| Janois Ltd | Wholesale & retail | 2023 |
| Janova Solutions Limited | Information & communication | 2025 |
| Japan System Planning (U.K) Ltd. | Wholesale & retail | 2004 |
| Japanese Knotweed Management Services Ltd | Water & waste | 2016 |
| Jardine Family Holdings Limited | Financial services | 2023 |
| Jarek Sawicki Enterprises Ltd | Financial services | 2022 |
| Jasguru Limited | Health & social care | 2018 |
| Jask Holdings Limited | Real estate | 2025 |
| Jasmincrest Limited | Real estate | 1995 |
| Jasmine IP33 Ltd | Hospitality | 2023 |
| Jasohm Holdings Limited | Financial services | 2018 |
| Jason Hughes Brickwork Limited | Construction | 2001 |
| Jason Jestin Ltd | Education | 2019 |
| Jason Parker Coaching Ltd. | Education | 2025 |
| Jasons Cars Ltd | Wholesale & retail | 2026 |
| Jassian Group Limited | Administrative & support | 2025 |
| Jawl Services Ltd | Construction | 2023 |
| JAY Accounting Services Ltd | Professional & scientific | 2020 |
| JAY Cleaning Services Ltd | Administrative & support | 2025 |
| JAY Spice Limited | Professional & scientific | 2003 |
| Jayben Services Limited | Wholesale & retail | 2017 |
| Jaysm Limited | Professional & scientific | 2020 |
| Jaytam Limited | Health & social care | 2015 |
| JB Biomass Limited | Wholesale & retail | 2020 |
| JB Sports Limited | Arts & recreation | 2015 |
| JB Van Hire Ltd | Administrative & support | 2025 |
| JB Waterproofing Limited | Construction | 2019 |
| JBC Accountancy Solutions Ltd | Professional & scientific | 2020 |
| JBC Enterprises Limited | Professional & scientific | 2017 |
| Jbfd Ltd | Professional & scientific | 2006 |
| JBH Investment Group Ltd | Construction | 2025 |
| JBM Services Contractors Ltd | Construction | 2022 |
| JBS and Webb Limited | Administrative & support | 2017 |
| JBS Property Investment Ltd | Real estate | 2024 |
| JC Digital Studio Ltd | Information & communication | 2026 |
| JC Finance Advisory Limited | Professional & scientific | 2025 |
| JC Surgical Ltd | Health & social care | 2020 |
| Jcad Ltd | Professional & scientific | 2019 |
| JCB Trading Limited | Wholesale & retail | 2017 |
| JCC Products Ltd | Manufacturing | 2025 |
| JCE Control & Electrical Services Limited | Construction | 2020 |
| JCL Ed-Al Limited | Wholesale & retail | 2020 |
| Jcmufx Ltd | Financial services | 2025 |
| Jcobley Opsco Limited | Professional & scientific | 2026 |
| JCV Developments Ltd | Construction | 2023 |
| JD Byford Ltd | Professional & scientific | 2019 |
| JD Labs Ltd | Information & communication | 2026 |
| JDA Digital Limited | Information & communication | 2024 |
| Jdb-Net Limited | Information & communication | 2026 |
| JDG Motor Services Ltd | Wholesale & retail | 2017 |
| JDL Connect Limited | Professional & scientific | 2023 |
| JDM Travel Ltd | Administrative & support | 2025 |
| JDR International Limited | Other services | 2021 |
| JE Miller Accountancy & Taxation Services Limited | Professional & scientific | 2009 |
| Jecity.Net Limited | Information & communication | 2010 |
| Jeempoint Ltd | Wholesale & retail | 2025 |
| Jeevaani Holdings Limited | Financial services | 2021 |
| Jeevaani New Earth Limited | Real estate | 2021 |
| Jeevaani Properties Limited | Real estate | 2015 |
| Jeffery Group Holdings Limited | Extraterritorial | 2017 |
| Jekalo Leisure Limited | Administrative & support | 2023 |
| Jelida Consulting Limited | Professional & scientific | 2012 |
| Jelly Beans Montessori Nursery Limited | Education | 2012 |
| JEM HR Ltd | Information & communication | 2022 |
| JEM Property Rental Ltd | Real estate | 2025 |
| Jennifer Bags Ltd | Wholesale & retail | 2025 |
| Jenny Sloneem CNS Limited | Health & social care | 2024 |
| Jenson Estates Ltd | Real estate | 2017 |
| Jentix Ltd | Information & communication | 2025 |
| Jeremiah Enterprise Ltd | Administrative & support | 2015 |
| Jeremiah Strategy LAB Ltd | Professional & scientific | 2025 |
| JEREMIAH616PRESS Ltd | Information & communication | 2025 |
| Jeremy Head Environmental Consulting Limited | Professional & scientific | 2019 |
| Jerk Haus Ltd | Hospitality | 2025 |
| Jermy & Hunt Carpentry Contractors Limited | Construction | 2007 |
| Jerrard Properties Limited | Real estate | 2025 |
| Jess Old Coaching Limited | Other services | 2024 |
| Jesse Consulting Limited | Professional & scientific | 2024 |
| Jessie Song Studio Ltd | Information & communication | 2026 |
| Jetsnext Ltd | Information & communication | 2023 |
| Jfrail Consulting Ltd | Transport & logistics | 2020 |
| JG Estates Ltd | Households | 2024 |
| JGR Holdings Ltd | Information & communication | 2025 |
| Jgreycodes Ltd | Information & communication | 2021 |
| JH Cable Services Ltd | Construction | 2025 |
| Jham Property Ltd | Real estate | 2021 |
| JHF Exterior Cleaning Ltd | Administrative & support | 2026 |
| Jiav Ltd | Transport & logistics | 2021 |
| Jidex Global Limited | Real estate | 2026 |
| Jigsaw Home Improvements Ltd | Construction | 2021 |
| Jimmys Dish Ltd | Hospitality | 2025 |
| Jinduoduo Limited | Wholesale & retail | 2026 |
| Jinlibiz Limited | Wholesale & retail | 2026 |
| Jistrite Ltd | Wholesale & retail | 2024 |
| JJ Auto Recovery & Logistics Ltd | Transport & logistics | 2026 |
| JJ Car Movements Ltd | Transport & logistics | 2024 |
| JJ Customs Solutions UK Ltd | Wholesale & retail | 2019 |
| JJ Empire Properties Limited | Real estate | 2025 |
| Jjdp Holdings Ltd | Real estate | 2021 |
| JJJ Content Services Ltd | Manufacturing | 2025 |