| Itchy-Horse Company Ltd | Professional & scientific | 2013 |
| Itxtra Limited | Information & communication | 2015 |
| Iwan Thomas Farrier Ltd | Agriculture & fishing | 2015 |
| J & B Joinery Ltd | Construction | 2016 |
| J & C Surfacing Limited | Administrative & support | 2009 |
| J & K Contracting Limited | Construction | 2020 |
| J & T Surface Repairs Ltd | Other services | 2016 |
| J and M Clement-Evans & Sons Ltd | Extraterritorial | 2014 |
| J Bevan Properties Ltd | Real estate | 2025 |
| J C L Estates & Lettings Ltd | Real estate | 2023 |
| J D E Electrical Contractors Limited | Construction | 2002 |
| J D Owen Transport Services Limited | Transport & logistics | 2011 |
| J E & E J Davies Properties Limited | Real estate | 2010 |
| J F Campers Ltd | Manufacturing | 2024 |
| J J Sherwood Consultancy Limited | Professional & scientific | 2018 |
| J J Sherwood Lettings Limited | Hospitality | 2023 |
| J O Morris Groundworks Ltd | Construction | 2006 |
| J S Health and Safety Ltd. | Professional & scientific | 2013 |
| J S Transport N.Wales Ltd | Transport & logistics | 2024 |
| J&Nb Trading Limited | Construction | 2017 |
| J. Bradburne Price & Co Ltd | Wholesale & retail | 2023 |
| J.A GAS Services Ltd | Construction | 2020 |
| J.D.H. Business Services Limited | Professional & scientific | 1999 |
| J.R.M.B. Limited | Professional & scientific | 2018 |
| JAA Contracting Ltd | Construction | 2026 |
| Jackson (Fire & Security) Ltd | Public administration | 1999 |
| Jackson Fire & Security UK Ltd | Other services | 2013 |
| Jackson Hair Salon Limited | Other services | 2002 |
| Jackson Rentals Ltd | Real estate | 2024 |
| Jais Consulting Ltd | Professional & scientific | 2020 |
| JAL Roofing & Cladding Limited | Construction | 2020 |
| Jaltec Engineering Limited | Construction | 2014 |
| James Anthony Roofing Ltd | Construction | 2017 |
| James Willis Limited | Construction | 2025 |
| James-Paul Mcnally Limited | Extraterritorial | 2025 |
| Jasper Products Limited | Manufacturing | 2017 |
| Jays First Class Ltd | Transport & logistics | 2021 |
| JBS Catering Ltd | Hospitality | 2018 |
| JBW Electrical Solutions Limited | Construction | 2012 |
| JCE Properties Limited | Real estate | 2014 |
| JCL Contracting Limited | Real estate | 2021 |
| JCO Design Engineering Ltd | Professional & scientific | 2024 |
| Jcset Limited | Information & communication | 2025 |
| JCW Electrical Services Ltd | Construction | 2020 |
| JD Brown Plant and Machinery Limited | Wholesale & retail | 2023 |
| JD Company Services Limited | Professional & scientific | 2000 |
| JD Web Services Ltd | Wholesale & retail | 2018 |
| JFM Carpentry & Construction Limited | Construction | 2026 |
| JHD Accountancy Ltd | Professional & scientific | 2010 |
| Jigsaw Live Events Limited | Arts & recreation | 2008 |
| JJR Podiatry Ltd | Health & social care | 2025 |
| JJW Books Limited | Administrative & support | 2023 |
| JK Groundworks (NW) Ltd | Construction | 2017 |
| JKS Consulting Limited | Professional & scientific | 2006 |
| JMC Autohaus Ltd | Wholesale & retail | 2023 |
| JMC Cladding Ltd | Construction | 2026 |
| JMR Home Enhancements Ltd | Construction | 2020 |
| JN Physio Limited | Health & social care | 2025 |
| John Woods Motorcare Ltd | Wholesale & retail | 2017 |
| Johnson & Price Limited | Wholesale & retail | 2011 |
| Joint Effort CYF. | Hospitality | 2024 |
| Jolee Group Ltd | Wholesale & retail | 2022 |
| JON Bellis Ltd | Real estate | 2018 |
| Jonathan Fagan Business Brokers Limited | Professional & scientific | 2017 |
| Jones Brothers Leeswood Limited | Construction | 2013 |
| Jones Price Limited | Wholesale & retail | 2009 |
| JPS Systems Limited | Construction | 2009 |
| Jubilee Homes (Buckley) Limited | Construction | 2021 |
| Jubilee Homes (Management) Company Ltd | Real estate | 2022 |
| June Rose Estates Ltd | Real estate | 2026 |
| Just Financial Group NW Ltd | Financial services | 2020 |
| JW Davies Motors & Family Limited | Wholesale & retail | 2025 |
| K B OIL Ltd | Manufacturing | 2018 |
| K Hairco Ltd | Other services | 2016 |
| K L Care Limited | Health & social care | 2007 |
| Kajenta Limited | Wholesale & retail | 2008 |
| Karisma Barbers (Mold) Ltd | Other services | 2019 |
| Karisma Project Management Ltd | Construction | 2026 |
| Kasco Design Limited | Professional & scientific | 2011 |
| Kasthury Limited | Wholesale & retail | 2014 |
| Kate Maple Consultancy Ltd | Professional & scientific | 2021 |
| Katie Lynch Consultancy Limited | Professional & scientific | 2025 |
| KBO Systems Ltd | Professional & scientific | 2025 |
| Keane & Williams Property Ltd | Construction | 2026 |
| Keanes Holdings Limited | Real estate | 2023 |
| Keelbrook Holdings Limited | Wholesale & retail | 2024 |
| Kemaro Engineering Consultancy Limited | Professional & scientific | 2024 |
| Kensington Windows Ltd | Construction | 2011 |
| KEZ Domesti̇c & Commerci̇al Cleani̇ng Ltd | Administrative & support | 2025 |
| KGJ Mechanical Services Limited | Administrative & support | 2009 |
| Kickstart Project Management Ltd | Professional & scientific | 2019 |
| Kilan Stud CYF | Agriculture & fishing | 2018 |
| Kings Oak Farm Ltd | Agriculture & fishing | 2019 |
| Kinnico Ltd | Professional & scientific | 2020 |
| Kln-Technology Ltd | Information & communication | 2022 |
| KMA Tool Hire & Sales Ltd | Administrative & support | 2017 |
| KMT Domestic Management Limited | Administrative & support | 2024 |
| Knight Shadow Ltd | Information & communication | 2021 |
| Knowledgesourcehr UK Ltd | Administrative & support | 2011 |
| Koala Catering Ltd | Hospitality | 2018 |