| Israr Limited | Other services | 2007 |
| It's Your Designer Ltd | Professional & scientific | 2020 |
| Iticp Ltd | Information & communication | 2025 |
| IUN Consult Limited | Health & social care | 2023 |
| Ivoa Ltd | Administrative & support | 2026 |
| IVY Lodge Management Limited | Real estate | 2018 |
| IWC Technical Solutions Ltd | Professional & scientific | 2018 |
| Iwealth Holdings Limited | Financial services | 2017 |
| IZ Oral Healthcare Ltd | Health & social care | 2007 |
| Izen Healthcare Limited | Health & social care | 2023 |
| J & P Estates Ltd | Households | 2018 |
| J a Medical Services (Altrincham) Ltd | Health & social care | 2013 |
| J C Consulting 360 Ltd | Information & communication | 2017 |
| J Casey Property Ltd | Real estate | 2025 |
| J D Cooney Limited | Construction | 2003 |
| J D Morgan Limited | | 2002 |
| J Fallon Commercial Consultants Ltd | Professional & scientific | 2017 |
| J J Forecourts Ltd | Wholesale & retail | 2024 |
| J Jones T/A R T Jones Ltd | Professional & scientific | 2003 |
| J Layton Sales Ltd | Wholesale & retail | 2024 |
| J M Decorators Ltd | Construction | 2014 |
| J O Omofuma Limited | Health & social care | 2008 |
| J R Design and Decorating Ltd | Construction | 2022 |
| J R S Fabrications Ltd | Administrative & support | 2006 |
| J Samuel Consultancy Ltd | Education | 2026 |
| J Starr Properties Ltd | Real estate | 2021 |
| J Weston Homes Ltd | Real estate | 2021 |
| J Yearn Property Investments Ltd | Financial services | 2024 |
| J&C Corner Cafe Limited | Hospitality | 2026 |
| J&L Almond Pubs Ltd | Hospitality | 2024 |
| J. M. E. Transport Limited | Transport & logistics | 1982 |
| J.A.P.E. LLP | | 2018 |
| J.M.Jees Limited | Hospitality | 2014 |
| J.P.C Construction and Groundworks Ltd | Construction | 2015 |
| Jabstone Limited | Real estate | 2025 |
| Jackedfruit C.I.C. | Arts & recreation | 2026 |
| Jackie Takeaway Limited | Hospitality | 2018 |
| Jackson Agencies Limited | Households | 2014 |
| Jackstone CS Limited | Professional & scientific | 2017 |
| Jacob Austin Ltd | Real estate | 2021 |
| Jadon Limited | Wholesale & retail | 2020 |
| James Cadman Screeding (N/W) Limited | Construction | 2008 |
| Jamiesons DRY Cleaners Limited | Administrative & support | 2015 |
| Jamville One Ltd | Real estate | 2025 |
| Janus HR Consult Ltd | Professional & scientific | 2020 |
| JAS & Co Accountants Ltd | Professional & scientific | 2023 |
| Javell Lynton Carty Limited | Professional & scientific | 2024 |
| JAY24 Support Ltd | Health & social care | 2021 |
| Jayb Fabrication Engineering Limited | Manufacturing | 2017 |
| Jays Storage Ltd | Other services | 2014 |
| Jayvee Building Services Limited | Construction | 2009 |
| JB Aesthetics MCR Ltd | Extraterritorial | 2023 |
| Jbbm Properties Ltd | Real estate | 2023 |
| JBG Grace Properties Ltd | Real estate | 2026 |
| JC Accountancy & Taxation Services Limited | Professional & scientific | 2023 |
| JC Advisory & Consulting Limited | Professional & scientific | 2016 |
| JCA Advisory Enterprises Limited | Manufacturing | 2017 |
| JCG Financials Limited | Professional & scientific | 2014 |
| JCS Cleaning Solutions Limited | Administrative & support | 2020 |
| JCS Marketing Ltd | Professional & scientific | 2022 |
| JD Scaffolds Ltd | Construction | 2024 |
| JDH Wealth Ltd | Professional & scientific | 2015 |
| JDI - Digital Transform Ltd | Information & communication | 2024 |
| Jefferies EXP Limited | Administrative & support | 2010 |
| JEK House Ltd | Real estate | 2020 |
| JEM UK Ltd | Wholesale & retail | 2008 |
| Jemap LLP | | 2006 |
| Jennings Avenue Ltd | Real estate | 2022 |
| Jesanel Kaye Ltd | Health & social care | 2017 |
| Jetso Limited | Professional & scientific | 2023 |
| Jevons and Siddall Limited | Health & social care | 2008 |
| JF Optometry Ltd | Health & social care | 2019 |
| JFM CDM Advisors Ltd | Other services | 2016 |
| Jhharding Planning Limited | Construction | 2019 |
| Jhsa Holdings Ltd | Financial services | 2024 |
| JI Property Investments Ltd | Real estate | 2024 |
| Jimmy Fairhurst Projects Limited | Administrative & support | 2025 |
| Jinhao Construction Ltd | Construction | 2025 |
| JIO Investments Limited | Real estate | 2024 |
| JJ Painting Services Limited | Construction | 2023 |
| JJ Structures Ltd | Professional & scientific | 2020 |
| JJD Commercial Services Ltd | Professional & scientific | 2026 |
| JJE Trading Ltd | Wholesale & retail | 2026 |
| JJM Creative Ltd | Professional & scientific | 2020 |
| JJM Harris Ltd | Real estate | 2020 |
| JJP Airputha Ltd | Real estate | 2024 |
| JJW Business Consulting Limited | Professional & scientific | 2023 |
| JKM IT Solutions Limited | Information & communication | 2017 |
| JKS Plastic Collections Ltd | Water & waste | 2020 |
| JKV Incorporation Limited | Financial services | 2012 |
| JL GP Ltd | Health & social care | 2025 |
| JLB Beauty Ltd | Other services | 2021 |
| JM Data Services Ltd | Information & communication | 2026 |
| JMB Crossfit Limited | Arts & recreation | 2013 |
| Jmhe Ltd | Real estate | 2019 |
| JMI Psychological Services Limited | Administrative & support | 2016 |
| JNS Services Limited | Professional & scientific | 2024 |
| JO & Co. Brand Communications & Digital Strategy Ltd | Professional & scientific | 2017 |
| JO Sanderson Ltd | Administrative & support | 2022 |
| Joan Global Decor Ltd | Other services | 2020 |