| JS Doors Limited | Manufacturing | 2023 |
| JS Technologies Ltd | Information & communication | 2024 |
| JSA Landscaping Ltd | Administrative & support | 2022 |
| JSR Solutions Ltd | Energy | 2021 |
| JSV Trade Services Ltd | Manufacturing | 2014 |
| JSV Transport Ltd | Transport & logistics | 2018 |
| JT Financial Management Limited | Financial services | 2014 |
| Jtfm Holdings Limited | Extraterritorial | 2024 |
| JTS Business Services Limited | Professional & scientific | 2016 |
| Jubilee Aviation Support Services Ltd | Transport & logistics | 2020 |
| Juliet Tripp Limited | Other services | 2021 |
| Junk IBU Limited | Other services | 2015 |
| Just AG Ltd | Professional & scientific | 2019 |
| Just Nails (UK) Limited | Other services | 2005 |
| Just Style Ltd | Hospitality | 2024 |
| K & R Finishes Limited | Construction | 2024 |
| K &K Kabobara Ltd | Real estate | 2026 |
| K Bassett Consulting Ltd | Professional & scientific | 2023 |
| K.A.Burling Consultancy Ltd | Professional & scientific | 2023 |
| K2A Projects Ltd | Construction | 2025 |
| K9 Capital Ltd | Professional & scientific | 2018 |
| Kainth Investments Ltd | Real estate | 2021 |
| Kainth Properties Ltd | Real estate | 2019 |
| KAL & KAL Ltd | Real estate | 2025 |
| KAL Aviation Services Limited | Administrative & support | 2011 |
| Kalakoda Media Group Limited | Information & communication | 2025 |
| Kalash Limited | Hospitality | 2014 |
| Kaleidoscope Motorcycles Limited | Wholesale & retail | 2018 |
| Kaleidoscope Rooms Limited | Hospitality | 2024 |
| Kallisto Consultancy Limited | Professional & scientific | 2012 |
| Kamovski Ltd | Transport & logistics | 2015 |
| Kanadevia Inova UK Holding Limited | Financial services | 2024 |
| Kanadevia Inova UK Limited | Manufacturing | 2012 |
| Kanadevia Inova UK Operations Limited | Manufacturing | 2021 |
| Kanishka Food & Wine Limited | Wholesale & retail | 2019 |
| KAP Project Solutions Ltd | Construction | 2016 |
| Karia Ventures Ltd | Information & communication | 2023 |
| Karki Education Alliance Ltd | Education | 2024 |
| Karma Property Management Ltd | Real estate | 2025 |
| Katangha Limited | Construction | 2012 |
| Katie's Pet Heaven Ltd | Other services | 2021 |
| Katie’S Pet Haven 2025 Ltd | Other services | 2025 |
| Kaycee Consulting Ltd | Information & communication | 2025 |
| Kaydren Limited | Hospitality | 2021 |
| Kaydren Properties Limited | Real estate | 2023 |
| Kazakh Projects Joint Venture Limited | Administrative & support | 2008 |
| KB Bricks Limited | Real estate | 2025 |
| KBS Data Limited | Information & communication | 2013 |
| KCL Maintenance Ltd | Water & waste | 2026 |
| KCS Cleaning Solutions Limited | Administrative & support | 2013 |
| Keasons Ltd | Real estate | 2023 |
| Keell Construction Ltd | Construction | 2019 |
| Keep Thinking Big Limited | Professional & scientific | 2013 |
| Keepmovingphysio Ltd | Health & social care | 2025 |
| Kellows Carpentry Ltd | Manufacturing | 2022 |
| Kensington Rebirth Limited | Hospitality | 2018 |
| Kerber Charlesworth Limited | Transport & logistics | 2014 |
| Kerbian Ltd | Information & communication | 2009 |
| Kernsaw Builders Limited | Construction | 2007 |
| Kernsaws Property Ltd | Real estate | 2025 |
| Kerr & Watson Limited | Financial services | 2020 |
| KEW Road (1981) Limited | Construction | 2015 |
| Keypillar Property Ltd | Households | 2025 |
| Keystone Groundworks Ltd | Construction | 2024 |
| Kgnr.Industry Limited | Professional & scientific | 2025 |
| KGW Group Limited | Professional & scientific | 2015 |
| Khali Ltd | Wholesale & retail | 2024 |
| Khambhu Construction Ltd | Construction | 2023 |
| Khambhu Security Ltd | Financial services | 2023 |
| Khimdung Homes Ltd | Real estate | 2025 |
| Kinapse Limited | Professional & scientific | 2005 |
| Kinetic Touring Ltd | Extraterritorial | 2019 |
| Kingdom of Castles Ltd | Administrative & support | 2018 |
| Kings Court (Farnborough) Limited | Real estate | 2002 |
| Kingsbridge Estate Agents Ltd | Real estate | 2019 |
| Kingsbury Local Limited | Wholesale & retail | 2025 |
| Kingsley Developments Limited | Construction | 1993 |
| Kingswood Lettings Ltd | Real estate | 2001 |
| Kingswood Property Developments (South) Ltd | Construction | 2015 |
| Kinswood Eggs Limited | Agriculture & fishing | 1971 |
| Kirk Dalgairns Ltd | Information & communication | 2021 |
| Kizlon Ltd | Manufacturing | 2016 |
| KJG Holdings Ltd | Real estate | 2023 |
| KJH Consulting Ltd | Administrative & support | 2008 |
| KKV68 Ltd | Hospitality | 2025 |
| Klassit.Com Ltd | Information & communication | 2021 |
| KM SYI Business Ltd | Other services | 2026 |
| KMC Entertainment Limited | Hospitality | 2026 |
| Knight Land Management Ltd | Agriculture & fishing | 2010 |
| Know the Web Limited | Information & communication | 2012 |
| Knowle Farm Enterprises Ltd | Construction | 2018 |
| Knownow Limited | Information & communication | 2016 |
| Kobba Company Limited | Construction | 2025 |
| Komaitai Ltd | Manufacturing | 2016 |
| Kona Development Ltd | Construction | 2012 |
| Kona Partnership Ltd | Professional & scientific | 2017 |
| Korizo Ltd | Wholesale & retail | 2025 |
| Korora Solutions Limited | Wholesale & retail | 2018 |
| Kosara Holding Limited | Financial services | 2025 |
| Kosiba Carpentry Ltd | Construction | 2016 |