| Hydrogen Boat Centre, Cornwall Limited | Transport & logistics | 2023 |
| I.A.B. Bodyworks Limited | Wholesale & retail | 2003 |
| I2ISO Limited | Professional & scientific | 2014 |
| IAN Dawkins LLP | | 2026 |
| Ibbynet Ltd | Professional & scientific | 2024 |
| Ilow Events Group Limited | Financial services | 2020 |
| Ilow HQ Limited | Arts & recreation | 2018 |
| Immoinrent Beratungs- UND Vermittlungsgesellschaft Ltd | Administrative & support | 2019 |
| Influx Group Solutions Limited | Information & communication | 2020 |
| Inspicere Ltd | Construction | 2014 |
| International Port Services Limited | Transport & logistics | 2019 |
| Intertide C.I.C. | Wholesale & retail | 2022 |
| Into the Wild Cornwall Ltd | Administrative & support | 2017 |
| Intrastore Self Storage Ltd | Transport & logistics | 2023 |
| Invita Intelligence Care Solutions Limited | Information & communication | 1997 |
| Invita Intelligence Limited | Information & communication | 2023 |
| Iron Coast Security Ltd | Administrative & support | 2025 |
| Isaac Barco Mortgages Ltd | Financial services | 2025 |
| Isystems Tech Ltd | Administrative & support | 2017 |
| Ital Holdings (Cornwall) Ltd | Real estate | 2025 |
| Ivey Veterinary Acupuncture Ltd | Professional & scientific | 2016 |
| Ivygreen Lets Ltd | Real estate | 2024 |
| J & a Allely Limited | Construction | 1996 |
| J Pascoe Electrical Ltd | Other services | 2020 |
| J S Trice Associates Ltd | Financial services | 2021 |
| J&E Management Ltd | Hospitality | 2025 |
| J.C. & F.C. Tripconey Limited | Agriculture & fishing | 2014 |
| J.C. Williams and Sons (Helston) Limited | Real estate | 1959 |
| J.C.Williams & Sons(Investments)Limited | Hospitality | 1960 |
| Jacha (UK) Limited | Professional & scientific | 2014 |
| Jack Johns Ltd | Professional & scientific | 2015 |
| JAM First Store Ltd | Wholesale & retail | 2021 |
| James Helliwell Consulting Ltd | Professional & scientific | 2025 |
| James Johnstone Limited | Professional & scientific | 2005 |
| JAR Hill Limited | Wholesale & retail | 2010 |
| JB & Sons Developments Ltd | Construction | 2017 |
| JCH Plastering & Renovations Limited | Construction | 2009 |
| Jencucco Ltd | Agriculture & fishing | 2024 |
| Jevin Homes Ltd | Real estate | 2019 |
| JFW Pressure Washing Ltd | Administrative & support | 2024 |
| JG Highway Design Ltd | Construction | 2020 |
| Jhpdev Ltd | Information & communication | 2025 |
| JJ Fine Homes Developers Ltd | Construction | 2020 |
| JJ Fine Homes Ltd | Hospitality | 2016 |
| JJ Lets Cornwall Ltd | Real estate | 2025 |
| JJB Marine Services Ltd | Professional & scientific | 2023 |
| JLB Controls Limited | Construction | 2024 |
| JMH Stonemasons Ltd | Construction | 2022 |
| John Mitchell Transport Limited | Transport & logistics | 2000 |
| Join Brands Limited | Wholesale & retail | 2016 |
| Join Penzance Ltd | Wholesale & retail | 2025 |
| Jonajones Limited | Real estate | 2012 |
| Jones Drainage & Groundworks Ltd | Construction | 2018 |
| Josephine Bond Ltd | Information & communication | 2025 |
| JP Sports Management Services Limited | Arts & recreation | 2014 |
| JPM Refrigeration Ltd | Manufacturing | 2016 |
| JPS Workspace Solutions Ltd | Administrative & support | 2021 |
| JR Mcloughlin Limited | Professional & scientific | 2017 |
| Jraq Ltd | Real estate | 2025 |
| JRS Limited | Professional & scientific | 2007 |
| Jsobapt Limited | Households | 2026 |
| Just Lily Jewellery Ltd | Wholesale & retail | 2021 |
| Just Lily Property Limited | Real estate | 2023 |
| JWB Contractors Limited | Construction | 2015 |
| K & P Falmouth Limited | Hospitality | 2017 |
| K & P Truro Limited | Hospitality | 2025 |
| K&Abw Ltd | Real estate | 2025 |
| K&Abwproperties Ltd | Real estate | 2025 |
| Kamasow LLP | | 2023 |
| Kammbronn Homes Limited | Real estate | 2016 |
| Kammbronn Management Limited | Real estate | 2016 |
| Kara Dons CIC | Health & social care | 2023 |
| Kernow Accountancy Ltd | Professional & scientific | 2019 |
| Kernow Appliances Limited | Other services | 2025 |
| Kernow Asset Management Limited | Professional & scientific | 2019 |
| Kernow Bovine Services Limited | Agriculture & fishing | 2025 |
| Kernow Cabs Limited | Extraterritorial | 2014 |
| Kernow Epoxy Ltd | Wholesale & retail | 2025 |
| Kernow Fish Ltd | Wholesale & retail | 2022 |
| Kernow House Ltd | Real estate | 2025 |
| Kernow HR Consultancy Limited | Administrative & support | 2022 |
| Kernow Hub Ltd | Administrative & support | 2025 |
| Kernow Pain Clinic Limited | Health & social care | 2011 |
| Kernow Paws Ltd | Professional & scientific | 2011 |
| Kernow Payroll Ltd | Administrative & support | 2019 |
| Kernow RUM Company Limited | Wholesale & retail | 2017 |
| Kernow Smallholdings Ltd | Agriculture & fishing | 2024 |
| Kernow Structural Systems Ltd | Construction | 2014 |
| Kernoweth Homes Limited | Construction | 2006 |
| Kernowsashimi Limited | Manufacturing | 2014 |
| Kerra's Catering Limited | Hospitality | 2013 |
| Kerrier Deanery CIC | Professional & scientific | 2023 |
| Kevern Plant Hire Ltd | Construction | 2018 |
| Keynvor Construction Limited | Construction | 2025 |
| Keynvor Kitchens Limited | Manufacturing | 2024 |
| Keystone Agri Ltd | Agriculture & fishing | 2022 |
| KF Online Ltd | Manufacturing | 2014 |
| Killiow Estates Limited | Real estate | 2011 |
| Kingdom Print CIC | Other services | 2015 |
| Kiote Ltd | Professional & scientific | 2018 |