| K-Tec Engineering Ltd | Manufacturing | 2018 |
| Kamar North Trading Limited | Professional & scientific | 2026 |
| KBP Printing Company Ltd | Manufacturing | 2018 |
| KE Holdings Group Limited | Financial services | 2025 |
| KE Holdings Ltd | Administrative & support | 2016 |
| KE Plumbing Supplies Ltd | Wholesale & retail | 2006 |
| Keeranbeg Wind Ltd | Energy | 2014 |
| Keldev 2 Ltd | Real estate | 2026 |
| Keldev Ltd | Construction | 2026 |
| Kelly & O'Neill Ltd | Professional & scientific | 2010 |
| Kelso Car Sales Limited | Wholesale & retail | 2013 |
| Kestrel Hydraulics Limited | Manufacturing | 1989 |
| Keyfix Limited | Manufacturing | 2019 |
| Keylite Holding Ltd | Professional & scientific | 2013 |
| Keylite Roof Windows Limited | Manufacturing | 1999 |
| Keysip Limited | Extraterritorial | 2010 |
| Keystone Holding Ltd | Professional & scientific | 2013 |
| Keystone Lintels Limited | Manufacturing | 1988 |
| Keywall Limited | Manufacturing | 2022 |
| Kgss Limited | Professional & scientific | 2015 |
| KH Farms (N.I.) Ltd | Agriculture & fishing | 2016 |
| KH Group Investments Ltd | Financial services | 2024 |
| KHA Enterprises Ltd | Real estate | 2025 |
| Kilbrae Furniture Limited | Manufacturing | 2002 |
| Kildress Holdings Limited | Financial services | 2024 |
| Kildress Joinery Limited | Manufacturing | 2008 |
| Killygore Wind Ltd | Energy | 2013 |
| Kiloutou (N.I) Limited | Financial services | 2026 |
| Kindle Occasions Limited | Wholesale & retail | 2019 |
| Kinler Developments Limited | Construction | 2024 |
| Kintone Limited | Agriculture & fishing | 2007 |
| Kinturk Cultural Centre Ltd | Arts & recreation | 1994 |
| KMH Installations Ltd | Construction | 2015 |
| KMV Civils Ltd | Construction | 2025 |
| Knockaconny Catering Ltd | Hospitality | 2026 |
| Known Marketing Agency Ltd | Professional & scientific | 2025 |
| Kosy Coal Ltd | Wholesale & retail | 2009 |
| Kpni Ltd | Extraterritorial | 1993 |
| KS Treasury Limited | Professional & scientific | 2019 |
| Kurate Holdings Ltd | Financial services | 2016 |
| Kurate International Ltd | Wholesale & retail | 2003 |
| Kurate Investments Ltd | Real estate | 2016 |
| L Loughran & Sons Contracts Ltd | Construction | 2016 |
| L M Farm Ltd | Wholesale & retail | 2016 |
| Lady L Ltd | Wholesale & retail | 2017 |
| LCC Coatings Ltd | Manufacturing | 2024 |
| LCC Enterprises Ltd | Real estate | 2018 |
| LCC Group Holdings Ltd | Financial services | 2018 |
| LCC Power Limited | Energy | 2011 |
| LCC Properties & Investments Ltd | Real estate | 2019 |
| LCC Trading & Minerals Ltd | Wholesale & retail | 2019 |
| LD Farm Ltd | Agriculture & fishing | 2013 |
| LDC Corporate Holdings Ltd | Financial services | 2025 |
| LDC Electrics Ltd | Construction | 2018 |
| LDC Property Investments Ltd | Real estate | 2025 |
| LDL Aggregates Ltd | Mining & quarrying | 2011 |
| Leadon Holdings Ltd | Financial services | 2024 |
| Leadon Properties Ltd | Real estate | 2024 |
| Liberty Church Mid-Ulster | Education | 2021 |
| Life Time Enterprises PVT Ltd | Wholesale & retail | 2024 |
| Lilac Cancer Support Ltd | Health & social care | 2011 |
| Limavady Bess Ltd | Energy | 2023 |
| Lindview Limited | Construction | 2011 |
| Liskeeran Donegal Wind Ltd | Energy | 2016 |
| Lisnamuck Design & Consultancy Limited | Professional & scientific | 2012 |
| Lissan Hall Committee Limited | Administrative & support | 2017 |
| Lissan House Trust | Arts & recreation | 1997 |
| LJD Homes Ltd | Real estate | 2020 |
| Loch Rainbow Fisheries Limited | Hospitality | 1984 |
| Lough Neagh Stays Ltd | Hospitality | 2026 |
| Loughdoo Aggregates & Concrete (Ballymena) Ltd | Mining & quarrying | 2011 |
| Loughdoo Joinery & Building Contractors Ltd | Construction | 2003 |
| Loughloughan Wind Ltd | Energy | 2013 |
| Loughran Bulk Transport Limited | Transport & logistics | 2011 |
| Loughran Commercial Repairs Ltd | Wholesale & retail | 2020 |
| Loughran Commercials Ltd | Administrative & support | 2012 |
| Loughshore Community Services | Arts & recreation | 2015 |
| Loughshore Logistics Ltd | Transport & logistics | 2023 |
| Loughview Eggs Ltd | Agriculture & fishing | 2024 |
| LOW LOW Renewables Limited | Professional & scientific | 2017 |
| LOW LOW Utilities Limited | Professional & scientific | 2017 |
| Lowborn Theatre Company Ltd | Arts & recreation | 2024 |
| Lower Retreat Management Company Ltd | Administrative & support | 2020 |
| LOY Developments Ltd | Real estate | 2015 |
| Lurganmore Wind Farm Limited | Energy | 2021 |
| M & a Associates Limited | Real estate | 2008 |
| M & M Refractories Limited | Manufacturing | 2016 |
| M and K Bell Limited | Extraterritorial | 2013 |
| M&Mss Ltd | Administrative & support | 2026 |
| M&Rp Holdings Limited | Financial services | 2018 |
| M.R Motor Sales Ltd | Wholesale & retail | 2019 |
| Mabocu Ltd | Arts & recreation | 2025 |
| MAC Developers Limited | Extraterritorial | 2004 |
| MAC Electrical Wholesale Limited | Wholesale & retail | 2014 |
| Macm (NI) Ltd | Construction | 2012 |
| Magherakeel Wind Farm Limited | Energy | 2018 |
| Magic INK Ltd | Arts & recreation | 2018 |
| Mairon Ltd | Administrative & support | 2018 |
| MAK Fastener Specialists (NI) Limited | Wholesale & retail | 2001 |
| Malcolm Henry & Sons Farm Ltd | Agriculture & fishing | 2026 |