| Iremidic Media Ltd | Professional & scientific | 2025 |
| Isle of Wight School Journeys Limited | Extraterritorial | 1992 |
| Itazura Ltd | Information & communication | 2015 |
| ITS Designs Limited | Manufacturing | 2003 |
| ITW Consulting Services Ltd | Administrative & support | 2022 |
| J Abell Brickwork Limited | Construction | 2025 |
| J Clarke Farm Services Ltd | Extraterritorial | 2024 |
| J Clarke Services Ltd | Transport & logistics | 2021 |
| J F Brown UAV Limited | Professional & scientific | 2019 |
| J.B. Tool Hire Limited | Administrative & support | 1987 |
| J.Clifton & Company Limited | Agriculture & fishing | 1951 |
| J.G.Parker Limited | Extraterritorial | 1960 |
| J.R.K. Property Development Limited | Real estate | 2020 |
| J1 Transport Limited | Transport & logistics | 2024 |
| Jacana Investments Limited | Real estate | 2004 |
| Jack Browns Bistro Limited | Hospitality | 2019 |
| Jacklings Properties Ltd | Real estate | 2024 |
| Jackstar Events Ltd | Arts & recreation | 2016 |
| Jadez Events Ltd | Administrative & support | 2025 |
| JAH Property Investments Ltd | Real estate | 2020 |
| James Baxter Haulage Limited | Transport & logistics | 2003 |
| James MAY and Company Limited | Wholesale & retail | 2012 |
| Janellis (NO. 2) Limited | Professional & scientific | 1958 |
| Janton Limited | Manufacturing | 1990 |
| Jartrivtech Ltd | Information & communication | 2026 |
| JAS Fish and Chips Ltd | Hospitality | 2024 |
| JAY Mahadev Retail Ltd | Wholesale & retail | 2025 |
| JB Health Limited | Manufacturing | 2020 |
| Jbca Investments Ltd | Real estate | 2026 |
| JBE Distributions Ltd | Wholesale & retail | 2026 |
| Jcjs Estates Ltd | Real estate | 2016 |
| JD Developing Ltd | Real estate | 2017 |
| JDB Automotive Services Ltd | Wholesale & retail | 2025 |
| JDP Consultancy Services Ltd | Professional & scientific | 2025 |
| JEA Ltd | Financial services | 2020 |
| Jenik Properties Limited | Real estate | 2019 |
| JF & JF Properties Limited | Real estate | 2019 |
| JF Fire & Security Ltd | Administrative & support | 2025 |
| Jfk-Bs Property Ltd | Real estate | 2018 |
| Jgautospace Ltd | Wholesale & retail | 2024 |
| JHR Electrical Services Ltd | Construction | 2016 |
| JHS Breakdown Recovery & Mobile Tyres Ltd | Wholesale & retail | 2023 |
| JJC Electrical & Maintenance Ltd | Construction | 2023 |
| JK Red Ltd | Wholesale & retail | 2026 |
| JMK Motors Limited | Wholesale & retail | 2023 |
| JMW Childcare Ltd | Health & social care | 2025 |
| JOE Care Ltd | Health & social care | 2026 |
| Joetany by Design Ltd | Health & social care | 2013 |
| John Merison (Building Maintenance Contractors) Limited | Construction | 1997 |
| John S Gordon Ltd | Professional & scientific | 2020 |
| Johns Iphone and Ipad Repairs Ltd | Manufacturing | 2022 |
| JOLLYPOTTERS2012 Ltd | Hospitality | 2011 |
| Joseph IVY Limited | Real estate | 2025 |
| Joy in Health CIC | Public administration | 2021 |
| Joychinwe Ltd | Information & communication | 2018 |
| JSB Properties Ltd | Real estate | 2004 |
| JSB Tree Surgery Ltd | Agriculture & fishing | 2021 |
| JSW Rail Ltd | Construction | 2023 |
| JTS Biker Clothing Limited | Manufacturing | 2005 |
| Jubilee House Holdings 1 Limited | Other services | 2024 |
| Jubilee House Holdings 2 Limited | Other services | 2024 |
| Judge Estate Agents Ltd | Real estate | 2010 |
| Juergen Koch Limited | Wholesale & retail | 2003 |
| Juliet Brooke Podiatry & Chiropody Services Ltd | Other services | 2015 |
| Juno Building Company Ltd | Construction | 2024 |
| Jupiter Commercial Ltd | Wholesale & retail | 2022 |
| Just in Time Accountants Limited | Professional & scientific | 2024 |
| Just Ride Limited | Information & communication | 2019 |
| JWL Falconry Ltd | Wholesale & retail | 2015 |
| K D Retail Limited | Wholesale & retail | 2009 |
| K Mcintyre Consulting Limited | Professional & scientific | 2021 |
| K N Construction & Building Ltd | Construction | 2025 |
| K Stafford Renewables and Construction Ltd | Construction | 2025 |
| K-Flex (UK) Ltd | Wholesale & retail | 2006 |
| K.C.R. Service & MOT Centre Limited | Wholesale & retail | 2017 |
| K.R.M.Concrete Limited | Professional & scientific | 1994 |
| KAD Mortgages Limited | Financial services | 2021 |
| Kambek Ltd | Manufacturing | 2016 |
| Kaos INK Ltd | Other services | 2010 |
| Karing Hands Ltd | Health & social care | 2020 |
| Kasa Property Holdings Limited | Real estate | 2020 |
| Kaskoz Ltd | Transport & logistics | 2018 |
| KAW Midlands Ltd | Other services | 2017 |
| Kaye Property Management Ltd | Real estate | 2023 |
| KB Ascent Ltd | Professional & scientific | 2025 |
| KBG Engineering Limited | Manufacturing | 2021 |
| Kealoha 11 Limited | Construction | 2000 |
| Kealoha Limited | Professional & scientific | 2000 |
| Kediis-Kia Ltd | Health & social care | 2017 |
| Keeday Leisure Limited | Financial services | 2015 |
| Kendall Bros. (Portsmouth) Limited | Professional & scientific | 1950 |
| Kendricks Engineering Limited | Administrative & support | 2013 |
| Kendricks Property Management Group Limited | Real estate | 2021 |
| Kenray Forming Limited | Manufacturing | 2004 |
| Kenray Holding Limited | Financial services | 2020 |
| Kenway Construction Limited | Construction | 2004 |
| KERN25 Limited | Transport & logistics | 2014 |
| KES M Limited | Wholesale & retail | 2021 |
| Kev's Van Rentals T/A Van Hire Coalville Ltd | Transport & logistics | 2015 |
| Key 4 ADS Limited | Wholesale & retail | 2017 |