| K'S Seated Activities Ltd | Health & social care | 2024 |
| K2 Cars Omagh (NI) Ltd | Wholesale & retail | 2021 |
| Kaison Ltd | Wholesale & retail | 2025 |
| Kaizen Print Ltd | Information & communication | 2014 |
| Kamas Limited | Real estate | 2003 |
| Karol Dolan Contracts Ltd | Construction | 2024 |
| Kaylon Design Limited | Construction | 2005 |
| KC Monaghan Construction Ltd | Construction | 2021 |
| KC Netting Limited | Construction | 2022 |
| Kcmcpgc Ltd | Financial services | 2025 |
| KDC & Sons Ltd | Construction | 2017 |
| KDM Consulting Ltd | Professional & scientific | 2023 |
| Kearney Steel Erecting Ltd | Construction | 2016 |
| KEE Civil Engineering Ltd | Construction | 2022 |
| Keen 2 Screen Ltd | Mining & quarrying | 2020 |
| Keenaghan Aggregates Limited | Mining & quarrying | 2013 |
| Keenan Engagement Ltd | Professional & scientific | 2026 |
| Keenogue Properties Ltd | Real estate | 2026 |
| Kegs 4 U Limited | Other services | 2012 |
| Kegs Direct Ireland Ltd | Other services | 2015 |
| KEL Trans Ltd | Transport & logistics | 2017 |
| Kelly Agri Contracts Ltd | Administrative & support | 2026 |
| Kelly Driver Hire Ltd | Transport & logistics | 2016 |
| Kelly Property Investments Ltd | Real estate | 2020 |
| Kelly Scaffolding Systems Ltd | Construction | 2025 |
| Kellycon Ltd | Administrative & support | 2019 |
| Kennedy Bacon Ltd | Manufacturing | 2016 |
| Kennedy Burchill Financial Ltd | Extraterritorial | 2025 |
| Kennedy Burchill Ltd | Other services | 2014 |
| Kennedy Independent Financial Advice Ltd | Financial services | 2010 |
| Kerr Bros Bodyshop Ltd | Wholesale & retail | 2014 |
| Kerr Farms Limited | Agriculture & fishing | 2013 |
| Kevlin Electrical Limited | Construction | 2012 |
| Kevlin Tyre and Service Centre Ltd | Wholesale & retail | 2021 |
| Keyes Brothers Construction Limited | Construction | 2000 |
| KF Enterprises Ltd | Wholesale & retail | 2024 |
| KG Building Services Consultant Ltd | Professional & scientific | 2020 |
| Khawer Ltd | Health & social care | 2015 |
| Kiddies Corner Ltd | Health & social care | 2024 |
| Kildrum Bar Ltd | Hospitality | 2023 |
| Kildrum Builders Ltd | Construction | 2015 |
| Killy Consultants Limited | Professional & scientific | 2018 |
| Killymeal Holdings Ltd | Professional & scientific | 2011 |
| Killynure Holdings Limited | Real estate | 2020 |
| Kilmore Consultancy Ltd | Professional & scientific | 2020 |
| Kilroe Ltd | Construction | 2019 |
| Kiltamnagh House Limited | Real estate | 2022 |
| Kiltamnagh Limited | Households | 2022 |
| Kinloch Property Holdings Ltd | Real estate | 2021 |
| Kirkland Auto Sales Ltd | Wholesale & retail | 2025 |
| KJ Supplies Ltd | Administrative & support | 2024 |
| KMA Trading & Investments Ltd | Professional & scientific | 2022 |
| KMG Farm Ltd | Agriculture & fishing | 2015 |
| KNA Window Blinds Ltd | Wholesale & retail | 2010 |
| Knockloe Properties Limited | Real estate | 2024 |
| Knockmoyle Lodge Care Facility Ltd | Health & social care | 2018 |
| Knocksilla Properties Limited | Real estate | 2021 |
| Kotc Events Ltd | Arts & recreation | 2022 |
| KP Civils (2024) Limited | Construction | 2024 |
| KP Properties (2024) Ltd | Real estate | 2026 |
| Krazy Kastles Ltd | Other services | 2012 |
| KRJ Property Investment Ltd | Real estate | 2025 |
| KS Farms Limited | Agriculture & fishing | 2013 |
| KSB Group Holdings Ltd | Financial services | 2021 |
| KSE IRL Ltd | Construction | 2020 |
| KSG Motors Ltd | Wholesale & retail | 2024 |
| Kwmj Holdings Limited | Financial services | 2024 |
| Kyle Donnelly Electrical Limited | Construction | 2021 |
| Kyle Smith Property Limited | Real estate | 2018 |
| L.A.S.T. Sure Start | Health & social care | 2005 |
| Lacomo Beauty Ltd | Wholesale & retail | 2012 |
| Lafayette Photography (NI) Limited | Professional & scientific | 2012 |
| Lagan Energy Engineering Limited | Construction | 2014 |
| Lagan Energy Hydrogen Development Limited | Professional & scientific | 2025 |
| Laganbank Limited | Real estate | 1998 |
| Lakemount Farms Limited | Agriculture & fishing | 2012 |
| Lakemount Holdings Ltd | Agriculture & fishing | 2023 |
| Lakeview Farm | Agriculture & fishing | 2025 |
| Lallyconsultancy Ltd | Professional & scientific | 2025 |
| Lamella Group Limited | Households | 2022 |
| Lana Mullan and Co T/A Lana & Co Ltd | Wholesale & retail | 2026 |
| Lancer Buildings Ltd | Real estate | 2000 |
| Land of Dream Bedding Limited | Wholesale & retail | 2015 |
| Landahussy Livestock Ltd | Agriculture & fishing | 2026 |
| Langlang Qiang Limited | Wholesale & retail | 2025 |
| Lantec Property Limited | Real estate | 2026 |
| Lappin Bros Ltd | Real estate | 2019 |
| Laragh Investments Limited | Real estate | 2026 |
| Laurence & Colette Mccann Ltd | Financial services | 2018 |
| Law by Lawri Limited | Information & communication | 2025 |
| Lawnakilla Ltd | Real estate | 2023 |
| LBN Foods Limited | Hospitality | 2022 |
| LCC Facilities Management Ltd | Real estate | 2016 |
| LCC Homecare Ltd | Health & social care | 2020 |
| LD2 Limited | Professional & scientific | 2004 |
| Leadership Conferencing Limited | Administrative & support | 2022 |
| Lecky Livestock Haulage Limited | Transport & logistics | 2020 |
| Lefty's Contracts Limited | Administrative & support | 2016 |
| Legcloughfin Farms Limited | Construction | 2014 |
| Legnashammer Holdings Limited | Financial services | 2022 |