| Just in Case HQ Ltd | Information & communication | 2026 |
| Just Indian Limited | Hospitality | 2018 |
| Just Learning Ateneo: Labour History, Co-Operation and Heritage Ltd | Education | 2023 |
| Just Lite Creative Ltd | Administrative & support | 2017 |
| Just Mist Wholesale Ltd | Wholesale & retail | 2016 |
| Just Reliable International Ltd | Wholesale & retail | 2025 |
| Just Tanker Services UK Limited | Administrative & support | 2022 |
| Just Write Marketing Ltd | Information & communication | 2021 |
| Justar Technology Limited | Wholesale & retail | 2025 |
| Justro Properties Ltd | Real estate | 2010 |
| JW & J Porter Limited | Construction | 2015 |
| JW Life Sciences Limited | Wholesale & retail | 2026 |
| JW NI Property Ltd | Real estate | 2023 |
| JW Orthopaedics Ltd | Health & social care | 2026 |
| JW Rigs Ltd | Construction | 2023 |
| JWL Mechanical Ltd | Construction | 2026 |
| Jxhuang Limited | Wholesale & retail | 2023 |
| JY 81 Ltd | Hospitality | 2026 |
| Jyde BEE Ltd | Extraterritorial | 2024 |
| K & D Catering (2020) Ltd | Hospitality | 2020 |
| K & E Whitson Ltd | Wholesale & retail | 2016 |
| K & F Industries Limited | Financial services | 2012 |
| K & R Event Catering Limited | Hospitality | 2023 |
| K and Jays Limited | Health & social care | 2023 |
| K Bedding NI Limited | Wholesale & retail | 2020 |
| K Contracts Limited | Manufacturing | 2008 |
| K Copeland Hair School Limited | Education | 2015 |
| K D Casa Ltd | Real estate | 2015 |
| K E-H Medical Ltd | Health & social care | 2025 |
| K Hamilton Contracts Ltd | Construction | 2019 |
| K Investment Holdings Ltd | Financial services | 2024 |
| K J Andrew Consulting Ltd | Professional & scientific | 2024 |
| K K Customs Ltd | Manufacturing | 2025 |
| K Rooney Contracts Limited | Construction | 2010 |
| K S Mallon Retail Ltd | Wholesale & retail | 2020 |
| K&K Media LP | | 2025 |
| K&M Properties Limited | Real estate | 2013 |
| K&M Technical Services Ltd | Professional & scientific | 2011 |
| K&R Group Holdings Limited | Hospitality | 2025 |
| K-Yuan Trading Limited | Wholesale & retail | 2025 |
| K.A.R Auto Repair's Ltd | Wholesale & retail | 2020 |
| K.E.M U.K. Ltd | Construction | 2017 |
| K.I.S.S Sports Fuel Ltd | Manufacturing | 2025 |
| K.M.W.N.I. Limited | Real estate | 2022 |
| K2 Medical Care Ltd | Health & social care | 2020 |
| K3 Trade Ltd | Wholesale & retail | 2024 |
| K35 Limited | Arts & recreation | 2019 |
| K4 Civils Ltd | Construction | 2016 |
| K9 Clubhouse Ltd | Other services | 2024 |
| KA Engineering Group Ltd | Professional & scientific | 2018 |
| KA LAI International Limited | Wholesale & retail | 2025 |
| KA Software Solutions Limited | Information & communication | 2015 |
| KA Weng International Trading Limited | Wholesale & retail | 2025 |
| Ka-Boom Films Limited | Manufacturing | 2014 |
| Ka-Boom Productions Limited | Information & communication | 2010 |
| Kaaima Limited | Real estate | 2019 |
| KAB 12 Ltd | Administrative & support | 2022 |
| KAB Holdings Limited | Financial services | 2024 |
| Kabosh | Arts & recreation | 1995 |
| Kacpz Pczak Ltd | Wholesale & retail | 2024 |
| Kaffe O 2 Limited | Hospitality | 2020 |
| Kaffe O Ltd | Hospitality | 2014 |
| Kaffe O Wholesale Ltd | Wholesale & retail | 2015 |
| Kafka Brigade UK and Ireland Ltd | Other services | 2011 |
| Kagisano Healthcare Ltd | Health & social care | 2022 |
| KAI KAI Johnson Ltd | Wholesale & retail | 2021 |
| Kainos Evolve Limited | Information & communication | 2014 |
| Kainos Products Limited | Information & communication | 2025 |
| Kainos Software Limited | Information & communication | 1986 |
| Kainos Trustees Limited | Administrative & support | 2000 |
| Kainos Worksmart Limited | Information & communication | 2014 |
| Kainoz Software Solutions Limited | Information & communication | 2019 |
| Kaira Investment Company | Financial services | 2026 |
| Kairos Sports Tech Ltd | Information & communication | 2018 |
| Kaitze Industry Company Limited | Wholesale & retail | 2024 |
| Kaizen Online Coaching Ltd | Other services | 2021 |
| Kaizen Safeguarding Limited | Professional & scientific | 2026 |
| Kaizen Strength Ltd | Arts & recreation | 2019 |
| Kaizen Training Academy Limited | Education | 2019 |
| Kaizenhub Technologies Limited | Information & communication | 2025 |
| KAK Properties Ltd | Real estate | 2016 |
| Kalakeli Ltd | Administrative & support | 2025 |
| Kaleidoscope C.I.C. | Arts & recreation | 2006 |
| Kalevala Bay LP | | 2016 |
| Kali Belfast Holdco Limited | Professional & scientific | 2021 |
| Kali Belfast Limited | Real estate | 2014 |
| Kali Propco Limited | Construction | 2021 |
| Kaluna Therapies Ltd | Other services | 2022 |
| Kalyas Steel Ltd | Manufacturing | 2025 |
| KAM Reporting Ltd | Health & social care | 2024 |
| Kamakura Ballymena NI Ltd | Hospitality | 2025 |
| Kamakura Group NI Ltd | Administrative & support | 2025 |
| Kamakura Sushi&Ramen Limited | Hospitality | 2017 |
| Kamas Properties Limited | Real estate | 2005 |
| Kami Intelligence Limited | Information & communication | 2017 |
| Kams Booking Ltd | Administrative & support | 2023 |
| Kamus Developments Limited | Real estate | 2005 |
| Kanagawa Sushi and Ramen Limited | Hospitality | 2023 |
| Kane Electrical and Renewables Ltd | Construction | 2020 |
| Kane Fuels Limited | Other services | 1995 |