| IVC Technologies Ltd | Information & communication | 1993 |
| Ivel Aquatics Ltd | Construction | 2011 |
| Ivelhurst Nursing Home Limited | Health & social care | 2005 |
| J & C Symonds Ltd | Construction | 2002 |
| J & J Garrett Ltd | Real estate | 2023 |
| J & M Electrical & Mechanical Engineers Ltd | Manufacturing | 2011 |
| J & S Farming Limited | Agriculture & fishing | 2016 |
| J and J Farming Ltd | Agriculture & fishing | 2016 |
| J David Levett & Sons Limited | Agriculture & fishing | 2006 |
| J E & N M Vickery Limited | Agriculture & fishing | 2006 |
| J E C Lawrence West Hall Farm Limited | Agriculture & fishing | 2019 |
| J H Cresswell & Sons Limited | Construction | 2007 |
| J R Baker Engineering Limited | Manufacturing | 2006 |
| J S Palmer Holdings Ltd | Financial services | 2021 |
| J Sprake & Partners Limited | Agriculture & fishing | 2009 |
| J W Tabor Limited | Agriculture & fishing | 2012 |
| J&S Superstore Ltd | Wholesale & retail | 2024 |
| J.A. & E. Montgomery Limited | Agriculture & fishing | 1968 |
| J.M.Polmar Ltd | Transport & logistics | 2014 |
| J.M.Rock Services Ltd | Wholesale & retail | 2017 |
| J.T. Castle Limited | Construction | 2003 |
| J2 Tiling Ltd | Construction | 2014 |
| Jaam Design Limited | Professional & scientific | 2013 |
| Jacdee Ltd | Health & social care | 2013 |
| Jacks House Limited | Construction | 2015 |
| JAD Media Ltd | Information & communication | 2024 |
| Jagg Enterprise UK Ltd | Wholesale & retail | 2024 |
| Jaliver Rose Ltd | Information & communication | 2022 |
| Jaliver Rose Properties Ltd | Real estate | 2025 |
| Jalucha Ltd | Manufacturing | 2020 |
| James Bamford Ltd | Arts & recreation | 2025 |
| James Gillam Limited | Other services | 2002 |
| James Gisborne Limited | Construction | 2004 |
| James Verner Conservation Limited | Construction | 2021 |
| Jamie Davies Motor Sport Limited | Extraterritorial | 2007 |
| Janus Golf Ltd | Manufacturing | 2023 |
| Japan SKI Experience Limited | Administrative & support | 2012 |
| Jarmans Accountancy Ltd | Professional & scientific | 2018 |
| Jarmany Hill Developments Ltd | Construction | 2019 |
| Jason Bowen Limited | Manufacturing | 2005 |
| Jaxons Property Ltd | Real estate | 2021 |
| Jayport Limited | Professional & scientific | 1988 |
| Jays Services (South West) Limited | Administrative & support | 2009 |
| JB Tennis Court Maintenance Limited | Construction | 2022 |
| JBA Surveyors Limited | Professional & scientific | 2022 |
| JBV Holdings Limited | Real estate | 2019 |
| JBV Investments Limited | Real estate | 2019 |
| JC Fabrications (Chard) Limited | Manufacturing | 2003 |
| JD & YM Pineo and Partners Ltd | Agriculture & fishing | 2021 |
| JDK Group Ltd | Financial services | 2026 |
| Jearnie Ltd | Administrative & support | 2017 |
| Jeavons & Butler Limited | Hospitality | 2023 |
| Jenoo Ltd | Information & communication | 2016 |
| Jere Private Limited | Wholesale & retail | 2025 |
| Jeremiah C Limited | Health & social care | 2017 |
| Jeremy Symonds Properties Limited | Extraterritorial | 2009 |
| Jerl Enterprises Limited | Real estate | 1975 |
| Jesse and Jeron Services Ltd | Extraterritorial | 2025 |
| JF Dairies Ltd | Other services | 2020 |
| JFC Estates Limited | Real estate | 2024 |
| JFL Roofing Ltd | Construction | 2025 |
| Jjid Care Holdings Limited | Wholesale & retail | 2025 |
| Jjjn Homes Ltd | Real estate | 2023 |
| Jksn Ltd | Wholesale & retail | 2018 |
| JLC Drafting Ltd | Professional & scientific | 2021 |
| Jlds Limited | Information & communication | 2002 |
| JLW Electrical Solutions Limited | Construction | 2024 |
| JM 14 Healthcare Limited | Health & social care | 2016 |
| JMB Multi Services Ltd | Administrative & support | 2023 |
| JNC Executive Travel Ltd | Transport & logistics | 2013 |
| JNH Scaffolding Limited | Construction | 2020 |
| Joel Richmond Limited | Professional & scientific | 2010 |
| John and Mark Ltd | Education | 2021 |
| John and Smith Fashion Ltd | Wholesale & retail | 2020 |
| John and Smith Ltd | Information & communication | 2015 |
| John and Smith Properties Ltd | Real estate | 2022 |
| John Beattie Plumbing and Heating Engineers Limited | Construction | 1990 |
| John Burton & Sons Limited | Manufacturing | 2003 |
| John Hall Financial Services Limited | Financial services | 2019 |
| John Harman Thatching Limited | Construction | 2012 |
| John Rand Consultancy Limited | Professional & scientific | 2016 |
| John Swain Holdings Limited | Professional & scientific | 2009 |
| John Swain Limited | Agriculture & fishing | 1918 |
| Johnsons Courtyard Management Limited | Households | 1998 |
| Joint Staffing Solutions HC Ltd | Administrative & support | 2021 |
| Jokerboy Limited | Arts & recreation | 2025 |
| JON Haiselden Ltd | Professional & scientific | 2025 |
| Jones Building Group Limited | Financial services | 2013 |
| Jones Developments (South West) Limited | Extraterritorial | 2017 |
| Jones East 8 LLP | | 2024 |
| Jones Homes (South West) Limited | Extraterritorial | 2017 |
| Jones's Homes Ltd | Real estate | 2025 |
| Jordan Construction (South West) Limited | Construction | 2013 |
| Journeys by Miranda Ltd | Administrative & support | 2021 |
| Joyall Ltd | Information & communication | 2020 |
| JP Creative Emporium Limited | Professional & scientific | 2012 |
| JRS Construction Services Ltd | Administrative & support | 2009 |
| JS & Partners Limited | Real estate | 2018 |
| JS Group of Companies Ltd | Wholesale & retail | 2024 |
| JS Property Makeover Limited | Real estate | 2019 |