| Jordan Milne Joinery Limited | Construction | 2022 |
| JR Whelan Holdings Ltd | Financial services | 2024 |
| JS Bajwa and Sons Ltd | Wholesale & retail | 2019 |
| Jssn Limited | Professional & scientific | 2025 |
| JT Inspection Ltd | Professional & scientific | 2023 |
| Jubilee Caravans Limited | Transport & logistics | 2016 |
| Julie's Support Services Ltd | Transport & logistics | 2025 |
| Just Meat Ashington Ltd | Wholesale & retail | 2025 |
| K J Brown Property Limited | Real estate | 2021 |
| K Plastics Limited | Wholesale & retail | 2010 |
| Kathie Wilcox Communications Ltd | Professional & scientific | 2021 |
| Katzsol Ltd | Real estate | 2023 |
| KC Forrest Auto Dismantler Limited | Other services | 2011 |
| KDF Retail Ltd | Wholesale & retail | 2023 |
| KDH Homes Limited | Real estate | 2013 |
| Keen Property Services Ltd | Real estate | 2020 |
| Kelco's Car Sales Ltd | Professional & scientific | 2014 |
| Kelcos MOT Ashington Ltd | Wholesale & retail | 2026 |
| KEN Routledge Limited | Information & communication | 1996 |
| Keren Locke Consulting Limited | Professional & scientific | 2014 |
| Kevin Stephens Consulting Limited | Professional & scientific | 2025 |
| Keywordloom Ltd | Professional & scientific | 2025 |
| Kingsmead (Wooler) Management Company Limited | Real estate | 2021 |
| Kirk Building and Carpentry Ltd | Construction | 2018 |
| Kismar Limited | Real estate | 2015 |
| KJJ Services Limited | Professional & scientific | 2025 |
| Koast Radio Limited | Information & communication | 2013 |
| Kudos Windows Limited | Manufacturing | 2006 |
| L & R Wall Ltd | Mining & quarrying | 2015 |
| L Dodds Bolting Services Ltd | Mining & quarrying | 2024 |
| L Hindson Ltd | Mining & quarrying | 2018 |
| L19 Limited | Other services | 2009 |
| LA Casa NE Ltd | Hospitality | 2020 |
| LA GAS Heating & Plumbing Ltd | Construction | 2021 |
| Ladhar Lodges Ltd | Hospitality | 2016 |
| Ladhar Stores Limited | Wholesale & retail | 2012 |
| Land Trade Ltd | Real estate | 2018 |
| Laputa Properties Ltd | Hospitality | 2021 |
| Lastborn Afro Caribean Food Store Ltd | Wholesale & retail | 2023 |
| Lawford Dunn & Co. Ltd. | Financial services | 2001 |
| Lawford Dunn Holdings Limited | Financial services | 2023 |
| Layer 7 Limited | Information & communication | 2010 |
| LB FO Limited | Professional & scientific | 2019 |
| Lemin Consulting Limited | Professional & scientific | 2014 |
| Lemon Property Ltd | Construction | 2012 |
| Lepo Ltd | Professional & scientific | 2019 |
| Lets Manage North East Limited | Real estate | 2011 |
| Letscore Limited | Real estate | 2011 |
| Lewis Consultancy Solutions Limited | Professional & scientific | 2022 |
| Lewis Wood Bros Ltd | Wholesale & retail | 2015 |
| LG Designer Maker CIC | Manufacturing | 2020 |
| LHS Removals Ltd | Transport & logistics | 2023 |
| Life Factory Ltd | Health & social care | 2023 |
| Lima Hand Carwash (NE) Ltd | Other services | 2024 |
| Linda Holdings Limited | Financial services | 2021 |
| Lindanna (Southtown Road) Limited | Construction | 2021 |
| Lindanna Holdings Limited | Financial services | 2019 |
| Lindanna Properties Limited | Real estate | 2015 |
| Lindanna Property Investments Limited | Real estate | 2015 |
| Lindanna Property Limited | Real estate | 2022 |
| Lindanna Property Services Limited | Construction | 2022 |
| Lindisfarne Timber Frame Ltd | Construction | 2003 |
| Lintonville 131 Ltd | Professional & scientific | 2017 |
| Lintron Electronics Limited | Manufacturing | 1988 |
| Little Acorns (Newbiggin) Limited | Health & social care | 2022 |
| Little Learners Franchise Limited | Education | 2015 |
| Llamedosus Limited | Real estate | 2016 |
| Lockdecoders Ltd | Manufacturing | 2011 |
| Logan Lewis Recruitment Ltd | Professional & scientific | 2016 |
| Lonsdale Energy Ltd | Mining & quarrying | 2018 |
| Lotus Fitness Studios Ltd | Arts & recreation | 2015 |
| Love and Gratitude Limited | Health & social care | 2011 |
| LRG Motorsport Ltd | Arts & recreation | 2022 |
| Lsln Property Ltd | Real estate | 2024 |
| LT88 Projects Ltd | Manufacturing | 2014 |
| Lucas Residentials Ltd | Real estate | 2021 |
| Lucky Panda Inc Ltd | Hospitality | 2024 |
| Ludlow Street Limited | Arts & recreation | 2021 |
| Lugor Ltd | Hospitality | 2026 |
| Luna Muse Ltd | Wholesale & retail | 2025 |
| LUX Decor Collection Ltd | Wholesale & retail | 2025 |
| Luxebazaar Ltd | Wholesale & retail | 2026 |
| Lynx Precast Limited | Manufacturing | 2013 |
| M & D Johnston Properties Ltd | Real estate | 2024 |
| M & K Jewellers Ltd | Wholesale & retail | 2010 |
| M H Trading (NE) Limited | Hospitality | 2018 |
| M J B Plant & Marine Services Limited | Wholesale & retail | 2018 |
| M O F Investments Limited | Real estate | 2021 |
| M Thompson Bolting Solutions Ltd | Energy | 2025 |
| M&L Properties NE Limited | Real estate | 2024 |
| M.K. Electrics Limited | Construction | 2007 |
| MA Real Investments Ltd | Real estate | 2022 |
| MAA Food Services Ltd | Hospitality | 2019 |
| Maac.Tech Engineering Limited | Energy | 2025 |
| Maddie Maughan Limited | Arts & recreation | 2017 |
| MAE Cabunoc Ltd | Health & social care | 2022 |
| Majestic Flooring North East Ltd | Construction | 2025 |
| Makaveli TM Limited | Construction | 2026 |
| Make NE CIC | Wholesale & retail | 2025 |
| Mandy Rail Limited | Administrative & support | 2016 |