| Jollyion Ltd | Wholesale & retail | 2025 |
| Jonzara Holdings Ltd | Financial services | 2024 |
| Jonzara Lisburn Limited | Wholesale & retail | 2016 |
| Jonzara Ltd | Wholesale & retail | 2008 |
| Jonzara Newtownards Limited | Wholesale & retail | 2018 |
| Jordan Campbell Ltd | Wholesale & retail | 2025 |
| Jordan's Court Management Limited | Households | 2023 |
| JP & Sons Contracts Ltd | Construction | 2023 |
| JP Drone Survey Solutions Ltd | Professional & scientific | 2024 |
| Jpooii Ltd | Wholesale & retail | 2025 |
| Jprc Fitness Ltd | Arts & recreation | 2025 |
| JRG Services Limited | Professional & scientific | 2024 |
| JS Multisports Ltd | Education | 2024 |
| JS Plaice 777 Limited | Hospitality | 2026 |
| JSM Farming Ltd | Agriculture & fishing | 2021 |
| JSW Developments Ltd | Construction | 2012 |
| JSW Flooring Solutions Ltd | Construction | 2018 |
| JTF Aerostructures Ltd | Manufacturing | 2018 |
| Jubilee Property (Newtownards) Ltd | Real estate | 2022 |
| Jubilee Veterinary Centre Limited | Professional & scientific | 2011 |
| Jule Holdings Ltd | Hospitality | 2025 |
| JULESRIDING110 Ltd | Wholesale & retail | 2024 |
| Julian Sharp Limited | Wholesale & retail | 2025 |
| Jumfox Limited | Wholesale & retail | 2024 |
| June Burgess Ltd | Other services | 2015 |
| Juno Information Security Ltd | Information & communication | 2024 |
| Just Relax Properties Ltd | Real estate | 2016 |
| Justure Technology Hongkong Limited | Wholesale & retail | 2025 |
| JWK Property Ltd | Real estate | 2026 |
| JWL Group Ltd | Information & communication | 2021 |
| Jwnoon Business Ltd | Wholesale & retail | 2024 |
| JY Property Management Limited | Real estate | 2017 |
| K R Property Maintenance Ltd | Real estate | 2024 |
| K&H Group Ltd | Hospitality | 2021 |
| K2 Squared Ltd | Health & social care | 2023 |
| Kaimitdin Limited | Wholesale & retail | 2025 |
| Kairos Property Ltd | Real estate | 2024 |
| Kaixing Limited | Wholesale & retail | 2025 |
| Kaleston Consultancy Limited | Administrative & support | 2024 |
| Kalet Shop Limited | Wholesale & retail | 2025 |
| Kamca SOY Limited | Wholesale & retail | 2025 |
| Kamil Iyas Ltd | Wholesale & retail | 2024 |
| Kane Engineering Limited | Manufacturing | 1971 |
| Kane Financial Services Limited | Financial services | 1989 |
| Karim EON Limited | Wholesale & retail | 2024 |
| Katen Spares Limited | Wholesale & retail | 2024 |
| Katyut Trading Limited | Wholesale & retail | 2025 |
| Kech Kreations Ltd | Administrative & support | 2022 |
| Keeptired Ltd | Wholesale & retail | 2025 |
| Kell EAN Chemicals Ltd | Wholesale & retail | 2023 |
| Kelleman Enterprises Ltd | Hospitality | 2013 |
| Kellyskidz Ltd | Health & social care | 2024 |
| Kemon (N.I.) Limited | Wholesale & retail | 2018 |
| Kendal Agencies (Ingredients) Ltd | Hospitality | 2005 |
| Kengrapp Pro Limited | Wholesale & retail | 2025 |
| Keydew Properties Limited | Construction | 2007 |
| Keypoint Growth Ltd | Wholesale & retail | 2024 |
| Keystaff (N.I.) Ltd | Administrative & support | 2018 |
| Keystone Building Surveying Limited | Professional & scientific | 2023 |
| Kfly Louner Ltd | Wholesale & retail | 2023 |
| KG Accessories UK Limited | Wholesale & retail | 2015 |
| Khando Industries Ltd | Professional & scientific | 2019 |
| Kidogo Kids | Other services | 2019 |
| Kilarn Holdings Limited | Financial services | 2022 |
| Kilbright Farming Ltd | Agriculture & fishing | 2017 |
| Killaire Agencies Ltd | Wholesale & retail | 2010 |
| Killinchy Activity Group Open Centre C.I.C. | Education | 2025 |
| Killinchy and District Community Development Association Limited | Arts & recreation | 2000 |
| Killinchy Contracts Ltd | Administrative & support | 2010 |
| Killinchy Free Range Pork Limited | Agriculture & fishing | 2017 |
| Killinchy Meats Ltd | Wholesale & retail | 2013 |
| Killinchy Plumbing & Heating Ltd | Construction | 2026 |
| Killyleagh Football Club | Arts & recreation | 2013 |
| Killymaddye Grove Management Company Limited | Households | 2007 |
| Kiltonga Christian Centre Limited | Health & social care | 2009 |
| Kilwarlin Joinery Design & Build Ltd | Construction | 2010 |
| Kimberly Espinel Limited | Wholesale & retail | 2025 |
| Kinley Leisure Ltd | Hospitality | 2025 |
| Kircubbin Properties Limited | Wholesale & retail | 1978 |
| Kircubbin Regeneration Programme | Real estate | 2005 |
| Kirils Sakels Limited | Wholesale & retail | 2025 |
| Kirk Contracts (N.I.) Ltd | Construction | 2020 |
| Kirk Mcdermott Consulting Limited | Construction | 2016 |
| Kirstiejaynede Limited | Wholesale & retail | 2024 |
| Kitchens by Kelly Ltd | Manufacturing | 2021 |
| Kitchens by Kilwarlin Ltd | Manufacturing | 2021 |
| Kitlas Cosmetics Ltd | Wholesale & retail | 2025 |
| KM INK Limited | Other services | 2024 |
| KME Trading Ltd | Arts & recreation | 2024 |
| Kmoon Shop Limited | Wholesale & retail | 2025 |
| Knilahte Limited | Wholesale & retail | 2025 |
| Knock Motor Cycle and Car Club Limited | Arts & recreation | 1929 |
| Knockbracken Gardens Property Management Company Limited | Households | 2020 |
| Knockhill Court Management Ltd | Households | 2011 |
| Knocklayd Limited | Information & communication | 2011 |
| Knocknatten Developments Limited | Construction | 2016 |
| Knotts Bakery Holdings Limited | Financial services | 2016 |
| Knotts Bakery Limited | Hospitality | 2009 |
| Knowe Farm Consultancy Ltd | Professional & scientific | 2024 |
| Kobe Sports Limited | Wholesale & retail | 2024 |