| Jelos Limited | Real estate | 2013 |
| Jelp Money LLP | | 2023 |
| JEM Recycling Limited | Water & waste | 1995 |
| JEM Spray Limited | Transport & logistics | 2026 |
| Jemglobal Ltd | Other services | 2023 |
| Jemico Cyfyngedig | Professional & scientific | 2014 |
| Jemma Collins Dermatology Ltd | Health & social care | 2024 |
| Jemsar Engineering Ltd | Professional & scientific | 2012 |
| Jemsar Group Limited | Financial services | 2020 |
| Jemsar People Limited | Administrative & support | 2023 |
| Jen's Nails Ltd | Other services | 2021 |
| Jenavin Ltd | Real estate | 2018 |
| Jenbar Properties Ltd | Real estate | 2023 |
| Jenc Healthessence Limited | Health & social care | 2025 |
| Jencap Consulting Ltd | Financial services | 2007 |
| Jencap Partners Ltd | Professional & scientific | 2020 |
| Jenco Developments Limited | Construction | 2000 |
| Jenelle Natural Health Limited | Health & social care | 2012 |
| Jenesys HQ Ltd | Information & communication | 2022 |
| Jenkins Best Limited | Real estate | 2018 |
| Jenkins Eye-Surgery Ltd | Health & social care | 2018 |
| Jenkins Locum and Admin Limited | Health & social care | 2003 |
| Jenkins Medical Reports Limited | Professional & scientific | 2010 |
| Jenkins Porch & Partners Limited | Professional & scientific | 2005 |
| Jenlec Limited | Construction | 2019 |
| Jennicks Limited | Professional & scientific | 2022 |
| Jennifer Santos Ltd | Health & social care | 2020 |
| Jennings Belgravia Consultancy Limited | Professional & scientific | 2025 |
| Jennings Weston and Bricknell Ltd | Construction | 2024 |
| Jennison Logistics Limited | Professional & scientific | 2019 |
| Jenny Ashton Consultancy Ltd | Professional & scientific | 2026 |
| Jenny Dafydd Media Ltd | Manufacturing | 2023 |
| Jentech Limited | Professional & scientific | 2018 |
| Jenuko Ltd | Wholesale & retail | 2018 |
| JEP Estates Limited | Real estate | 2004 |
| Jeppo Limited | Real estate | 2022 |
| Jeremy Sandbrook Medico-Legal Limited | Health & social care | 2023 |
| Jerolizz Ltd | Wholesale & retail | 2024 |
| Jerry and Jerry Services Ltd | Construction | 2019 |
| Jerry Bradshaw Ltd | Manufacturing | 2024 |
| Jert Ltd | Real estate | 2021 |
| Jerusalem Limited | Information & communication | 2025 |
| Jerusalem Treaty Organisation Limited | Professional & scientific | 2015 |
| Jervis Coaches Limited | Transport & logistics | 2005 |
| JES the Girl Powder Ltd | Wholesale & retail | 2026 |
| Jesaa Investments Limited | Real estate | 2002 |
| Jesbrow Limited | Real estate | 1976 |
| Jeskelo Recruits Ltd | Wholesale & retail | 2021 |
| Jesko Frames Limited | Information & communication | 2025 |
| Jesmin Properties LLP | | 2023 |
| Jespad Limited | Real estate | 2021 |
| Jess Entertainment Ltd | Wholesale & retail | 2018 |
| Jessa Enterprises Ltd | Construction | 2015 |
| Jesse T Homes Ltd | Real estate | 2025 |
| Jessicadenning CYF | Wholesale & retail | 2025 |
| Jessie Hallett Social Ltd | Professional & scientific | 2023 |
| Jessopp's Tree Services Ltd | Agriculture & fishing | 2023 |
| Jesusmary Ltd | Construction | 2018 |
| JET Force One Ltd | Administrative & support | 2025 |
| JET Funding Limited | Administrative & support | 2019 |
| JET Import Belgium PLC | Professional & scientific | 2007 |
| JET Property Cardiff Limited | Real estate | 2021 |
| JET SKI Rentals - Ibiza Ltd | Administrative & support | 2024 |
| JET Spanner Ltd | Manufacturing | 2011 |
| JET Star Management Ltd | Hospitality | 2019 |
| JET TV Limited | Arts & recreation | 2017 |
| Jetblazeit Ltd | Information & communication | 2025 |
| Jetclub Management Ltd | Transport & logistics | 2024 |
| Jethiwaq Mart Ltd | Wholesale & retail | 2025 |
| Jethrik Productions Ltd | Information & communication | 2026 |
| Jethro Financial Management Ltd | Professional & scientific | 2017 |
| Jethro Logistics Ltd | Transport & logistics | 2017 |
| Jetmedia Group PC | | 2018 |
| Jetray Limited | Wholesale & retail | 2020 |
| Jetting Systems Ltd | Manufacturing | 2003 |
| Jettyhead Limited | Wholesale & retail | 2026 |
| Jeur Letting Limited | Real estate | 2015 |
| Jeur Realies & Investments Limited | Real estate | 2018 |
| Jewedoly Ltd | Manufacturing | 2023 |
| Jewel in Nook Ltd | Manufacturing | 2024 |
| Jewelever Limited | Wholesale & retail | 2010 |
| Jewellita Ltd | Wholesale & retail | 2025 |
| Jewels Canley Interiors Ltd | Wholesale & retail | 2007 |
| Jewels Travel & Hospitality Recruitment Ltd | Administrative & support | 2018 |
| Jewelsbyvania Ltd | Manufacturing | 2024 |
| Jeyna Food and Beverages Ltd | Hospitality | 2018 |
| Jezd Design Studio Ltd | Professional & scientific | 2019 |
| JF & DF Construction Ltd | Construction | 2024 |
| JF Contraction Ltd | Construction | 2025 |
| JF Golf Limited | Arts & recreation | 2013 |
| JF Medical Limited | Health & social care | 2018 |
| JF Transportation Ltd | Transport & logistics | 2025 |
| JFC Properties Ltd | Real estate | 2018 |
| JFM Business Advisers Limited | Professional & scientific | 2003 |
| JFM Holdings Limited | Real estate | 2007 |
| JFR Developments Limited | Real estate | 2016 |
| JFR Equipment Limited | Professional & scientific | 2018 |
| Jfurreed Property Network Ltd | Real estate | 2024 |
| JG Consulting Solutions Ltd | Real estate | 2025 |
| JG Educate Ltd | Education | 2019 |