| JAI Developments Ltd | Construction | 2014 |
| JAL (SW) Limited | Hospitality | 2019 |
| JAM (Fish & Chips) Limited | Wholesale & retail | 2011 |
| James Owen Strength and Conditioning Limited | Health & social care | 2021 |
| James William & Co Capital Ltd | Financial services | 2025 |
| Jason Waterman Holdings Ltd | Professional & scientific | 2025 |
| JB Marine International Ltd | Manufacturing | 2022 |
| JC Construction Cornwall Ltd | Manufacturing | 2023 |
| JD Sustainable Ltd | Professional & scientific | 2025 |
| JEC Groundworks Ltd | Construction | 2020 |
| Jencarbea Consulting Ltd | Professional & scientific | 2026 |
| Jennifer Otter Bickerdike Ltd | Professional & scientific | 2021 |
| Jesamari Ltd | Health & social care | 2025 |
| Jewell Estates Limited | Real estate | 2019 |
| Jimmy's Plumbing & Heating Limited | Construction | 2013 |
| Jinks Properties Ltd | Real estate | 2019 |
| JJ Developments Newquay Ltd | Construction | 2021 |
| JJ Electrical & Plumbing Contractors Limited | Construction | 2015 |
| JJA Events Ltd | Hospitality | 2013 |
| JMG (Southwest) Limited | Health & social care | 2013 |
| Jodie Young Colour Limited | Other services | 2024 |
| Joe's Digger Services Ltd | Construction | 2015 |
| Joefish Digital Limited | Professional & scientific | 2025 |
| Joefish Limited | Professional & scientific | 2023 |
| Join the Groundswell CIC | Arts & recreation | 2023 |
| JON Bouys Limited | Hospitality | 2024 |
| JON Jewell Electrical Limited | Construction | 2016 |
| Jpfp Ltd | Professional & scientific | 2019 |
| JRG GAS Services Ltd | Construction | 2026 |
| JTT Management Co. NO.1 Ltd | Financial services | 2018 |
| JTT Management Co. NO.2 Ltd | Financial services | 2018 |
| Jummp Group Ltd | Financial services | 2015 |
| Jungle Jack's Limited | Arts & recreation | 2013 |
| Junior Childcare Limited | Education | 2007 |
| Jushz Furnishings Limited | Manufacturing | 2017 |
| Just Good Pubs Ltd | Hospitality | 2022 |
| Just Trek Ltd | Information & communication | 2016 |
| JVW Fitness Ltd | Arts & recreation | 2025 |
| JWD Mortgages Limited | Financial services | 2019 |
| JWM Cleaning Ltd | Administrative & support | 2021 |
| K & G Oakley Ltd | Hospitality | 2010 |
| K & R Hair Ltd | Other services | 2015 |
| K Apartments Management Company Limited | Households | 2023 |
| K J Evans (Builders) Limited | Construction | 2012 |
| K&D Supermarket Ltd | Wholesale & retail | 2018 |
| K&R Building Ltd | Construction | 2011 |
| K&R Project Services Limited | Construction | 2015 |
| K-Cube Conglomerate Limited | Health & social care | 2025 |
| K. Mews (Newquay) Property Management Company Limited | Households | 2017 |
| K. Ridsdale & Sons Ltd | Construction | 2020 |
| K.Brown S/W Ltd | Construction | 2019 |
| Kalma Properties Ltd | Financial services | 2025 |
| Kara Counselling Ltd | Health & social care | 2022 |
| Karlin Limited | Wholesale & retail | 2012 |
| Karn Havos Management Company Limited | Households | 2017 |
| Kasin Design Ltd | Real estate | 2025 |
| Katie LEE Design Ltd | Arts & recreation | 2022 |
| KB Roofing (Cornwall) Ltd | Construction | 2022 |
| KC Offshore Services Ltd | Professional & scientific | 2023 |
| KD Kernow Delights Ltd | Manufacturing | 2026 |
| Keeping Cows Moovin Limited | Information & communication | 2023 |
| Kemeneth Developments Limited | Real estate | 2025 |
| Kendall Crop Spraying Limited | Agriculture & fishing | 2014 |
| Kendall Farming Ltd | Agriculture & fishing | 2023 |
| Kerbside Food Company Limited | Hospitality | 2017 |
| Kerenza Ltd | Hospitality | 2014 |
| Kernewek Roofing Limited | Construction | 2024 |
| Kernick House Management Limited | Professional & scientific | 2002 |
| Kernow Academy CIC | Education | 2024 |
| Kernow Accountants Ltd | Professional & scientific | 2021 |
| Kernow CAB Hire Ltd | Transport & logistics | 2022 |
| Kernow Commercials Ltd | Wholesale & retail | 2022 |
| Kernow Copiers Ltd | Manufacturing | 2025 |
| Kernow Drylining Limited | Construction | 2018 |
| Kernow Investment Services Limited | Financial services | 1972 |
| Kernow Learning Multi Academy Trust | Education | 2010 |
| Kernow Offshore Ltd | Professional & scientific | 2026 |
| Kernow Sport & Leisure Ltd | Arts & recreation | 2009 |
| Kernow Systems Limited | Information & communication | 2020 |
| Kernow Trading Company Limited | Wholesale & retail | 2006 |
| Kernow Training Limited | Education | 2014 |
| Kernow Tuition Limited | Education | 2024 |
| Kernow Ventures Ltd | Administrative & support | 2016 |
| Kernow Welding Ltd | Manufacturing | 2014 |
| Kernowek Projects Ltd | Manufacturing | 2025 |
| Kerry's Travel Limited | Transport & logistics | 2018 |
| Kevin and Elvis Ltd | Wholesale & retail | 2023 |
| Keyline Solutions Limited | Administrative & support | 2018 |
| KHM Solutions Ltd | Other services | 2011 |
| Kikis Desserts Ltd | Hospitality | 2025 |
| Killas and Dowr Estates Limited | Real estate | 2025 |
| KIN Carpentry and Construction Ltd | Construction | 2025 |
| Kincaid 1969 Limited | Extraterritorial | 2014 |
| Kind Transport Ltd | Transport & logistics | 2023 |
| Kindred Health Limited | Health & social care | 2015 |
| Kingsley Developments (S W) Limited | Hospitality | 2012 |
| Kingsley Holiday Parks Limited | Construction | 2020 |
| Kingsley Homes Limited | Real estate | 2017 |
| Kingsley Leisure Developments Limited | Real estate | 2017 |
| Kingsley Planning Consultancy LLP | | 2016 |