| JIE Investments Limited | Real estate | 2023 |
| Jigsaw Creative Care Limited | Administrative & support | 2000 |
| Jilted Generation Productions Ltd | Information & communication | 2022 |
| JIM Johnston Photography Ltd | Professional & scientific | 2012 |
| Jironah Support Limited | Health & social care | 2025 |
| JJ Agrifert Ltd | Agriculture & fishing | 2024 |
| JJB Watches Ltd | Wholesale & retail | 2022 |
| JJK Cleaning & Guttering Limited | Other services | 2013 |
| Jjpk Limited | Wholesale & retail | 2025 |
| JJS SW Holdings Ltd | Financial services | 2024 |
| JK Building & Refurbishments Ltd | Construction | 2021 |
| JK Grounds Maintenance Ltd | Administrative & support | 2026 |
| JK Property (Truro) Ltd | Real estate | 2010 |
| JK Property (Yelverton) Limited | Financial services | 2017 |
| JK26 Fashion Ltd | Wholesale & retail | 2026 |
| JLC Legal Ltd | Professional & scientific | 2020 |
| Jlocumservices Limited | Health & social care | 2012 |
| JLW Investments Ltd | Financial services | 2023 |
| JM Autos (Taunton) Ltd | Wholesale & retail | 2017 |
| JM Couriers Ltd | Transport & logistics | 2010 |
| JM Game Holdings Limited | Financial services | 2024 |
| JM Game Limited | Agriculture & fishing | 2021 |
| Jmac Project Ltd | Other services | 2025 |
| JME3 Limited | Health & social care | 2021 |
| JMJ Snow Limited | Arts & recreation | 2014 |
| JMR Home Improvements Ltd | Construction | 2020 |
| JMS Dental Laboratory Limited | Health & social care | 2006 |
| Jmvm Holding Group Ltd | Other services | 2020 |
| JMW (UK) Limited | Professional & scientific | 1994 |
| JNA Developments Limited | Construction | 2006 |
| Jncl Training UK Ltd | Education | 2025 |
| Jnjsoft Ltd | Information & communication | 2025 |
| Joanna Matravers Bar and Catering Limited | Hospitality | 2024 |
| JOE Falder Ltd | Financial services | 2023 |
| Johannsen Properties Limited | Real estate | 2015 |
| John and Jill Limited | Financial services | 1973 |
| John Beaufoy Publishing Limited | Information & communication | 2008 |
| John Care and Support Ltd | Health & social care | 2017 |
| John Condliffe Ltd | Professional & scientific | 2022 |
| John Douglas Estates Ltd. | Real estate | 1987 |
| John F. Mcfadden Limited | Construction | 2000 |
| John Gower Consulting Limited | Professional & scientific | 2014 |
| John Henden Consultancy Limited | Health & social care | 2003 |
| John Hodgins Mortgage Solutions Limited | Financial services | 2008 |
| John Saumarez Smith Limited | Wholesale & retail | 2008 |
| John Short Studio Ltd | Administrative & support | 2008 |
| John Vessey & Sons Limited | Professional & scientific | 1920 |
| Johnny's Eats Limited | Hospitality | 2025 |
| Jointmay Limited | Professional & scientific | 1980 |
| Jojopa Limited | Professional & scientific | 2015 |
| Jolly Automotive Property Services Ltd | Professional & scientific | 2019 |
| JON Pitts Limited | Administrative & support | 2008 |
| JON West Trading Limited | Wholesale & retail | 2011 |
| Jonathan Ball Consultancy Limited | Professional & scientific | 2024 |
| Jones Chiropractic Limited | Health & social care | 2007 |
| Jones Crenshaw Andrews Ltd | Arts & recreation | 2018 |
| Jonics (UK) Limited | Information & communication | 2007 |
| Joojeme Medical Limited | Health & social care | 2021 |
| Josca Ltd | Professional & scientific | 2015 |
| Josh Jones Film Services Limited | Information & communication | 2007 |
| Josh Venn Motors Limited | Wholesale & retail | 2018 |
| Joshua Flower Export Ltd | Wholesale & retail | 2025 |
| Joyce Afro-Caribbean Foods Ltd | Wholesale & retail | 2024 |
| Joyful Services Limited | Administrative & support | 2019 |
| JP Justin George Limited | Health & social care | 2021 |
| JP Rata Ltd | Professional & scientific | 2013 |
| JPL Contractors Ltd | Manufacturing | 2021 |
| JPS Fashion Ltd | Wholesale & retail | 2012 |
| JPW Paint and Body Repairs Limited | Wholesale & retail | 2023 |
| JR Fowler GAS Services Limited | Construction | 2019 |
| JR Payroll South West Ltd | Professional & scientific | 2020 |
| JR Urology Limited | Health & social care | 2015 |
| Jrea Ltd | Real estate | 2021 |
| JRF Farms Ltd | Agriculture & fishing | 2026 |
| JRF Holdings Ltd | Financial services | 2026 |
| JRL Management Limited | Other services | 2007 |
| JRM Retail Group Ltd | Wholesale & retail | 2024 |
| JRP Accountancy Ltd | Professional & scientific | 2013 |
| JS Construction South West Limited | Construction | 2018 |
| Jsbusinesstransformation Ltd | Administrative & support | 2024 |
| Jsgextinguishers Ltd | Public administration | 2024 |
| JSJ Plant Services Limited | Construction | 2009 |
| Jsnh Limited | Real estate | 2022 |
| JSR Utilities Ltd | Construction | 2026 |
| JT & AJ Andrews Limited | Agriculture & fishing | 2011 |
| JTC III Limited | Financial services | 2018 |
| JTP Property Services Ltd | Real estate | 2025 |
| Jubilee Gardens (Banwell) Management Company Limited | Households | 2023 |
| Julian Burrows Limited | Professional & scientific | 2007 |
| Julian LAY Properties Limited | Real estate | 2020 |
| Junction 22 Trailers Ltd | Other services | 2020 |
| Juniper Grove | Financial services | 2023 |
| Juno Holding Group Ltd | Financial services | 2025 |
| Juno Space Ltd | Hospitality | 2020 |
| Jupiter Aviation Consultancy Ltd | Professional & scientific | 2024 |
| Jurgens Beheer Limited | Professional & scientific | 2005 |
| Just Scale Growth Limited | Professional & scientific | 2025 |
| JVA Management Ltd | Real estate | 2022 |
| JVL Plumbing & Heating Limited | Construction | 2024 |
| JW Building Services Limited | Construction | 2019 |