| Kilmoyle Farm Services Limited | Agriculture & fishing | 2016 |
| KNB Properties Ltd | Real estate | 2024 |
| Knock Hall Ltd | Financial services | 2023 |
| Knockeden Management Company Limited | Households | 2004 |
| Knocklayde Homes Ltd | Construction | 2019 |
| KP Moyan Ltd | Wholesale & retail | 2023 |
| Krafted by Victoria Ltd | Wholesale & retail | 2024 |
| KT Beauty Ltd | Other services | 2020 |
| LA Petite Baguette (NI) Ltd | Hospitality | 2026 |
| Lana Leisure Limited | Other services | 2019 |
| Landhead Power Ltd | Energy | 2012 |
| Langholm Operations Limited | Real estate | 1997 |
| Larmore Properties Limited | Real estate | 2006 |
| Leaf Asset Finance Limited | Financial services | 2024 |
| Leah the Confidence Coach Ltd | Arts & recreation | 2025 |
| Leon 4 Limited | Wholesale & retail | 2023 |
| Leslie & Leslie Limited | Professional & scientific | 2015 |
| Leumas Holdings Limited | Financial services | 2019 |
| Liberty Works Ltd. | Information & communication | 2014 |
| Lindka Limited | Hospitality | 2022 |
| Lislagan Solutions Ltd | Professional & scientific | 2020 |
| Little Lake Lodges Limited | Hospitality | 2021 |
| Little North Coast Tours Ltd | Transport & logistics | 2023 |
| Livery Farm Enterprises Limited | Agriculture & fishing | 2013 |
| Livery Hill Developments Ltd | Wholesale & retail | 2006 |
| LM Holdings Limited | Real estate | 2024 |
| LMK Lawyers Ltd | Professional & scientific | 2017 |
| Lovesticker Ltd | Manufacturing | 2017 |
| Lumos Management Limited | Financial services | 2023 |
| M Kane Contracts Ltd | Construction | 2011 |
| M.D.F. Electrical Limited | Construction | 2000 |
| MAC 13 Limited | Real estate | 2026 |
| Macey's Factory Limited | Manufacturing | 2023 |
| Maclogistics Ireland Limited | Transport & logistics | 2020 |
| MAF Plumbing and Heating Limited | Construction | 2022 |
| MAI Anna Nails & Beauty Ltd | Other services | 2026 |
| Maine DRY Lining Company Limited | Construction | 2000 |
| Manola Farm Supplies Limited | Manufacturing | 2003 |
| MAO Asian Ltd | Hospitality | 2018 |
| Mariano Investment Properties Limited | Real estate | 2016 |
| Markos Tech Solutions Ltd | Information & communication | 2020 |
| MC Comb Steel Ltd | Wholesale & retail | 2025 |
| MCA Properties Limited | Real estate | 1995 |
| Mcafee Properties Ltd | Real estate | 2003 |
| Mcauley Fabrication Limited | Manufacturing | 2013 |
| Mcauley FL Lifts Ltd | Manufacturing | 2018 |
| Mcauley Marketing Ltd | Professional & scientific | 2011 |
| Mcauley Precision Limited | Manufacturing | 2004 |
| Mccloskey Farms Ltd | Agriculture & fishing | 2012 |
| Mcclure Generating Ltd | Energy | 2014 |
| Mcconaghy Refrigerated Distribution Limited | Transport & logistics | 2014 |
| Mcguckian Brothers Ltd | Agriculture & fishing | 2017 |
| Mcilhatton & Co. Ltd | Manufacturing | 1990 |
| Mckillen Estates Ltd | Real estate | 2026 |
| Mckillen Holdings Ltd | Real estate | 2025 |
| MCL Metalworks Ltd | Manufacturing | 2026 |
| Mcmullan Turbines Ltd | Energy | 2013 |
| Megabites (Northern Ireland) Limited | Hospitality | 2003 |
| MET Construction Fixing's Ltd. | Wholesale & retail | 2017 |
| MID Tyrone Development Association Limited | Households | 1990 |
| Millbrae Cottage Nursery Limited | Wholesale & retail | 2015 |
| Millbrae Investment Properties Ltd | Real estate | 2022 |
| Millbrooke Services Ltd | Construction | 2025 |
| Millsport Motorcycles Ltd | Extraterritorial | 2024 |
| MMS Coaching Limited | Information & communication | 2023 |
| Mncc Properties Ltd | Real estate | 2020 |
| Moore (Unidrill) Limited | Wholesale & retail | 1974 |
| Moto Blast & Parts Refurb NI Ltd | Wholesale & retail | 2026 |
| Mountain Gold Limited | Manufacturing | 2010 |
| Moyle Construction Company Ltd | Construction | 2005 |
| MR Worx Ltd | Manufacturing | 2018 |
| Muhammad Labs Ltd | Information & communication | 2025 |
| Mulrose Developments Limited | Construction | 1995 |
| N Rays Ltd | Hospitality | 2024 |
| N.I. Computers Ltd | Wholesale & retail | 2025 |
| N.I.L.R.C. Ltd. | Arts & recreation | 2010 |
| NDR Transport Limited | Transport & logistics | 2017 |
| Necb Limited | Manufacturing | 2023 |
| NEX GEN Evolve Limited | Wholesale & retail | 2024 |
| Nicholl Holdings Limited | Construction | 2015 |
| Nicholls Hospitality&Catering Ltd | Hospitality | 2022 |
| NIS Contracts Ltd | Construction | 2023 |
| NO.13 Limited | Administrative & support | 2018 |
| Nobel Design Ltd | Wholesale & retail | 2017 |
| NOM Nomz UK Ltd | Manufacturing | 2016 |
| North Antrim Canines Ltd | Other services | 2025 |
| North Antrim Commercials Ltd | Wholesale & retail | 2024 |
| North Coast Engineering & SFX Ltd | Professional & scientific | 2025 |
| North Irish Horse Inn Ltd | Hospitality | 2024 |
| Northern Interior Fitouts Ltd | Construction | 2018 |
| Northern Worx Ltd | Real estate | 2023 |
| Northxsouth Limited | Wholesale & retail | 2016 |
| Novally Wind Ltd | Energy | 2016 |
| Novaro Styling Ltd | Wholesale & retail | 2025 |
| NT Rowles Ltd | Professional & scientific | 2025 |
| NW200 Assoc Limited | Other services | 2024 |
| O & C Builders Limited | Construction | 2017 |
| O'K Co Holdings Ltd | Financial services | 2023 |
| ON the North Coast Ltd | Hospitality | 2025 |
| Onyx N.Ireland Facilities Ltd | Wholesale & retail | 2024 |