| J & P Group Holdings Ltd | Financial services | 2026 |
| J P Bulk Haulage Ltd | Transport & logistics | 2011 |
| J Reid Engineering Limited | Manufacturing | 2002 |
| J&M Pharmaceutical Ltd | Wholesale & retail | 2021 |
| J&M Trees & Gardening Ltd | Administrative & support | 2025 |
| J&P Group Northeast Ltd | Professional & scientific | 2024 |
| J&P Group Services Limited | Professional & scientific | 2008 |
| J&P Ventures LLP | | 2018 |
| J. Reid Trading Limited | Manufacturing | 1984 |
| J.F. Rogers & Sons Limited | Construction | 1987 |
| J.Palmer & Co.(Glaziers)Limited | | 1962 |
| J.R. Webster and Company Limited | Wholesale & retail | 1978 |
| J.T. Hewitt & SON Limited | Construction | 1998 |
| Jacksons Car Dismantlers Limited | Water & waste | 2003 |
| Jade Noodle & Dumpling House Ltd | Hospitality | 2026 |
| Jafar Car Sale Limited | Wholesale & retail | 2024 |
| Jamieson Developments Ltd | Construction | 2021 |
| Jamieson Estates Ltd | Real estate | 2024 |
| Jason Allin Flooring Limited | Construction | 2006 |
| JC Group Limited | Construction | 2022 |
| JC Medical Training Limited | Health & social care | 2015 |
| JDM Civils Ltd | Construction | 2024 |
| JG Mortgage Services Limited | Financial services | 2021 |
| JJT Master Ltd | Professional & scientific | 2019 |
| JM Holdings (NW) Ltd | Financial services | 2020 |
| JM Technical Services Limited | Other services | 2024 |
| JMS NDT Ltd | Professional & scientific | 2023 |
| Joana Services Ltd | Administrative & support | 2024 |
| John FOX Plant Limited | Construction | 1977 |
| Join the Dots Marketing Ltd | Professional & scientific | 2020 |
| Jones Burgess Services Ltd | Construction | 2025 |
| Jones City Stays Ltd | Real estate | 2024 |
| JPW Davies Services Limited | Professional & scientific | 2010 |
| JR Mortgage Solutions Ltd | Financial services | 2026 |
| JR Properties Group Ltd | Administrative & support | 2025 |
| JRR Contracting Limited | Construction | 2024 |
| JS Creations Ltd | Professional & scientific | 2025 |
| Jspt Health Studio Ltd | Arts & recreation | 2015 |
| Jubilee Garage (Deeside) Ltd | Wholesale & retail | 2012 |
| Juniper Fizz Ltd | Wholesale & retail | 2019 |
| Jupiter Retail Ltd | Wholesale & retail | 2023 |
| Just Automate IT Ltd | Information & communication | 2025 |
| JW Electrical Design Limited | Extraterritorial | 2021 |
| JWD Capital 2 Limited | Professional & scientific | 2017 |
| K & C Sutton Properties Limited | Real estate | 2009 |
| K Phillips Building & Maintenance Ltd | Construction | 2024 |
| K&M Corporation Ltd | Financial services | 2023 |
| K&M Estate Management Ltd | Real estate | 2023 |
| KA Design Consulting Ltd | Professional & scientific | 2025 |
| Kaata Enterprise Ltd | Wholesale & retail | 2024 |
| Kamakshi Ltd | Professional & scientific | 2015 |
| Kamski Engineering Limited | Other services | 2019 |
| Kavod Consultancy Security & Services Ltd | Professional & scientific | 2019 |
| Keating Specialist Cylinders Limited | Manufacturing | 2019 |
| Kemitron Manufacturing Limited | Manufacturing | 1990 |
| Kenmac Haulage Limited | Transport & logistics | 2019 |
| Keogh North West Ltd | Construction | 2020 |
| Kim's Sandwich Shop Limited | Hospitality | 2026 |
| Kingdom Inland Trading Limited | Extraterritorial | 1995 |
| Kingsbury Engineering Limited | Manufacturing | 2020 |
| Kirk P Limited | Wholesale & retail | 2019 |
| KMS New Build Limited | Construction | 2022 |
| Koselxpress Logistics Ltd | Transport & logistics | 2025 |
| Kozubek Ltd | Transport & logistics | 2019 |
| Kristian Palmer Fitness Ltd | Arts & recreation | 2025 |
| KUB Studios Ltd | Information & communication | 2009 |
| Kustro Limited | Wholesale & retail | 2015 |
| Kwik-Mot Ltd | Wholesale & retail | 2006 |
| Kymax Ltd | Real estate | 2023 |
| L JM Windows Ltd | Construction | 2026 |
| L.A. Davies Construction Ltd | Construction | 2011 |
| Lacey Goodfood Ltd | Hospitality | 2026 |
| Ladelfa Estates Limited | Real estate | 2023 |
| Ladelfa Properties Limited | Real estate | 2024 |
| Lamar Ceramics Limited | Wholesale & retail | 2023 |
| Lamb Inspection Ltd | Professional & scientific | 2024 |
| Lami Perfumes Ltd. | Wholesale & retail | 2024 |
| Lance Blades Limited | Professional & scientific | 1968 |
| Land Master 4X4 Limited | Administrative & support | 2015 |
| Landstruction Limited | Construction | 2010 |
| Lannis Limited | Professional & scientific | 2011 |
| Larafaye Ltd | Wholesale & retail | 2019 |
| Laura Anne Hospitality Consultant Ltd | Professional & scientific | 2020 |
| Laure Fraval Consulting Limited | Education | 2017 |
| Lavish Spaces Ltd | Construction | 2023 |
| LCA Controls Limited | Professional & scientific | 2017 |
| LCA Group Limited | Manufacturing | 1991 |
| LCA Holdings Limited | Manufacturing | 2017 |
| LCA Site Projects Limited | Construction | 2016 |
| Ldcretail Ltd | Wholesale & retail | 2023 |
| LDH Engineering Ltd | Professional & scientific | 2025 |
| Leading Edge Engineering Limited | Manufacturing | 2024 |
| Leba Systems Limited | Administrative & support | 2002 |
| Leeaccount Ltd | Professional & scientific | 2024 |
| LEM Building Surveying Ltd | Professional & scientific | 2022 |
| Lemons to Lemonade LLP | | 2018 |
| LES Roberts Light Haulage Limited | Transport & logistics | 2014 |
| Lewis Property (Ruthin) Limited | Real estate | 2003 |
| Life in the Past Lane Limited | Arts & recreation | 2025 |
| Lifestyle Nutrition and Health Ltd | Other services | 2022 |