| Johnson Stanley Limited | Information & communication | 2019 |
| Johnston Education Consultancy Ltd | Education | 2022 |
| Jojems Ltd | Manufacturing | 1986 |
| Jojo Rainbow Ltd | Arts & recreation | 2013 |
| JOL Electrical Ltd | Construction | 2020 |
| Jolliepopz Ltd | Arts & recreation | 2026 |
| Jolly Forest Garden CIC | Other services | 2025 |
| Jolly Moon Ltd | Other services | 2021 |
| Jones & Sons Ventures Limited | Real estate | 2017 |
| JOR Groundworks and Driveways Ltd | Construction | 2024 |
| Joss Stoddart Limited | Manufacturing | 2022 |
| Journal of Pediatric Urology | Information & communication | 2004 |
| Joyful Minds Limited | Administrative & support | 2024 |
| JPD Finance Limited | Financial services | 1998 |
| Jpel Limited | Construction | 2012 |
| JPK Connect Ltd | Wholesale & retail | 2025 |
| JPM Rural Services Limited | Information & communication | 2017 |
| Jpma Consulting Limited | Professional & scientific | 2019 |
| JPS Group Limited | Financial services | 2018 |
| JPS Plumbing (Winchester) Limited | Construction | 2014 |
| JPS Property Investments Limited | Financial services | 2019 |
| Jqtech Limited | Information & communication | 2012 |
| JRB NO1 Limited | Other services | 2022 |
| JRB NO2 Ltd | Other services | 2025 |
| JRK Asset Management Ltd | Real estate | 2023 |
| JRP Farming Limited | Agriculture & fishing | 2010 |
| JRP Storage Limited | Manufacturing | 2022 |
| JS Roofing & Cladding Limited | Construction | 2015 |
| JS Vending Limited | Wholesale & retail | 2025 |
| JS3DM Limited | Professional & scientific | 2020 |
| Jskl Ltd | Construction | 2010 |
| JT Mechanical Ltd | Construction | 2015 |
| JTL Traders Ltd | Wholesale & retail | 2025 |
| Julian MAN Ltd | Manufacturing | 2013 |
| Junior Cars UK Limited | Manufacturing | 2025 |
| Juniper House Ltd. | Professional & scientific | 2012 |
| Juniper House Systems Ltd. | Information & communication | 1998 |
| Jura Consulting Limited | Professional & scientific | 2016 |
| Jurit LLP | | 2013 |
| Just a Little Bester Limited | Education | 2019 |
| Just ADD Hot Water Limited | Information & communication | 2016 |
| Just BRU Ltd | Wholesale & retail | 2020 |
| Just Ears Hearing Ltd | Health & social care | 2022 |
| Just Family Law Limited | Professional & scientific | 2013 |
| Just One More Hidden GEM Limited | Households | 2021 |
| Just One More Property Limited | Real estate | 2014 |
| Just Pleachy Ltd | Wholesale & retail | 2024 |
| Justbalance UK Limited | Information & communication | 2015 |
| Justice Jewellers Limited | Wholesale & retail | 2012 |
| JVH Enterprises Ltd | Hospitality | 2025 |
| JVM Consulting Ltd | Information & communication | 2006 |
| JW Architecture Ltd | Professional & scientific | 2020 |
| JW Iopening Projects Limited | Professional & scientific | 2018 |
| JWD Care Limited | Professional & scientific | 2010 |
| Jwrc Consulting Ltd | Professional & scientific | 2025 |
| Jyni Limited | Extraterritorial | 2023 |
| K & M Fencing Holdings Limited | Financial services | 2013 |
| K & M Fencing Limited | Construction | 2013 |
| K Balks Productions Ltd | Professional & scientific | 2024 |
| K&B World Ltd | Information & communication | 2013 |
| K4 Global Investments Ltd | Real estate | 2017 |
| Kalahari Keepsakes Ltd | Wholesale & retail | 2024 |
| Kalladi Capital Ltd. | Professional & scientific | 2016 |
| Kalm Rentals Limited | Real estate | 2024 |
| Kalman Hodosi Ltd | Health & social care | 2023 |
| Kaluca Consulting Limited | Information & communication | 2009 |
| Kama Capital Ltd | Real estate | 2014 |
| Kanban Live Ltd | Information & communication | 2012 |
| Kangaroo Coaching Ltd | Administrative & support | 2016 |
| Karen Froude Consulting Limited | Professional & scientific | 2021 |
| Karianca Limited | Agriculture & fishing | 1974 |
| Karini Ltd | Health & social care | 2025 |
| Karis Group Holdings Limited | Financial services | 2017 |
| Karis Group Limited | Professional & scientific | 2000 |
| Karis Winchester Limited | Real estate | 2005 |
| Karma Future International Limited | Wholesale & retail | 2018 |
| KAT Priest Consulting Limited | Professional & scientific | 2026 |
| Kate Jackson Limited | Professional & scientific | 2013 |
| Katherine Earnshaw Consulting Limited Limited | Professional & scientific | 2024 |
| Katherine Innes Consulting Limited | Construction | 2023 |
| Kathryn Hodnett Limited | Administrative & support | 2003 |
| Katy and RO Limited | Wholesale & retail | 2020 |
| Kavi Coffee Cafe Limited | Hospitality | 2024 |
| Kavi Coffee London Limited | Hospitality | 2026 |
| Kavi Coffee Management Limited | Hospitality | 2022 |
| Kavi Group Holdings Limited | Hospitality | 2026 |
| Kavod Group Ltd | Administrative & support | 2021 |
| KAY Mortgage Options Ltd | Financial services | 2024 |
| Kayjay Lettings Limited | Real estate | 2025 |
| KBM Construction Group Ltd | Construction | 2026 |
| KC (Winchester) Ltd | Households | 2009 |
| KC Counselling Ltd | Health & social care | 2020 |
| KC Eventing Ltd | Agriculture & fishing | 2013 |
| KC Public House Limited | Hospitality | 2025 |
| KCA Accounting Services Ltd | Professional & scientific | 2016 |
| KCT Profits Ltd | Real estate | 2024 |
| Kebab 88 Ltd | Hospitality | 2026 |
| Kechal | Professional & scientific | 2015 |
| Keddls Hosting Ltd | Administrative & support | 2021 |
| KEE Creative Limited | Professional & scientific | 2007 |