Ltd | Construction | 2025 |
| Kmac Northwest Limited | Wholesale & retail | 2014 |
| Kmccauley Transport Ltd | Manufacturing | 2018 |
| Kmcd Properties Ltd | Households | 2024 |
| Kmcf Properties Ltd | Real estate | 2021 |
| KMG Care Services Limited | Health & social care | 2024 |
| KMS Leak Detection Ltd | Construction | 2024 |
| Knectyr Ltd | Information & communication | 2026 |
| KON Construction Ltd | Construction | 2018 |
| Kool Kubes Ltd | Manufacturing | 2021 |
| KP O'Kane | Agriculture & fishing | 2010 |
| KP Street Food Ltd | Hospitality | 2019 |
| KPK Group Ltd | Construction | 2018 |
| KPS Nina Ltd | Health & social care | 2024 |
| KRD Promotions Ltd | Hospitality | 2023 |
| KRH Enterprises Limited | Construction | 2020 |
| KS Electrical Services Derry Limited | Construction | 2022 |
| KSB Investments Limited | Real estate | 2020 |
| Ksquare Seafoods Ltd | Wholesale & retail | 2020 |
| Kumi Trading Limited | Wholesale & retail | 2019 |
| Kurdish Barber Shop Ltd | Other services | 2024 |
| Kyrlin UK Ltd | Wholesale & retail | 2026 |
| L Hair & Beauty Ltd | Other services | 2018 |
| L M Plastering & Construction Limited | Construction | 2026 |
| L&J World Travel Ltd | Administrative & support | 2015 |
| L&S Private Ltd | Wholesale & retail | 2025 |
| L&T 24/7 Ltd | Wholesale & retail | 2023 |
| L.M. Touring Ltd | Arts & recreation | 2023 |
| L2WELD M.I.W.I Ltd | Construction | 2024 |
| Labh Developments Limited | Real estate | 2024 |
| LAC Wind Limited | Administrative & support | 2015 |
| Lacka Properties Limited | Real estate | 2002 |
| Lackagh Investments Ltd | Real estate | 2025 |
| Laco Ltd | Hospitality | 2001 |
| Ladbroke Projects Ltd | Real estate | 2022 |
| Ladymount Investments Limited | Real estate | 2016 |
| Lagan Press Limited | Information & communication | 1996 |
| Lagavara Limited | Construction | 2011 |
| Lagenod Investments Limited | Real estate | 2015 |
| Lancaster Projects Ltd | Real estate | 2017 |
| Lanta Foods Limited | Hospitality | 2021 |
| Larbert Ltd | Construction | 2020 |
| Larkheight Properties Limited | Real estate | 2007 |
| Laundry World Ltd | Other services | 2022 |
| Laurence's Loft Ltd | Hospitality | 2016 |
| LBC Retail Limited | Wholesale & retail | 2026 |
| Lcma Hotels Ltd | Hospitality | 2014 |
| LD Project Management Limited | Professional & scientific | 2015 |
| LDK Engineering Ltd | Professional & scientific | 2025 |
| LE Gazpi Holdings Ltd | Financial services | 2024 |
| Leadcare Nursing Agency Ltd | Administrative & support | 2020 |
| Leadcare Recruitment Limited | Administrative & support | 2024 |
| Lear Mechanical Services Ltd | Construction | 2013 |
| Leard Future Limited | Wholesale & retail | 2026 |
| Learning Solutions Ltd | Information & communication | 2022 |
| Leckpatrick Dairies Limited | Wholesale & retail | 1989 |
| Leckpatrick Holdings Limited | Professional & scientific | 1989 |
| Legacy Promotions Iona Ltd | Arts & recreation | 2014 |
| Legavallon Properties Limited | Real estate | 2025 |
| Legenderry AB Ltd | Wholesale & retail | 2019 |
| Legenderry Brewing Company Limited | Manufacturing | 2014 |
| Legenderry Hospitality Limited | Hospitality | 2023 |
| Legenderry Properties Ltd | Real estate | 2024 |
| Leighton Consultancy NI Limited | Professional & scientific | 2009 |
| Leisure Ireland Ltd. | Hospitality | 2011 |
| Leitir Tunnelling Limited | Construction | 2016 |
| Lemon Communications (NI) Ltd | Extraterritorial | 2007 |
| Lemongrass BT47 Limited | Hospitality | 2026 |
| Lenamore Enterprises Ltd | Professional & scientific | 2026 |
| Lesge Grpo Ltd | Wholesale & retail | 2024 |
| Letor Limited | Agriculture & fishing | 2012 |
| Levelheaded Tech Limited | Information & communication | 2016 |
| Lewis Fastravel Limited | Administrative & support | 1969 |
| Lewispark Properties Ltd | Real estate | 2016 |
| Lexus Projects Limited | Real estate | 2018 |
| Liam Barr Electrical Limited | Construction | 2024 |
| Liberty Bridge Car Sales Limited | Wholesale & retail | 2019 |
| Liberty Contracts Ltd | Water & waste | 2009 |
| Libhar Holdings Limited | Professional & scientific | 2018 |
| Lifecellsni Limited | Professional & scientific | 2022 |
| Lifestart Resources Ltd | Information & communication | 2014 |
| Lighting Concepts Ltd | Wholesale & retail | 2020 |
| Limavady Concrete Products Ltd | Manufacturing | 2015 |
| Limavady Turkish Barbers Ltd | Other services | 2025 |
| Lime Road Productions Ltd | Information & communication | 2019 |