| Knect IT Limited | Information & communication | 2017 |
| Konsultera Ltd | Professional & scientific | 2014 |
| Koral Retail Ltd | Wholesale & retail | 2026 |
| KR Kitchens & Joinery Ltd | Construction | 2025 |
| Kraft Projects Ltd | Professional & scientific | 2025 |
| KS Construction Solutions Limited | Education | 2019 |
| KSG Services UK Ltd | Professional & scientific | 2025 |
| Kupolati Consulting Ltd. | Professional & scientific | 2018 |
| Kwok LUY Hairdressing Ltd | Other services | 2026 |
| Kyle Ramshaw Limited | Professional & scientific | 2026 |
| L & a Reinforcements Ltd. | Construction | 2005 |
| L & S Offshore Installations Ltd | Professional & scientific | 2018 |
| L & S Plumbing (NE) Ltd | Construction | 2012 |
| L&Jt Limited | Administrative & support | 2019 |
| L'Avenir Limited | Professional & scientific | 2013 |
| L. Crisp Plumbing & GAS Solutions Ltd | Construction | 2017 |
| L.J. Welch (Plant Hire) Limited | | 1975 |
| La-Atut Limited | Manufacturing | 2024 |
| Ladrona Ltd | Manufacturing | 2026 |
| Lafinca Properties Limited | Real estate | 2019 |
| Lakewind Limited | Extraterritorial | 2011 |
| Laksa Limited | Agriculture & fishing | 1993 |
| Lance Fennell IT Consultancy Ltd | Information & communication | 2025 |
| Langly Estates Limited | Real estate | 2003 |
| Laser Ways Durham Ltd | Other services | 2020 |
| Later Life Training Limited | Health & social care | 2003 |
| Laura Anderson Hair Ltd | Other services | 2019 |
| Lavelle Bikes Limited | Wholesale & retail | 2016 |
| Lavelle Coffee Limited | Wholesale & retail | 2017 |
| Lawrence's Garden Shop & Nursery Limited | Agriculture & fishing | 1990 |
| Layton Construction Ltd | Construction | 2025 |
| Lbb@Home Ltd | Arts & recreation | 2020 |
| LC Autos (NE) Limited | Wholesale & retail | 2025 |
| LE Petite Pizza Ltd | Hospitality | 2025 |
| Leadware Ltd | Information & communication | 2014 |
| LEE Harker Ltd | Administrative & support | 2016 |
| Leiper Windpower Limited | Energy | 2014 |
| Lemmer Development Solutions Limited | Administrative & support | 2012 |
| Lemon Bush Consulting Ltd | Information & communication | 2013 |
| Leniston Insurance Brokers Limited | Financial services | 2014 |
| Lenny's Entertainment Ltd | Hospitality | 2026 |
| Lenston Ltd | Energy | 2026 |
| Lenzi Ltd | Wholesale & retail | 2025 |
| LEO Rigging Services Limited | Construction | 2021 |
| Letang Ltd | Hospitality | 2025 |
| Letpropco Ltd | Real estate | 2011 |
| Leys Farm Limited | Agriculture & fishing | 1968 |
| Libervita Limited | Wholesale & retail | 2024 |
| Lightfoot Partners Ltd | Professional & scientific | 2025 |
| Lillie Design Management Ltd | Professional & scientific | 2023 |
| Lilly PAD Homes Ltd | Real estate | 2020 |
| Lily Aesthetics Ltd | Other services | 2022 |
| Liongate CS Limited | Professional & scientific | 2020 |
| Lionheart Rentals Limited | Real estate | 2026 |
| Lionheart Safety Supplies Limited | Wholesale & retail | 2020 |
| Lisa Crichton - Jones Consultancy Limited | Professional & scientific | 2024 |
| Lithiumionsafety Ltd | Professional & scientific | 2021 |
| Little Bookworm Education Company Ltd | Education | 2020 |
| Little Miss MOP NE Ltd | Administrative & support | 2026 |
| Little Shore Lets Limited | Real estate | 2021 |
| Liveware Group Limited | Administrative & support | 2016 |
| Liveware Recruitment Limited | Administrative & support | 2007 |
| Living Room Properties Limited | Households | 2019 |
| LJB Tech Limited | Professional & scientific | 2024 |
| Ljmm Logistics Ltd | Transport & logistics | 2024 |
| Ljsk Ltd | Real estate | 2015 |
| LKR Property Services Ltd | Construction | 2025 |
| LMB (Newcastle) Electrical Engineering Ltd | Manufacturing | 2017 |
| Lmes (NE) Ltd | Construction | 2024 |
| Loansdean Wood Investments Limited | Real estate | 2021 |
| Locke Financial Partners Ltd | Professional & scientific | 2025 |
| Lola & FLO Ltd | Wholesale & retail | 2016 |
| London & Regional (Chiswick) Ltd | Real estate | 2017 |
| London & Regional (Cobham) Ltd | Construction | 2018 |
| London & Regional (Stoke) Ltd | Real estate | 2018 |
| London & Regional Capital Ltd | Wholesale & retail | 1999 |
| London & Regional Developments Limited | Administrative & support | 1996 |
| Longacre Buist Ltd | Health & social care | 2025 |
| Longhirst Ltd | Information & communication | 2019 |
| Longhirst Properties Limited | Real estate | 1998 |
| Longhirst Spirits Limited | Wholesale & retail | 2025 |
| Longhorsley Explorers Community Interest Company | Education | 2008 |
| LOS Gavinas Ltd | Hospitality | 2022 |
| Lost Compass Ltd | Manufacturing | 2024 |
| Lovely Day Silk Bouquets Ltd | Wholesale & retail | 2021 |
| LSW Neuro-Rehab Limited | Health & social care | 2015 |
| LT Locks Ltd | Other services | 2023 |
| Ludovici Ltd | Manufacturing | 2010 |
| Lunamia Ltd | Real estate | 2022 |
| Lunarla AI Limited | Professional & scientific | 2025 |
| Lundgren Tours Ltd. | Administrative & support | 2016 |
| Luxury Carts UK Limited | Wholesale & retail | 2023 |
| Luxury Hot TUB Holidays UK Limited | Hospitality | 2020 |
| Lwh-Essentials Ltd | Wholesale & retail | 2025 |
| Lyall Rentals Ltd | Real estate | 2023 |
| Lynefield Park Limited | Construction | 2021 |
| Lynemouth and Ellington Miners Welfare Scheme Social Club Limited | Hospitality | 1992 |
| Lynemouth Day Centre Ltd | Health & social care | 2004 |
| Lynemouth Food & Wine Ltd | Wholesale & retail | 2025 |
| Lynemouth Hand Car Wash Ltd | Administrative & support | 2024 |