| JEE Developments Limited | Construction | 2025 |
| Jewitts Drywall Ltd | Construction | 2017 |
| JGM Properties Limited | Real estate | 2003 |
| Jhlonlineservices Ltd | Wholesale & retail | 2023 |
| JKB Logistics Ltd | Other services | 2022 |
| JKG Health Ltd | Professional & scientific | 2022 |
| JKG Property Ltd | Real estate | 2017 |
| JKG Retail Ltd | Wholesale & retail | 2014 |
| JL Security & Communications Ltd | Construction | 2026 |
| JL Woodhouse Holdings Ltd | Financial services | 2024 |
| JLA Property Group Limited | Real estate | 2025 |
| JLH Property Services Ltd | Construction | 2022 |
| JMG Healthcare (Yorkshire) Limited | Health & social care | 2000 |
| Joan Building Services Ltd | Construction | 2018 |
| Johal Haulage Ltd | Transport & logistics | 2011 |
| John Burley's Limited | Wholesale & retail | 2003 |
| John Laurence Holdings Limited | Professional & scientific | 2008 |
| Johnson UK Property Limited | Real estate | 2015 |
| Joka Developments Limited | Extraterritorial | 2012 |
| JOL Business Solutions Ltd | Administrative & support | 2006 |
| Jolly Housing Initiative C.I.C. | Real estate | 2025 |
| Jolly Housing Ltd | Real estate | 2025 |
| JPF Management Limited | Real estate | 2024 |
| Jpsmiththai Limited | Hospitality | 2022 |
| JR Building Contractors Limited | Construction | 2013 |
| JRB Properties (Doncaster) Limited | Real estate | 2023 |
| Juds Stock Solutions Limited | Wholesale & retail | 2021 |
| K & L Networks Limited | Information & communication | 2023 |
| K & N Catering Ltd | Hospitality | 2025 |
| K C Motors (South Yorkshire) Limited | Wholesale & retail | 2020 |
| K&S Properties Yorkshire Limited | Real estate | 2021 |
| K-Lodge Care Home Limited | Health & social care | 2021 |
| K-Net Installations Ltd | Construction | 2018 |
| K.I.T. Electroheat Limited | Administrative & support | 1999 |
| K9 Prime Ltd | Wholesale & retail | 2018 |
| Kaan Coffee 1 Ltd | Hospitality | 2026 |
| Kace Design Limited | Manufacturing | 2026 |
| Kael Homes Limited | Real estate | 2026 |
| Kaits Construction Ltd | Construction | 2025 |
| Karmel Limited | Transport & logistics | 1999 |
| Katana Installations Ltd | Other services | 2021 |
| Kaumaka Limited | Information & communication | 2017 |
| Kavanagh Rope Access Limited | Administrative & support | 2015 |
| KB Waste Consultancy Ltd | Professional & scientific | 2025 |
| Kdoll Ltd | Wholesale & retail | 2025 |
| Kemmie's Ltd | Health & social care | 2022 |
| Kepple Limited | Construction | 2012 |
| Kestrel Events Management Limited | Professional & scientific | 2022 |
| Kettlewell Property Rentals Ltd | Real estate | 2020 |
| Kevin Sutcliffe Financial Services Limited | Financial services | 2011 |
| Keyworth Electrical Limited | Construction | 2012 |
| KL PUB Co Limited | Professional & scientific | 2022 |
| Kleenz With CC Ltd | Administrative & support | 2025 |
| KMD Yorkshire Limited | Wholesale & retail | 2014 |
| KMW Blade Grinding & Sharpening Ltd | Manufacturing | 2019 |
| KMW Electrical Engineering Limited | Construction | 2012 |
| KO Potatoes Limited | Hospitality | 2025 |
| KOC Strength & Fitness Ltd | Arts & recreation | 2023 |
| Kool Technologies Ltd | Wholesale & retail | 2026 |
| Krown Fresh Ltd | Administrative & support | 2026 |
| Krsm Limited | Real estate | 1999 |
| L & D Holiday Lets Ltd | Hospitality | 2023 |
| L & E Education Limited | Education | 2024 |
| L & R Property Limited | Real estate | 2026 |
| L E Commercial Developments Limited | Construction | 2014 |
| L&D Foods Yorkshire Limited | Wholesale & retail | 2024 |
| L&J Housing Limited | Real estate | 2019 |
| L&R Homes Yorkshire Limited | Construction | 2025 |
| Lad.Whittall Ltd | Information & communication | 2014 |
| LAH DI DA Ltd | Other services | 2019 |
| Lakeside (Yorkshire) LLP | | 2011 |
| Lamont Johnson Ltd | Other services | 2012 |
| Lampitt Rail Services Limited | Professional & scientific | 2021 |
| Lancall Yorkshire Limited | Professional & scientific | 2011 |
| Landcross Limited | Real estate | 1974 |
| Laptops Hubb Ltd | Wholesale & retail | 2026 |
| Large Glass Limited | Information & communication | 2023 |
| Lashwy Lettings Limited | Real estate | 2023 |
| Laura Jane Aesthetics Ltd | Health & social care | 2018 |
| LB Mortgages Ltd | Financial services | 2019 |
| LC Remediation Contracting Ltd | Water & waste | 2018 |
| LDE Trading Limited | Wholesale & retail | 2026 |
| LDM Plant & Tool Hire Ltd | Other services | 2022 |
| Leadpower Ltd | Information & communication | 2025 |
| Leesing Marrison LEE Limited | Professional & scientific | 2007 |
| Legends Barbers (High ST) Ltd | Other services | 2022 |
| Legends Barbers (Mexborough) Ltd | Other services | 2025 |
| Leisure Carpets Direct Ltd | Manufacturing | 2021 |
| Lemon Sherbet Marketing Limited | Professional & scientific | 2016 |
| Leyland Corporate Finance Limited | Financial services | 2016 |
| LG People, Culture & Impact Consulting Ltd | Professional & scientific | 2025 |
| Libra Weighing Machines Limited | Manufacturing | 1994 |
| Lifting Point Limited | Manufacturing | 2026 |
| Lilgenvic Ltd | Health & social care | 2026 |
| Lime City Limited | Wholesale & retail | 2024 |
| Lindsay Rail Limited | Construction | 2020 |
| Line 01 Limited | Information & communication | 2002 |
| Line One Sales Limited | Information & communication | 1999 |
| Linkline (Yorkshire) Limited | Construction | 2009 |
| Links and Kins Ltd | Health & social care | 2023 |