| Hudson ST Ives Limited | Wholesale & retail | 2000 |
| Hunter Walsh Limited | Other services | 2011 |
| Hyperdiary Limited | Information & communication | 2024 |
| IAM Bands Ltd. | Wholesale & retail | 2012 |
| IAN Gower Ltd | Information & communication | 2021 |
| Icarus for MEN Limited | Wholesale & retail | 2025 |
| Icknield Way Investments LLP | | 2008 |
| Icls Trading Limited | Financial services | 2013 |
| Ignite Power Solutions Limited | Information & communication | 2025 |
| Ignite SAP Resources Ltd | Administrative & support | 2020 |
| Iktin Solutions Limited | Construction | 2023 |
| Inanity Limited | Construction | 2013 |
| Incandescent Design Ltd. | Administrative & support | 1999 |
| Inchscape Holdings Limited | Hospitality | 2025 |
| Incite Services Limited | Extraterritorial | 2016 |
| Independent Creative Enterprizes Ltd | Wholesale & retail | 2014 |
| Indibox Limited | Extraterritorial | 2016 |
| Indulgence Catering Limited | Hospitality | 2013 |
| Insite Construction Management Ltd | Construction | 2025 |
| Inspirations by the Sea LLP | | 2026 |
| Inspired Conservatories Direct Ltd | Construction | 2020 |
| Intellinetz Ltd | Administrative & support | 2025 |
| International Artists Rostrum Ltd | Arts & recreation | 2025 |
| Invest in Art UK Ltd | Wholesale & retail | 2013 |
| IO PHI Trading Ltd | Wholesale & retail | 2022 |
| Island Transfers Limited | Transport & logistics | 2022 |
| Isles of Scilly Parking Company Limited | Transport & logistics | 2007 |
| Isles of Scilly Property Holdings Limited | Real estate | 2024 |
| Isles of Scilly Shipping Company Limited | Transport & logistics | 2004 |
| Isles of Scilly Skybus Limited | Transport & logistics | 1984 |
| Isles of Scilly Travel Limited | Extraterritorial | 2014 |
| Istanbul Turkish Barber PZ Ltd | Other services | 2023 |
| IT Consultants Services Ltd. | Construction | 2012 |
| IVY & ST Nicholas Limited | Real estate | 2021 |
| J & T Lord Ltd | Health & social care | 2019 |
| J B Construction (SW) Limited | Construction | 2021 |
| J F Consultancy (York) Limited | Professional & scientific | 2015 |
| J KAY Properties Limited | Real estate | 2003 |
| J R Howard Consulting Ltd | Professional & scientific | 2019 |
| J Thomas Holdings Limited | Financial services | 2022 |
| J&N Hospitality Limited | Hospitality | 2021 |
| J.E. & S.M. Pryce (Chiropodists) Limited | Health & social care | 2003 |
| J.R.C. - Art Services Ltd | Arts & recreation | 2018 |
| J.T. Fabrication & Engineering Ltd | Manufacturing | 2009 |
| J.W.Pearce Agricultural Services Limited | Manufacturing | 2013 |
| Jabex Limited | Real estate | 2020 |
| Jack Gurdon Video Services Limited | Arts & recreation | 2025 |
| Jack Shannon Developments Limited | Construction | 2017 |
| Jackinabox Cornwall Ltd | Administrative & support | 2021 |
| Jackson (Life & Pensions) Limited | Financial services | 1974 |
| Jado Corp Limited | Real estate | 2021 |
| JAL Outdoor Eats Ltd | Hospitality | 2025 |
| Jasper Electrical Ltd | Construction | 2024 |
| Jchmicro Limited | Health & social care | 2026 |
| Jess Allen Artist Ltd | Wholesale & retail | 2023 |
| Jewell Anaesthetic Medical Services Limited | Health & social care | 2015 |
| JEX Properties Limited | Extraterritorial | 2009 |
| JH Lighting Services Limited | Information & communication | 2018 |
| Jhallsolutions Limited | Administrative & support | 2014 |
| JHK Medical Services Limited | Health & social care | 2015 |
| JJ Cornwall Scaffolding Ltd | Construction | 2019 |
| JKP Creations Ltd | Other services | 2024 |
| JLP Group Cornwall Limited | Financial services | 2024 |
| JLP Holdings Cornwall Limited | Financial services | 2021 |
| JMB183 Limited | Wholesale & retail | 2023 |
| JN Studios South West Limited | Professional & scientific | 2023 |
| Jojo Transport Ltd | Transport & logistics | 2026 |
| JON Pearson Limited | Professional & scientific | 2016 |
| Jowanna Conboye Consulting Limited | Professional & scientific | 2021 |
| Jrj.Studio Ltd | Arts & recreation | 2024 |
| Jtsw Limited | Real estate | 2022 |
| Jubilee Pool Café CIC | Hospitality | 2018 |
| Just Cape Limited | Hospitality | 2021 |
| Just Makes Scents Ltd | Wholesale & retail | 2016 |
| Just Pet Care Limited | Wholesale & retail | 2014 |
| Justin Duance Limited | Manufacturing | 2015 |
| Justin Lusher Mortgages Limited | Professional & scientific | 2011 |
| Justlife.Art CIC | Arts & recreation | 2023 |
| JW Groundworks & Plant Hire Ltd | Construction | 2022 |
| K.A. Stockham (Electrical) Limited | Construction | 2002 |
| Kalantzis Maxillofacial Limited | Health & social care | 2023 |
| Kate Butcher Consultancies Ltd | Health & social care | 2013 |
| Kate Collects Ltd | Wholesale & retail | 2026 |
| Kate Newby Limited | Other services | 2017 |
| KDF Garage Services Ltd | Wholesale & retail | 2026 |
| Kebab Baba TR18 Ltd | Hospitality | 2025 |
| Keep Going Fitness Ltd | Wholesale & retail | 2025 |
| Kelynack Limited | Hospitality | 2005 |
| Kemeneth Creatives CIC | Arts & recreation | 2025 |
| Kemp Cardiology Limited | Health & social care | 2023 |
| Kenneggy Cove Caravan Park Limited | Hospitality | 2001 |
| Kenneggy Cove Holiday Park Limited | Hospitality | 2001 |
| Kenneggy Crafts Ltd | Manufacturing | 2023 |
| Kenshatori Limited | Professional & scientific | 2021 |
| Kenython Ltd | Arts & recreation | 2025 |
| Kernow Aesthetic Surgery Limited | Health & social care | 2015 |
| Kernow Anaesthetic Services LLP | | 2019 |
| Kernow Coasteering Limited | Arts & recreation | 2025 |
| Kernow Developers (Cornwall) Limited | Construction | 2014 |
| Kernow Hand Surgery Limited | Health & social care | 2015 |