| Intelligent Plant Safety Ltd | Administrative & support | 2025 |
| Interior Tailors Limited | Other services | 2021 |
| Investment and Tax Advisory Services Limited | Financial services | 2001 |
| Invogue Events and Entertainment Ltd | Arts & recreation | 2025 |
| Inwood Design Limited | Construction | 2013 |
| Iona & Lime Ltd | Wholesale & retail | 2025 |
| Ionian Property Services UK Limited | Hospitality | 2016 |
| Ionosphere Engineering Ltd | Information & communication | 2015 |
| IOS Fifteen Limited | Financial services | 2026 |
| IPP Global Print Limited | Manufacturing | 2003 |
| Irbs Business Services Limited | Professional & scientific | 2017 |
| Ireosa Limited | Agriculture & fishing | 1981 |
| Iron Works Dorset Ltd | Manufacturing | 2020 |
| ISA Care Services Limited | Administrative & support | 2022 |
| Isha Body Jewellery Ltd | Wholesale & retail | 2023 |
| Island Home Improvements Limited | Construction | 2010 |
| Island Training Partnership Limited | Real estate | 2006 |
| Isles Finance Limited | Financial services | 2026 |
| Isomark Ltd | Wholesale & retail | 1999 |
| Istanbul DT1 Limited | Hospitality | 2025 |
| Ithaca NR 26 Limited | Construction | 2022 |
| ITHACA7 Engineers & Designers Ltd | Information & communication | 2015 |
| Izli Limited | Construction | 2025 |
| J & H Property Services Ltd. | Construction | 2016 |
| J & K Dorset Hospitality Ltd | Hospitality | 2025 |
| J Baggley Building Ltd | Construction | 2003 |
| J H R Consultants Limited | Education | 2015 |
| J Hardy Civils Limited | Construction | 2020 |
| J J Marshall Associates Limited | Professional & scientific | 2002 |
| J Mato & SON Limited | Wholesale & retail | 1997 |
| J P Free Ltd | Construction | 2018 |
| J R S Supplies Ltd | Wholesale & retail | 2023 |
| J R Wickham Ltd | Construction | 2023 |
| J Sheehan Electrical Services Limited | Professional & scientific | 2015 |
| J Sugg Limited | Real estate | 2017 |
| J W Electrical Services Limited | Construction | 2003 |
| J&D Lewis Ltd | Administrative & support | 2020 |
| J.D Drivers Ltd | Transport & logistics | 2026 |
| J.H.Hall and Son(Farms)Limited | Agriculture & fishing | 1956 |
| J.Marks & Sons Roofing Ltd | Construction | 2015 |
| JAB Fit UK Limited | Arts & recreation | 2009 |
| Jacgilden Properties Limited | Real estate | 1959 |
| Jack Eames Photography Limited | Professional & scientific | 2012 |
| Jackles Jewels Limited | Manufacturing | 2023 |
| Jackson Lowry Consulting Ltd | Professional & scientific | 2013 |
| Jacqui Connor Consultancy Limited | Other services | 2020 |
| Jakub J & S Limited | Hospitality | 2024 |
| JAM Interiors Limited | Construction | 2018 |
| James & Sons Medical Services Limited | Health & social care | 2020 |
| James Aldred Limited | Administrative & support | 2011 |
| James Beresford Construction Ltd | Construction | 2021 |
| James Beresford Developments Ltd | Construction | 2023 |
| James Buglass Plumbing & Heating Limited | Construction | 2003 |
| James House Poundbury Limited | Real estate | 2015 |
| James Newsam Construction Limited | Construction | 2021 |
| James Southby Productions Limited | Administrative & support | 2012 |
| James Wood Flooring Limited | Construction | 2024 |
| Jamie Miller Recruitment Limited | Administrative & support | 2014 |
| Jamies Bars Limited | Hospitality | 2017 |
| Jamitin Limited | Information & communication | 2009 |
| Janefield Places Ltd | Hospitality | 2018 |
| Janus Global Limited | Financial services | 2023 |
| Janus PPM Limited | Wholesale & retail | 2023 |
| Jaylee Refrigeration Ltd. | Energy | 2003 |
| JB Roofing and Cleaning Ltd | Construction | 2023 |
| JBA Wessex Limited | Wholesale & retail | 2015 |
| JBT Equine Transport Limited | Transport & logistics | 2019 |
| JCC Dorset Ltd | Hospitality | 2007 |
| JCW 3D Systems Ltd | Professional & scientific | 2007 |
| JD Yachts Limited | Wholesale & retail | 2003 |
| JD43 Limited | Hospitality | 2026 |
| JDC Cleaning Solutions Limited | Administrative & support | 2023 |
| JDT Assets LLP | | 2017 |
| JDT Power Limited | Construction | 2009 |
| JDT Utilities Limited | Construction | 2010 |
| Jdtu Holdings Limited | Financial services | 2014 |
| Jdtu Investments LLP | | 2014 |
| Jebah Ltd | Administrative & support | 2008 |
| Jenns UK Ltd | Hospitality | 2020 |
| Jenny Barnes & Co Limited | Professional & scientific | 2003 |
| Jenny Greenhow Jewellery Ltd | Manufacturing | 2016 |
| Jennysis Ltd | Wholesale & retail | 2002 |
| Jeremy Bowden Ltd | Information & communication | 2013 |
| JET Dorset Limited | Transport & logistics | 2018 |
| JEZ MC Catering Ltd | Hospitality | 2021 |
| JF Carpentry (Dorset) Ltd | Construction | 2024 |
| Jfelc Properties Limited | Real estate | 2022 |
| JG Crocker Holdings Ltd | Financial services | 2025 |
| JGS Capital Limited | Financial services | 2023 |
| JH Play Limited | Hospitality | 2025 |
| Jkanaesthesia LLP | | 2026 |
| JKJ Services Limited | Administrative & support | 2005 |
| Jkma Ltd | Professional & scientific | 2020 |
| JM Cloud Technologies Ltd | Information & communication | 2024 |
| JMS Wealth Management Ltd | Financial services | 2021 |
| Jmsgld Limited | Professional & scientific | 2011 |
| JO Forsey Equestrian Ltd | Arts & recreation | 2025 |
| Joey's Doggie Day Care Limited | Other services | 2017 |
| John Broddle Monumental Mason Limited | Administrative & support | 2000 |
| John Coleman & Sons(Farmers)Limited | Agriculture & fishing | 1961 |