| House of Jurassic Ltd | Wholesale & retail | 2025 |
| Howard FRY Carpentry Ltd | Construction | 2005 |
| HU BU Limited | Information & communication | 2007 |
| Hubbleday Limited | Information & communication | 2022 |
| Hydrezen Ltd. | Manufacturing | 2023 |
| I CAN BE Limited | Wholesale & retail | 2015 |
| I Marsh & SON Limited | Construction | 2002 |
| I T B Gardening and Tree Care Ltd | Administrative & support | 2012 |
| I.H. Property Ltd | Construction | 2011 |
| II Direct Limited | Construction | 2022 |
| Imove Purbeck MAN & Van Ltd | Wholesale & retail | 2025 |
| Improve Profit Solutions Limited | Professional & scientific | 2012 |
| Incledon Court Freehold Limited | Households | 2003 |
| Incledon Court Management Company (Swanage) Limited | Households | 1983 |
| Incledon Management Company (Swanage) Limited | Households | 1983 |
| Inner Strength Martial Arts Ltd | Education | 2019 |
| Inspire Oakdale Ltd | Other services | 2017 |
| Intrigue Hair Designs Limited | Other services | 2009 |
| IOT Services Ltd | Information & communication | 2020 |
| IOT Solutions Group Ltd | Information & communication | 2018 |
| IOT Solutions Ltd | Extraterritorial | 2023 |
| Ipconsult Limited | Professional & scientific | 2007 |
| Ipintangible Limited | Professional & scientific | 2010 |
| IS Landscaping and Tree Services Limited | Administrative & support | 2011 |
| Isle of Purbeck Golf Club Limited | Arts & recreation | 1965 |
| Italian Bakery Broadstone Ltd | Wholesale & retail | 2026 |
| IWL Services Ltd | Professional & scientific | 2015 |
| J Critchlow Taxation Services Limited | Professional & scientific | 2018 |
| J D Facilities Ltd | Other services | 2010 |
| J E Carless Consultancy Ltd | Professional & scientific | 2025 |
| J F Lander Limited | Agriculture & fishing | 2002 |
| J K V Ltd | Health & social care | 2006 |
| J M & a D Transport Ltd | Transport & logistics | 2018 |
| J M Adventure Ltd | Construction | 2002 |
| J N France Ltd | Transport & logistics | 2013 |
| J. Holland & Sons Limited | Arts & recreation | 1991 |
| J. Suttle Transport Limited | Mining & quarrying | 1993 |
| Jack Kimber Photography Ltd | Professional & scientific | 2022 |
| James Anthony Construction Ltd | Construction | 2023 |
| James Moyle Ltd | Professional & scientific | 2024 |
| Java Coffee House Ltd | Hospitality | 2020 |
| Jayka Productions Ltd | Information & communication | 2024 |
| Jazaccounts Limited | Professional & scientific | 2010 |
| Jdra Ltd | Arts & recreation | 2026 |
| Jgap Ltd | Construction | 2021 |
| JHS Leisure Limited | Financial services | 2021 |
| JJL Decorating Limited | Administrative & support | 2019 |
| JK Countryside Management Ltd | Professional & scientific | 2025 |
| JO Tasker Planning Consultant Ltd | Professional & scientific | 2022 |
| Joe's Gym Ltd | Arts & recreation | 2012 |
| John Brewster Limited | Mining & quarrying | 2003 |
| Johnjo Ltd | Construction | 2026 |
| Jonathan David Carpentry & Building Services Ltd | Construction | 2017 |
| Jonathan Living-Stone Limited | Arts & recreation | 2002 |
| Jones & Prior of Swanage Limited | Construction | 2023 |
| Josephine Wall Fine Art Ltd | Other services | 2007 |
| Josephine Wall Limited | Arts & recreation | 2002 |
| JSC Jurassic Salt Co Ltd | Mining & quarrying | 2023 |
| JSG Plumbing & Heating Limited | Construction | 2007 |
| JSR Tree Care Limited | Administrative & support | 2022 |
| JT Tree & Hedge Work Ltd. | Administrative & support | 2020 |
| JTH Media Ltd | Information & communication | 2026 |
| Juana Florist&Beauty Limited | Wholesale & retail | 2026 |
| Juicy One (Wareham) Ltd | Wholesale & retail | 2018 |
| Jumpin Star Limited | Arts & recreation | 2000 |
| JUNIPER2 Advisory Limited | Professional & scientific | 2011 |
| Jupiter Roofing Ltd | Construction | 2024 |
| Jurassic Bars Ltd | Hospitality | 2026 |
| Jurassic Marine Ltd | Wholesale & retail | 2017 |
| Jurassic Outdoor Limited | Wholesale & retail | 2009 |
| Jurassic Spring Water Ltd | Manufacturing | 2013 |
| Just One Body Limited | Health & social care | 2017 |
| Jwcoding Ltd | Information & communication | 2025 |
| Keates Quarries Limited | Mining & quarrying | 2012 |
| KER Associates Limited | Professional & scientific | 1999 |
| Kevin Wells Electrical Limited | Construction | 2002 |
| Keysworth Engineering Services Ltd. | Manufacturing | 2000 |
| Kickstart Works Limited | Construction | 2000 |
| Kidzbuks Ltd | Information & communication | 2012 |
| Kimber Biomedical Limited | Professional & scientific | 2009 |
| Kinburn Street Consulting Ltd | Information & communication | 2016 |
| Kings Arms (Langton) Ltd | Hospitality | 2009 |
| Kings Kabs Ltd | Transport & logistics | 2009 |
| Kingsbere Court Management Company Limited | Households | 1994 |
| Kingsley Hall Residents Company Limited | Households | 1992 |
| Kingsley Road Properties Limited. | Extraterritorial | 1989 |
| Kingston Water Ltd | Water & waste | 2024 |
| Kingswood Investment and Holdings Limited | Financial services | 2025 |
| Kitchener Cottage Ltd | Manufacturing | 2016 |
| KJK Service Ltd | Professional & scientific | 2023 |
| KM Supermarkets Limited | Wholesale & retail | 2002 |
| Kneecraft Design Ltd | Manufacturing | 2015 |
| Knollsea Management Ltd | Hospitality | 2006 |
| Koch (Swanage) Limited | Other services | 2018 |
| Kombi Klassics Limited | Wholesale & retail | 2005 |
| Komodo Holdings Ltd | Hospitality | 2026 |
| KPM Property Management Ltd | Households | 2023 |
| Kuehnle Agrosystems UK Limited | Manufacturing | 2026 |
| L Parker Building Services Ltd | Construction | 2026 |
| Lammerva Limited | Real estate | 2014 |