| Jesmond Tree Surgeons Limited | Administrative & support | 2015 |
| JGW Dodds Ltd | Agriculture & fishing | 2025 |
| JH Renewables Ltd | Energy | 2019 |
| Jigsaw Therapy Services Ltd | Health & social care | 2011 |
| JJV Group Ltd | Manufacturing | 2017 |
| JLK Plumbing and Heating Ltd | Construction | 2025 |
| JM Ridley & Sons Limited | Agriculture & fishing | 2017 |
| JMR (Farming) Limited | Financial services | 2017 |
| JND Associates Ltd | Health & social care | 2025 |
| JND Residences Ltd | Real estate | 2026 |
| Joehorse Power Ltd | Professional & scientific | 2018 |
| John Gregg & Sons Sports (Hexham) Limited | Wholesale & retail | 1978 |
| Jolso Limited | Other services | 2000 |
| Journey Enterprises Ltd | Health & social care | 1983 |
| JPP Agri Limited | Agriculture & fishing | 2025 |
| Jppd Group Limited | Professional & scientific | 2015 |
| JQC Consultants Limited | Professional & scientific | 2013 |
| JR Hotel and Restaurants Ltd | Hospitality | 2020 |
| Julia Alexander Ltd | Hospitality | 2025 |
| Juliet Rogers Limited | Other services | 2008 |
| Juniper Forestry and Environmental Services Ltd | Agriculture & fishing | 2019 |
| JW Carpets Limited | Wholesale & retail | 2022 |
| K Bell Accountancy Ltd | Professional & scientific | 2012 |
| K Smith Farming Limited | Administrative & support | 2009 |
| K&W Robson Property Ltd | Households | 2025 |
| Kaio Consulting Ltd | Professional & scientific | 2026 |
| KAM Courier Service Ltd | Transport & logistics | 2026 |
| KBH Developments NE Limited | Construction | 2024 |
| KBH Properties Limited | Real estate | 2016 |
| Kelvanis Ltd | Information & communication | 2026 |
| Kiani Healthcare Ltd | Health & social care | 2019 |
| Kielder Limited | Hospitality | 2001 |
| Kielder Observatory Services Limited | Wholesale & retail | 2014 |
| Kielder Valley Services Limited | Wholesale & retail | 2010 |
| Kitchen CX Limited | Professional & scientific | 2020 |
| Kitty Canavan Properties Ltd | Real estate | 2017 |
| Klism Ltd | Information & communication | 2014 |
| KMT Building Solutions Limited | Construction | 2017 |
| Knowles Brothers Limited | Real estate | 2006 |
| Kreative Allsorts Ltd | Arts & recreation | 2024 |
| KSM Associates Independent Financial Advisers Ltd | Financial services | 1991 |
| Kubu Technical Corrosion Consulting Limited | Professional & scientific | 2024 |
| L&S Advertising Limited | Professional & scientific | 2006 |
| L.Laing Property Holdings Ltd | Real estate | 2021 |
| L.P. Plant Hire & Groundworks Limited | Agriculture & fishing | 2018 |
| LA Rental Properties Ltd | Real estate | 2026 |
| Laba & Davy Limited | Hospitality | 2012 |
| Laing Protection Ltd | Wholesale & retail | 2020 |
| Land of Joy | Other services | 2010 |
| Landmark Consultancy Limited | Information & communication | 1998 |
| Landmark Golf Limited | Arts & recreation | 2015 |
| Lanefoot Holdings Limited | Financial services | 2019 |
| Langley DAM Glamping Ltd | Hospitality | 2017 |
| Langley Furniture Works Limited | Manufacturing | 2023 |
| Language Matters North East Ltd | Health & social care | 2024 |
| Launder and Press Hexham Ltd | Other services | 2025 |
| Lawnsward Limited | Real estate | 1987 |
| Learning With Lisa Ltd | Education | 2026 |
| Leazes Clinical Psychology Ltd | Health & social care | 2024 |
| Leazes Management Company Limited | Hospitality | 1983 |
| Leazes Management Services Limited | Professional & scientific | 2016 |
| Legally Blonde Solutions Ltd | Professional & scientific | 2019 |
| Let's GET Growing Limited | Health & social care | 2010 |
| Lewis Audio Limited | Professional & scientific | 2012 |
| LI Power Guide Ltd | Professional & scientific | 2013 |
| Life Cover for ALL Limited Liability Partnership | | 2010 |
| Life Song Ltd | Health & social care | 2013 |
| Lifeplan Financial Management Limited | Financial services | 2010 |
| Lighthouse Leisure (NE) Ltd | Extraterritorial | 2023 |
| Lightwater Solutions Ltd | Information & communication | 2026 |
| Lightyears (N.E ) Limited | Hospitality | 2018 |
| Lilly PAD MCT Limited | Manufacturing | 2010 |
| Limelight ME Limited | Administrative & support | 2023 |
| Link Imperium Limited | Information & communication | 2021 |
| Links Housing,Advice and Support for Young People | Other services | 1998 |
| Lion House Allendale Ltd | Hospitality | 2025 |
| Little Badgers Child Care Ltd | Health & social care | 2023 |
| Livaro Properties Limited | Real estate | 2025 |
| Living Space Properties Limited | Real estate | 2013 |
| Living Woods North East Community Interest Company | Education | 2017 |
| LJC Trading (North East) Ltd | Manufacturing | 2026 |
| Logic Manufacturing Limited | Manufacturing | 1986 |
| Logic MH Ltd | Wholesale & retail | 1991 |
| Lollamac Limited | Manufacturing | 2024 |
| Lowshield Ltd | Financial services | 2026 |
| LPG Vaporizers Ltd | Wholesale & retail | 2025 |
| LTS Commercial Limited | Construction | 2018 |
| LTS Refurb Property Maintenance Ltd | Construction | 2012 |
| LTS Refurbishment Limited | Construction | 1997 |
| LTS Resource Procurement Limited | Construction | 2012 |
| Ludman Planning Limited | Professional & scientific | 2018 |
| Ludman Spine Assist Limited | Professional & scientific | 2025 |
| Luke Jones Renewables Ltd | Construction | 2024 |
| Lukes Renewables Ltd | Professional & scientific | 2026 |
| Lunch in Bellingham Ltd | Hospitality | 2024 |
| LX Enterprises Ltd | Mining & quarrying | 2012 |
| M Design UK Ltd | Professional & scientific | 2009 |
| M R Cook Construction Limited | Construction | 1999 |
| M R Robson Electricity Services Ltd | Construction | 2006 |
| M R Robson Holdings Ltd | Financial services | 2021 |