| Joscol Investments Limited | Financial services | 2022 |
| Jose & Blackler Limited | Construction | 2009 |
| Jose Consulting (Cornwall) Limited | Professional & scientific | 2015 |
| Jozefs Dream Community Interest Company | Education | 2024 |
| JPK Services Ltd | Administrative & support | 2017 |
| Jpsupplies Ltd | Extraterritorial | 2022 |
| JRE Agency UK Ltd | Health & social care | 2021 |
| Jrmm Properties Limited | Construction | 2024 |
| JS (Cornwall) Ltd | Real estate | 2023 |
| Jsanth & Sons Ltd | Wholesale & retail | 2024 |
| Juju Property Developments Ltd | Real estate | 2024 |
| Jump 4 South West Limited | Arts & recreation | 2016 |
| Junya Wellbeing CIC | Health & social care | 2024 |
| Just Perfection Hair Ltd | Other services | 2015 |
| Jwf's Services Ltd | Wholesale & retail | 2024 |
| JWR Carpentry Ltd | Construction | 2014 |
| K & D Gilbert Ltd | Construction | 2001 |
| K & K Developments Limited | Construction | 2014 |
| K and M Hearing Solutions Ltd | Wholesale & retail | 2023 |
| K Dunmore Refrigeration Limited | Wholesale & retail | 2006 |
| K J Rule & SON Limited | Wholesale & retail | 2006 |
| K Small and SON Limited | Wholesale & retail | 2015 |
| K. J. Couch Electrics Limited | | 1977 |
| K.D.M 4 Security Limited | Administrative & support | 2020 |
| K.H.J. Trethewey & Sons Limited | Financial services | 1976 |
| Kaimakami Enterprises Ltd | Construction | 2024 |
| Kaimea Ltd | Wholesale & retail | 2022 |
| Kanengo Holdco 1 Limited | Financial services | 2018 |
| Kanengo Holdco 2 Limited | Financial services | 2018 |
| Karabeck Limited | | 1985 |
| Karen Coombs HR Limited | Professional & scientific | 2016 |
| Karga Electrical Services Ltd | Construction | 2022 |
| Karibu Coaching Limited | Administrative & support | 2022 |
| Karl Purcell Carpentry Limited | Construction | 2015 |
| Karn Geoservices Ltd | Construction | 2021 |
| Karn Havos Building Company Limited | Construction | 2017 |
| Karn Havos Holdings Limited | Financial services | 2017 |
| Kartha Ltd | Administrative & support | 2016 |
| Kartha Recycling Ltd | Manufacturing | 2018 |
| Kast Architects Limited | Professional & scientific | 2014 |
| Kazzhair UK Ltd | Wholesale & retail | 2017 |
| KB and LM Business Limited | Real estate | 2020 |
| KBG Chambers Limited | Professional & scientific | 2006 |
| KC Scaffolding Solutions Ltd | Construction | 2025 |
| KCD Property Ltd | Construction | 2018 |
| KCS FAL1 Limited | Real estate | 2024 |
| KCS GOO Limited | Construction | 2026 |
| KEA Contractors Limited | Agriculture & fishing | 2006 |
| KEA Downs Properties Limited | Real estate | 2016 |
| KEA Haulage and Plant Limited | Agriculture & fishing | 2019 |
| KEA Mineral Services Ltd | Mining & quarrying | 2015 |
| KEA PRE School Limited | Education | 2008 |
| KEA Projects Ltd | Professional & scientific | 2015 |
| Keane Properties and Development Limited | Construction | 2022 |
| Kearton Whitworth Limited | Financial services | 2024 |
| Keawit Limited | Construction | 2021 |
| Kebab Truro Ltd | Hospitality | 2025 |
| Keelex 176 Limited | Health & social care | 1993 |
| Keen Leisure Holdings Limited | Financial services | 2021 |
| Kegin Koffiji Ltd | Hospitality | 2023 |
| Keith Woolcock Plumbing and Heating Ltd | Construction | 2019 |
| Keltx Fitness Racing Ltd | Arts & recreation | 2025 |
| Kemp Construction Ltd | Construction | 2021 |
| Kendall Farms Limited | Agriculture & fishing | 2011 |
| Kennall Consulting Ltd | Professional & scientific | 2018 |
| Kenneggy Investments Limited | Real estate | 2026 |
| Kensa Contracting Limited | Construction | 2012 |
| Kensa Engineering Limited | Construction | 2014 |
| Kensa Group Limited | Professional & scientific | 2005 |
| Kensa Heat Pumps Limited | Manufacturing | 1999 |
| Kensa Limited | Manufacturing | 2008 |
| Kensa Utilities Limited | Administrative & support | 2016 |
| Kenwyn Construction Limited | Wholesale & retail | 1984 |
| Kenwyn Electricals Limited | Construction | 2003 |
| Kenwyn Gardens Management Company Limited | Households | 2017 |
| Kenwyn Investments Ltd. | Real estate | 2019 |
| Kenwyn Street Management Company Limited | Households | 1993 |
| Kerensa Care Limited | Health & social care | 2020 |
| Kerensa Living | Construction | 2025 |
| Kerensa Property Limited | Real estate | 2024 |
| Kerensa Support Limited | Health & social care | 2020 |
| Kerenza Trading Ltd | Administrative & support | 2020 |
| Kerneco Property Ltd | Construction | 2024 |
| Kernoda Ltd | Wholesale & retail | 2015 |
| Kernow Baseball CIC | Arts & recreation | 2023 |
| Kernow Business Services Ltd | Other services | 2023 |
| Kernow Care Services Limited | Health & social care | 2009 |
| Kernow Conservation CIC | Professional & scientific | 2022 |
| Kernow Consult Ltd | Administrative & support | 2017 |
| Kernow DC Ltd | Construction | 2026 |
| Kernow Elite Estates Ltd | Real estate | 2017 |
| Kernow Football Alliance Ltd | Arts & recreation | 2018 |
| Kernow Forensic Services Ltd | Health & social care | 2014 |
| Kernow Fuels Ltd | Wholesale & retail | 2021 |
| Kernow Health CIC | Health & social care | 2011 |
| Kernow Health Solutions Limited | Information & communication | 2014 |
| Kernow Holdings Limited | Financial services | 2019 |
| Kernow Horizons CIC | Education | 2025 |
| Kernow Kayaks Ltd | Manufacturing | 2012 |
| Kernow Lighthouse CIC | Education | 2024 |