| JTL Hire Ltd | Construction | 2014 |
| JTL MR DIG (Groundworks) Ltd | Construction | 2019 |
| JTL Scaffolding Ltd | Construction | 2014 |
| JTL Special Projects Ltd | Construction | 2017 |
| JTM Giftware Limited | Manufacturing | 2024 |
| Juliette Stephenson Ltd | Wholesale & retail | 2017 |
| Just Baked Desserts Ltd | Manufacturing | 2019 |
| Just Curtains Ltd | Manufacturing | 2024 |
| Just for Women Centre C.I.C. | Education | 2011 |
| JW Smith Motor Company Ltd | Wholesale & retail | 2025 |
| K & R Taxis Ltd | Transport & logistics | 2023 |
| K C B Furnishings Ltd | Wholesale & retail | 2019 |
| K I I D Construction Limited | Construction | 2005 |
| K Lumley Company Limited | Professional & scientific | 2024 |
| K Troy G P Services Ltd | Health & social care | 2020 |
| K&J Bygate Ltd | Hospitality | 2017 |
| Kaam Properties Limited | Real estate | 2022 |
| Kadal Kuthirai Ltd | Wholesale & retail | 2025 |
| KAI Ventures Limited | Transport & logistics | 2019 |
| KAM T1 Ltd | Hospitality | 2025 |
| KAM T2 Ltd | Hospitality | 2025 |
| Kapture Krew Limited | Information & communication | 2025 |
| Karen Blackburn Consulting Limited | Hospitality | 2005 |
| Kathryn Dorner Property Ltd | Real estate | 2010 |
| KB Success Limited | Real estate | 2020 |
| KBO Dynamics International Ltd | Administrative & support | 2010 |
| KC Bespoke Floors Ltd | Construction | 2025 |
| KC Renewable Solutions Limited | Construction | 2025 |
| KCB Beds Ltd | Wholesale & retail | 2025 |
| Keen 12 Limited | Wholesale & retail | 2012 |
| Keep Moving Community Interest Company | Arts & recreation | 2018 |
| Keep Tiling Limited | Construction | 2024 |
| Keith Lines Construction Limited | Construction | 2022 |
| Keith Lines Properties Limited | Real estate | 2024 |
| Kelly Paving & Groundworks Limited | Construction | 2016 |
| KEN Brown Agencies Limited | Wholesale & retail | 2010 |
| KEN Madge and SON Ltd | Construction | 2026 |
| KEN Thomas Site Clearance Limited | Water & waste | 2007 |
| Kenpartner Limited | Real estate | 2020 |
| Kerect Steel Limited | Administrative & support | 2014 |
| Kerr & Co Accountants Limited | Professional & scientific | 2015 |
| Kevin Snowdon Groundworks Limited | Construction | 2004 |
| Keylink Design International Ltd | Other services | 2019 |
| Khvm Limited | Real estate | 2025 |
| Kindle Green Properties Limited | Real estate | 2020 |
| Kingsman Construction NE Limited | Construction | 2017 |
| Kj.Electrics North East Ltd | Construction | 2022 |
| Kjbh Limited | Construction | 2025 |
| KL Keystone Limited | Real estate | 2025 |
| KLP Construction Limited | Construction | 2025 |
| KLR Medical Ltd | Health & social care | 2020 |
| KLW Investment Limited | Real estate | 2021 |
| KLW NE Ltd | Hospitality | 2024 |
| KMK Agents Limited | Administrative & support | 2020 |
| KMK Pallets Ltd | Manufacturing | 2008 |
| KNA Group Ltd | Real estate | 2023 |
| Knightsbridge Property Developments Limited | Construction | 2025 |
| Knitsley Grange Farm Shop Limited | Wholesale & retail | 2008 |
| Know Your Partner Limited | Information & communication | 2024 |
| Ko-Ach Professional Audio Visual Lighting & Networking Solutions Ltd | Wholesale & retail | 2006 |
| KP CAD Services Ltd | Professional & scientific | 2010 |
| KT Waste Management NE Ltd | Water & waste | 2026 |
| L & L Wanmarch Ltd | Hospitality | 2025 |
| L T Electrical Services North East Ltd | Construction | 2025 |
| L W M Rentals Limited | Administrative & support | 2009 |
| L&D Taxi's NE Ltd | Transport & logistics | 2023 |
| L&G Beck Property Limited | Transport & logistics | 2013 |
| L&N Limited | Transport & logistics | 2024 |
| L.A.P. Ltd | Real estate | 2025 |
| L.M Pro Clean & Maintenance Ltd | Administrative & support | 2022 |
| LAB96 Limited | Construction | 2023 |
| Land Barbers Ltd | Other services | 2025 |
| Langington Limited | Administrative & support | 2017 |
| Lanoli Holdings Limited | Financial services | 2021 |
| Lantech Ltd | Information & communication | 2022 |
| Later Life Wealth Management Limited | Professional & scientific | 2022 |
| Laundrew Ltd | Extraterritorial | 2023 |
| Layke Ltd | Construction | 2025 |
| Lazo (Newcastle) Ltd | Hospitality | 2024 |
| LB Eridanus Entertainment Limited | Professional & scientific | 2006 |
| LB Solutions NE Ltd | Professional & scientific | 2024 |
| LD First Class Fitness Limited | Other services | 2018 |
| LDS Drilling Limited | Construction | 2025 |
| LE Nail and Spa Ltd | Other services | 2024 |
| Lead Key Limited | Real estate | 2020 |
| Lease Hire UK Limited | Real estate | 2007 |
| Lee's Taxis Limited | Transport & logistics | 2026 |
| Leonard General Services Ltd | Construction | 2026 |
| LET Property Development Ltd | Real estate | 2024 |
| LF Joinery & Building Limited | Construction | 2024 |
| LGI Estates Limited | Real estate | 2023 |
| Life in Harmony Limited | Real estate | 2023 |
| Lihle Ltd | Health & social care | 2024 |
| Linskill Park Bistro Limited | Hospitality | 2018 |
| Little Paws Atelier Ltd | Wholesale & retail | 2026 |
| Lively Land Limited | Real estate | 2020 |
| LJM Cladding Ltd | Construction | 2025 |
| Lleks Group Limited | Wholesale & retail | 2021 |
| LM Joinery, Kitchens & Bathrooms Ltd | Construction | 2021 |
| LMH U.K. Limited | Real estate | 2020 |