| Johnson's (Insulation) Supplies Limited | Construction | 1983 |
| Johnson's Insulation Hampshire Limited | Construction | 2016 |
| Johnson's Insulation Kent Limited | Construction | 2016 |
| Jones Building Supplies and Waste Limited | Water & waste | 2025 |
| Joseph Caruana Limited | Wholesale & retail | 2002 |
| Joshua Wine Limited | Wholesale & retail | 2024 |
| Jostim Limited | Administrative & support | 2018 |
| JP Broadcast Engineering Limited | Information & communication | 2016 |
| JP Building Supplies Ltd | Construction | 2023 |
| JP Pumps and Drainage Ltd | Water & waste | 2022 |
| JPC Ventures Ltd | Professional & scientific | 2025 |
| JPZ Resinpro Surfaces Ltd | Construction | 2025 |
| JPZ Tree Care & Landscaping Ltd | Administrative & support | 2023 |
| JR FFF Coaching LLP | | 2025 |
| JR Retail Limited | Wholesale & retail | 2026 |
| JRP Building Contractors Ltd | Extraterritorial | 2024 |
| JS Protection Group Ltd | Administrative & support | 2026 |
| JS Sussex Ltd | Construction | 2014 |
| JSB Autocare Mobile Mechanic Ltd | Professional & scientific | 2025 |
| JT Vineyard Holdings Ltd | Agriculture & fishing | 2026 |
| Jtkefx Limited | Information & communication | 2011 |
| Julie Aldridge Consulting Ltd | Professional & scientific | 2016 |
| Jump PR Ltd | Administrative & support | 2003 |
| Jumpinfun Eastboune Ltd | Hospitality | 2025 |
| Jumpinfun Events Ltd | Administrative & support | 2023 |
| Jumpinfun Paymaster Ltd | Professional & scientific | 2025 |
| Jumpinfun Rochester Ltd | Hospitality | 2024 |
| Jumpinfun Salisbury Ltd | Hospitality | 2024 |
| Jurial Construction Limited | Construction | 2004 |
| Jurial Home Limited | Construction | 2022 |
| Just Metal UK Limited | Manufacturing | 2009 |
| JWP Lifestyle Coaching Limited | Other services | 2020 |
| K & R Parsons Limited | Construction | 2019 |
| K J Thorne Butchers Limited | Wholesale & retail | 2020 |
| K Q Touring Productions Limited | Arts & recreation | 2012 |
| K Smith Fast Foods Limited | Professional & scientific | 2010 |
| K V Manufacturing Limited | Manufacturing | 2014 |
| K Virgo Plumbing & Heating Ltd | Other services | 2012 |
| Kaeser Compressors Ltd | Professional & scientific | 1997 |
| Kaipability Ltd | Professional & scientific | 2024 |
| Kalliz Limited | Health & social care | 2015 |
| KAN Haulage Limited | Water & waste | 2024 |
| Kanal Ltd | Wholesale & retail | 2025 |
| Kangaroo Consulting Ltd. | Professional & scientific | 2013 |
| Karpe Diem Healthcare Ltd | Health & social care | 2018 |
| Kaycee Roofing Limited | Construction | 1995 |
| Kazina Property Ltd | Real estate | 2023 |
| Kazi’S Curry Mahal Ltd | Hospitality | 2024 |
| KCL Management Services Limited | Professional & scientific | 1998 |
| KDG Management Limited | Professional & scientific | 2021 |
| Kdlc Investment Group Limited | Financial services | 2025 |
| Kdlc Property Group Limited | Real estate | 2025 |
| Keats House (Management) Ltd. | Households | 2002 |
| Keisai UK Ltd | Wholesale & retail | 2024 |
| Keith Harris & Associates Limited | Professional & scientific | 1999 |
| Keith Hooker Consultants Limited | Construction | 2011 |
| Keke Media Ltd | Professional & scientific | 2023 |
| Kelly's Facilities Management Ltd | Water & waste | 2019 |
| KEN Johnstone (Steyning) Limited | Real estate | 1958 |
| Kenley Care Ltd | Health & social care | 2014 |
| Kerz Solutions Ltd | Health & social care | 2019 |
| Key Casting Limited | Administrative & support | 2016 |
| Key Twelve Ltd | Wholesale & retail | 2018 |
| KEY18 Limited | Real estate | 2017 |
| Keymer Double Glazing Ltd. | Manufacturing | 1991 |
| Keymer Haslam Wealth Management Ltd | Financial services | 2025 |
| Keymer Place Management Company Ltd | Real estate | 2015 |
| Keymer Property Services Ltd | Real estate | 2014 |
| Keystone GRP Limited | Professional & scientific | 2026 |
| KGB Commerce Ltd | Wholesale & retail | 2026 |
| Kinego Limited | Information & communication | 2006 |
| King Brothers (Finance) Limited | Wholesale & retail | 1976 |
| King's Trading Limited | Hospitality | 2017 |
| Kings Barn Limited | Other services | 2005 |
| Kingsmead Place Management Company Limited | Households | 1999 |
| Kingswell Roofing Ltd | Construction | 2023 |
| Kitbag Hire Ltd | Administrative & support | 2010 |
| KJ Commerce Ltd | Wholesale & retail | 2026 |
| KJ Murray Estates Ltd | Real estate | 2025 |
| KLA HR Ltd | Administrative & support | 2025 |
| Klaranova Ltd | Education | 2023 |
| KMB Automotive Ltd | Wholesale & retail | 2019 |
| Knights Prestige Transport Ltd | Transport & logistics | 2024 |
| Knyveton Court Flats 1-9 (Burgess Hill) RTM Company Limited | Real estate | 2010 |
| Knyveton Court Flats 10-28 (Burgess Hill) RTM Company Limited | Real estate | 2010 |
| KPA Management Consultancy Ltd | Professional & scientific | 2022 |
| KPG Products Ltd | Manufacturing | 2002 |
| Krafted Surface Designs Limited | Construction | 2022 |
| KRD Media Limited | Information & communication | 2017 |
| KTI Therapies Limited | Other services | 2015 |
| Kudu Home Solutions Ltd | Construction | 2017 |
| KUN Services Ltd | Transport & logistics | 2026 |
| Kurt Electrical Limited | Construction | 2017 |
| Kyneton Lodge RTM Company Limited | Households | 2024 |
| L & T Projects Limited | Construction | 2012 |
| L R Landscapes Ltd | Administrative & support | 2019 |
| L Windham Painting Contractors Ltd | Construction | 2008 |
| L&H Essentials Ltd | Wholesale & retail | 2026 |
| L.M. Associates Limited | Professional & scientific | 1999 |
| Laap Concepts Limited | Manufacturing | 2011 |