| KES Attachments Limited | Manufacturing | 2023 |
| Kesh Wind Ltd | Energy | 2016 |
| Kestutis Kvietkauskas Limited | Wholesale & retail | 2022 |
| Kettle and Ward Physiotherapy and Sports Massage Ltd | Public administration | 2025 |
| Kevin Cartin Architects Limited | Professional & scientific | 2006 |
| Kevin Glass Ltd | Wholesale & retail | 2025 |
| Kevin Mcshane Ltd | Professional & scientific | 2014 |
| Kevin Watson Group Limited | Professional & scientific | 2014 |
| Kevin Whisper Ltd | Wholesale & retail | 2024 |
| Kevo (2015) Limited | Construction | 2014 |
| Key IS Key Tech Ltd | Wholesale & retail | 2024 |
| Key One Property Ltd | Real estate | 2012 |
| Keyabange Trade Limited | Wholesale & retail | 2024 |
| Keys 7KS Limited | Health & social care | 2011 |
| Keys Care Limited | Health & social care | 2004 |
| Keys Education & Care Limited | Health & social care | 2010 |
| Keys Financial Services Limited | Financial services | 1982 |
| Keys Premium Finance (2001) Limited | Financial services | 2001 |
| Keys Premium Finance (2006) Ltd | Financial services | 2006 |
| Keys Premium Finance Limited | Financial services | 1996 |
| Keysmart Limited | Administrative & support | 2016 |
| Keystone Properties (Belfast) Limited | Real estate | 2000 |
| Keziban Home Furnishing Limited | Wholesale & retail | 2024 |
| KFD Power Limited | Wholesale & retail | 2025 |
| KGB Alarms Limited | Construction | 2010 |
| Kgbr Limited | Extraterritorial | 2019 |
| KGG Partners Limited | Wholesale & retail | 2020 |
| KGJ Developments Ltd | Real estate | 2024 |
| Kgjbzn Limited | Wholesale & retail | 2024 |
| Kgram Design Ltd | Professional & scientific | 2016 |
| Kgsb Project Management Limited | Construction | 2008 |
| KGT Builders Limited | Construction | 2023 |
| KGT Electrical & Building Solutions Limited | Construction | 2013 |
| KH 2020 Limited | Financial services | 1998 |
| KH Cosmetics Limited | Wholesale & retail | 2025 |
| KH Management Services Limited | Real estate | 2020 |
| Khaled Ltd | Construction | 2025 |
| Khamo Certification Ltd | Administrative & support | 2026 |
| Khara Pringle Photography Ltd | Information & communication | 2014 |
| KHB Deli House Ltd | Hospitality | 2025 |
| KHM Hair Limited | Other services | 2025 |
| KHP Services Ltd | Information & communication | 2025 |
| KHT+ Ltd | Real estate | 2025 |
| Khursheed Ltd | Health & social care | 2018 |
| Khyber Spice 2004 Ltd | Hospitality | 2024 |
| Kibni Limited | Financial services | 2020 |
| Kick Logistics Limited | Professional & scientific | 2021 |
| Kickz Fresh Ltd | Wholesale & retail | 2025 |
| Kicteam Europe Limited | Administrative & support | 2009 |
| Kiddies Kabin Ltd | Wholesale & retail | 2017 |
| Kiddynet Ltd | Manufacturing | 2011 |
| Kidi Express Ltd | Hospitality | 2020 |
| Kids in Control | Arts & recreation | 1997 |
| Kids Korner Day Nurseries Ltd | Health & social care | 2007 |
| Kids of Mine Ltd | Wholesale & retail | 2018 |
| Kids Play DEN (NI) Ltd | Health & social care | 2012 |
| Kids Road Wind Ltd | Energy | 2016 |
| Kids Together Belfast | Administrative & support | 2019 |
| Kiemail Ltd | Administrative & support | 2022 |
| Kieran Mccann Limited | Wholesale & retail | 2025 |
| Kieran Sky Ltd | Administrative & support | 2025 |
| Kieranbullion Limited | Wholesale & retail | 2025 |
| Kiez (Merchant Building) Limited | Real estate | 2023 |
| Kiez 2017 Limited | Real estate | 2017 |
| Kiez Edinburgh Limited | Real estate | 2017 |
| Kiez Healthcare Limited | Administrative & support | 2017 |
| Kiez Property Limited | Households | 2006 |
| Kiki 24 Ltd | Hospitality | 2024 |
| Kiki African Store Ltd | Wholesale & retail | 2025 |
| Kilbor Holdings Limited | Financial services | 2016 |
| Kilcad Properties Limited | Construction | 2015 |
| Kilcooley Social Economy Hub CIC | Construction | 2020 |
| Kilhorne Bay Seafoods Limited | Manufacturing | 1970 |
| Killagan Holdings Limited | Financial services | 2018 |
| Killagan Limited | Administrative & support | 2010 |
| Killaghtee Property Limited | Extraterritorial | 2018 |
| Killane Management Company Limited | Households | 2006 |
| Killaughey Homes Ltd | Construction | 2015 |
| Killead Airlodge Ltd | Wholesale & retail | 2025 |
| Killowen Holdings Ltd | Professional & scientific | 2018 |
| Killultagh Developments Limited | Real estate | 2020 |
| Killultagh Estates Limited | Real estate | 2015 |
| Killultagh Holdings Limited | Financial services | 2015 |
| Killultagh Investments Limited | Real estate | 2020 |
| Killultagh Mercantile Holdings Limited | Construction | 2019 |
| Killultagh Mercantile Limited | Construction | 2018 |
| Killultagh NI Limited | Real estate | 2020 |
| Killultagh Projects Limited | Construction | 2006 |
| Killultagh Properties Limited | Real estate | 1995 |
| Killvallon Limited | Real estate | 2012 |
| Killybeg West Wind Ltd | Energy | 2016 |
| Killybrack Management Limited | Households | 2015 |
| Killybrack Meadows Management Company Limited | Households | 2025 |
| Killygoan Rams Holdings Limited | Financial services | 2025 |
| Killyleagh Box Co.Limited | Manufacturing | 1980 |
| Killylodge Holdings Limited | Financial services | 2023 |
| Killymaddy Hill Management Company Ltd | Real estate | 2016 |
| Killyrudden Wind Ltd | Energy | 2016 |
| Kilmeaden Foods NI Limited | Wholesale & retail | 1981 |
| Kilminiogue Ltd | Professional & scientific | 2011 |