| Joy Avenue Ltd | Arts & recreation | 2025 |
| JP & S Construction Limited | Construction | 2018 |
| JP & S Hire Limited | Administrative & support | 2023 |
| JP Mcdonald Construction Ltd | Construction | 2010 |
| JPD Motors Ltd | Wholesale & retail | 2025 |
| JPK Contract Services Ltd | Construction | 2017 |
| JRS Commercials and Cars Ltd. | Wholesale & retail | 2013 |
| Jslg Property Ltd | Real estate | 2022 |
| JSM Commercial & Industrial Cleaners Ltd | Administrative & support | 2017 |
| JT Beeswing Ltd | Transport & logistics | 2022 |
| JT Online Trading Ltd | Wholesale & retail | 2022 |
| JT Plant Sales & Hire Ltd | Wholesale & retail | 2020 |
| Just Digit (2016) Ltd | Construction | 2016 |
| Just Start Fitness Ltd | Arts & recreation | 2020 |
| K and T Solutions Ltd | Financial services | 2023 |
| K Hughes Contracts Ltd | Construction | 2021 |
| K Hughes Estates Ltd | Real estate | 2016 |
| K&C Scullion Ltd | Agriculture & fishing | 2005 |
| K&K MOY Properties Limited | Real estate | 2022 |
| K-Scaff Ltd | Wholesale & retail | 2016 |
| Kadaf Ltd | Professional & scientific | 2021 |
| Kane Holdings Ltd | Real estate | 2023 |
| Kanes Construction Limited | Construction | 2004 |
| Kanes Holding Ltd | Construction | 2025 |
| KC Matthews Ltd | Wholesale & retail | 2023 |
| KC Organisation Ltd | Real estate | 2017 |
| KC Property Ltd | Real estate | 2015 |
| KC2025 Ltd | Hospitality | 2025 |
| KCE Comms Ltd | Information & communication | 2019 |
| KDL Property Ltd | Real estate | 2015 |
| KDL Scaffolding & Access Ltd | Construction | 2014 |
| Kearney Transport Ltd | Transport & logistics | 2010 |
| KEE Architecture Ltd | Professional & scientific | 2009 |
| Keenaghan Mushrooms Ltd | Agriculture & fishing | 2012 |
| Keep Books Limited | Professional & scientific | 2021 |
| Kelcom Ltd | Construction | 2022 |
| Kelgar Limited | Wholesale & retail | 2010 |
| Kelgar Logistics Ltd | Transport & logistics | 2010 |
| Kelgar Transport Ltd | Transport & logistics | 2011 |
| Kellenergy Limited | Energy | 2016 |
| Kelly Mechanical Services (NI) Ltd | Construction | 2020 |
| Kelpro Limited | Real estate | 2023 |
| KEM Construction Ltd | Construction | 2023 |
| Kenneth Irwin & Sons Limited | Professional & scientific | 2006 |
| Kenzoku Digital Ltd | Information & communication | 2024 |
| Kermac Properties Limited | Professional & scientific | 2007 |
| Kerr Electrical Ltd | Construction | 2020 |
| Kerrib Consultancy Ltd | Real estate | 2022 |
| Kerrib Holding Co. Ltd | Health & social care | 2016 |
| Kevack Transport Ltd | Transport & logistics | 2024 |
| Kevin Barrys Production Services Ltd | Construction | 2026 |
| Key Turn Services Ltd | Administrative & support | 2026 |
| Keytec Waterproofing Ltd | Construction | 2007 |
| KFL Food Group Ltd | Hospitality | 2025 |
| KG Truck and Plant Ltd | Manufacturing | 2026 |
| Kick Consulting Ltd | Professional & scientific | 2003 |
| Kiddiwinkles Care and Learning Centre Limited | Health & social care | 2014 |
| Kids and Bibs Daycare Ltd | Health & social care | 2012 |
| Kids Zone Adventure Soft Play Ltd | Arts & recreation | 2026 |
| Killen Commercial Ltd | Construction | 2015 |
| Killen Developments Ltd | Construction | 2015 |
| Killybracken Farms Ltd | Agriculture & fishing | 2015 |
| Killycolpy Consultants Ltd | Information & communication | 2026 |
| Killygarvan Pharma Services Ltd | Wholesale & retail | 2014 |
| Killygarvin Farm Eggs Ltd | Agriculture & fishing | 2016 |
| Killyliss Eglish Management Limited | Construction | 2010 |
| Killymaddy Holdings Ltd | Manufacturing | 2018 |
| Killyneill Enterprises Limited | Real estate | 1998 |
| Kilmore Civils Limited | Construction | 2016 |
| Kilmore Homes Limited | Construction | 2019 |
| Kilmore Plant Limited | Administrative & support | 2020 |
| Kilmore Trading Ltd | Wholesale & retail | 2011 |
| Kilnaslee Pigs Limited | Agriculture & fishing | 2014 |
| Kilpatrick Holdings Limited | Real estate | 2018 |
| Kilsannagh Mushrooms Ltd. | Agriculture & fishing | 2013 |
| Kinchul Ltd | Wholesale & retail | 2025 |
| Kinler Properties Limited | Real estate | 2000 |
| Kinora Estates Limited | Real estate | 2021 |
| Kinora Investments Limited | Financial services | 2018 |
| Kinora Properties Limited | Real estate | 2020 |
| Kinora Storage (NI) Property NO1 Ltd | Real estate | 2022 |
| Kinora Storage (NI) Trading Ltd | Administrative & support | 2022 |
| Kinrush Project Specialists Limited | Administrative & support | 2023 |
| Kirkland Farms Ltd | Agriculture & fishing | 2013 |
| Kirkland Fuels Limited | Other services | 2007 |
| Kiverco Recycling Plant Ltd | Manufacturing | 2015 |
| Kivermac Limited | Financial services | 2023 |
| KJT Limited | Real estate | 2021 |
| KK Developments Limited | Construction | 1999 |
| KM Financial Ltd | Professional & scientific | 2021 |
| KMC Supplies Limited | Manufacturing | 2004 |
| KMC Transport Ltd | Transport & logistics | 2019 |
| KMC Works Limited | Manufacturing | 2022 |
| KMK Property Group Ltd | Extraterritorial | 2024 |
| Kmki Engineering NI Ltd | Manufacturing | 2023 |
| KMR Kawasaki Ltd | Arts & recreation | 2012 |
| KMS Hire Ltd | Administrative & support | 2021 |
| Knife Edge Outdoor Limited | Information & communication | 2017 |
| Knockburn Limited | Construction | 2012 |
| Knox Poultry Sales Limited | Agriculture & fishing | 2018 |