| James Walker HPR Limited | Construction | 2020 |
| Jamie Lamb Consulting Ltd | Professional & scientific | 2025 |
| Jamm Space Ltd | Real estate | 2024 |
| Jarvis Global Enterprises Limited | Administrative & support | 2020 |
| Jarvis Nationwide Removals Ltd | Transport & logistics | 2025 |
| Jarvis Window Wizards Limited | Other services | 2025 |
| Jascreative Ltd | Arts & recreation | 2019 |
| Javlamm Ltd | Professional & scientific | 2022 |
| JCL Design Ltd | Professional & scientific | 2020 |
| JCN Events Limited | Administrative & support | 2018 |
| JCP Hospitality Limited | Hospitality | 2024 |
| JDB Holdings Limited | Health & social care | 2016 |
| Jeantec Ltd | Professional & scientific | 2009 |
| JEG Media Ltd | Information & communication | 2026 |
| Jenner Wealth Management Ltd | Professional & scientific | 2020 |
| Jennyruth Workshops Ltd | Education | 2002 |
| Jervaulx Singers Limited | Administrative & support | 2021 |
| Jess Kidd Limited | Arts & recreation | 2018 |
| JET Promotional Services Limited | Professional & scientific | 1983 |
| JH Fencing Contractor Limited | Construction | 2022 |
| Jigsaw Recycling (N.E.) Ltd | Water & waste | 2021 |
| Jika Properties Ltd | Real estate | 2021 |
| JJE31 Limited | Information & communication | 2024 |
| JLH Group Ltd | Financial services | 2024 |
| JLH Homes Limited | Real estate | 2017 |
| JLH Ward Ltd | Real estate | 2017 |
| JMA Farms Limited | Agriculture & fishing | 2021 |
| Joby Johnson Social Media Ltd | Professional & scientific | 2026 |
| Jor-Event Power Ltd | Administrative & support | 2026 |
| Jorvik Ghosts Ltd | Wholesale & retail | 2024 |
| JP Carpet Care Ltd | Other services | 2018 |
| Jsal Developments Limited | Construction | 2022 |
| Jsal Properties Ltd | Real estate | 2022 |
| JSD Plumbing and Heating Services Limited | Construction | 2024 |
| JSL Construction Ltd | Construction | 2022 |
| Julkat Limited | Administrative & support | 2022 |
| Juniper Company Collective Ltd | Wholesale & retail | 2025 |
| Juniper Grove (Ripon) Management Company Limited | Households | 2018 |
| Juptus Limited | Professional & scientific | 2012 |
| JW FX Derivatives Limited | Other services | 2021 |
| K a Anderson (Metal Recyclers) Limited | Water & waste | 2002 |
| K and a Launderette LP | | 2019 |
| K J & S M French Limited | Agriculture & fishing | 2015 |
| K L I K S Solutions Limited | Information & communication | 2019 |
| K Lockwood Limited | Construction | 2003 |
| K W Properties Limited | Real estate | 2015 |
| K.J.R. Management (Developments) Limited | Manufacturing | 2004 |
| Kaimera Infusions Limited | Manufacturing | 2025 |
| Kairos Utilities Limited | Manufacturing | 2019 |
| Karma Village Ltd | Wholesale & retail | 2025 |
| Kd&Sg Courier Ltd | Construction | 2024 |
| Kearsley Road Limited | Real estate | 2017 |
| KEE BIO Ltd | Professional & scientific | 2020 |
| Kemlin Ltd | Extraterritorial | 2023 |
| KEN Rodney Construction Ltd | Construction | 2011 |
| Kermina Ltd | Real estate | 2021 |
| Kestons Investments Limited | Extraterritorial | 2016 |
| Kettlesing Distilling Company Limited | Manufacturing | 2016 |
| Kettlesing Investments Limited | Financial services | 2024 |
| Kettlewell Commercials Limited | Wholesale & retail | 1987 |
| Kettlewell Motorhomes Limited | Administrative & support | 2020 |
| Kilgram Grange Farm Limited | Agriculture & fishing | 1997 |
| Kilkenny House Ltd | Financial services | 2022 |
| Kineholme Garage Limited | Wholesale & retail | 1956 |
| Kirkby House Consultancy Services Ltd | Professional & scientific | 2017 |
| Kirkby Malzeard Business Services Ltd | Professional & scientific | 2018 |
| Kirkby Motors Garage Ltd | Wholesale & retail | 2023 |
| Kitchbuild Ltd | Construction | 2021 |
| Kitchen Warehouse UK Ltd | Wholesale & retail | 2007 |
| Knaresborough Movers Ltd | Transport & logistics | 2018 |
| Knaresfair Properties Ltd | Real estate | 2025 |
| Knott Automation Projects Ltd | Professional & scientific | 2011 |
| Knox Holdings Limited | Real estate | 2008 |
| Knox Pharmaceuticals Limited | Wholesale & retail | 1995 |
| Krbtmw Ltd | Hospitality | 2024 |
| L S Jointing Contractors Ltd | Construction | 2020 |
| Laing Consultancy Ltd | Professional & scientific | 2019 |
| Lambton Clothing Company Limited | Manufacturing | 2008 |
| Lambton Clothing Company Partnership LLP | | 2012 |
| Lambton Protocol Limited | Administrative & support | 2026 |
| Langleyscott Group Ltd | Professional & scientific | 2019 |
| Lark Mews Management Company Limited | Households | 2021 |
| Larks Nest Ltd | Construction | 2020 |
| Lasperhey Photography Limited | Professional & scientific | 2025 |
| Latchayya Enterprise Ltd | Real estate | 2024 |
| Lateral Investments (Burtree) Limited | Real estate | 2017 |
| Lateral Investments (Spalding) Limited | Construction | 2015 |
| Laver Services Limited | Professional & scientific | 2023 |
| Lavertech Consulting Ltd | Information & communication | 2014 |
| Laverton Securities Ltd | Real estate | 1991 |
| Lawnwith Services Limited | Real estate | 2024 |
| Lawson Building Limited | Construction | 2018 |
| Lawson William Limited | Information & communication | 2023 |
| Layton Developments Ltd | Real estate | 2016 |
| Layton Hill Hotels Ltd | Hospitality | 2018 |
| Leada Bikes Ltd | Wholesale & retail | 2022 |
| Leada Engineering Limited | Professional & scientific | 2001 |
| Leada Group Ltd | Financial services | 2021 |
| Leada ICA Ltd | Construction | 2019 |
| Leada Motors Ltd | Wholesale & retail | 2019 |