| Lollipops Schoolwear Ltd | Wholesale & retail | 2023 |
| London Paleo Girl Limited | Wholesale & retail | 2015 |
| Long Newton Web Design Limited | Information & communication | 2024 |
| Longbeck Auto Holdings Ltd | Financial services | 2024 |
| Longeaton Catering Limited | Wholesale & retail | 2019 |
| Loom Casa Limited | Wholesale & retail | 2025 |
| Lords Monumentals Limited | Other services | 2001 |
| Lorsa Real Estate Limited | Real estate | 2023 |
| Lost Tapes Ltd | Wholesale & retail | 2019 |
| Loud Rumours Limited | Manufacturing | 2025 |
| Loving Hands Support Limited | Health & social care | 2025 |
| LOW Lane Developments Limited | Real estate | 2020 |
| Lowther Instrumentation Ltd. | Professional & scientific | 2018 |
| Loyalty Matrix Trading Ltd | Wholesale & retail | 2026 |
| LP Psychology Ltd | Other services | 2020 |
| LRP Tees Limited | Real estate | 2015 |
| Lrss Groundworks Ltd | Construction | 2023 |
| LTH Executive Search Limited | Administrative & support | 2025 |
| LTJ Kent Limited | Wholesale & retail | 2018 |
| Ltlpxl Ltd | Information & communication | 2020 |
| LTP (NO.1) Ltd | Construction | 2025 |
| LTP (South) Ltd | Construction | 2025 |
| LTP Ltd | Construction | 2025 |
| LTW Electrical Engineering Ltd | Construction | 2024 |
| LU Lu's Gift Company Ltd | Wholesale & retail | 2021 |
| Luacefashion Ltd | Wholesale & retail | 2026 |
| Lucid Technology Solutions Ltd | Information & communication | 2018 |
| Lucky Comps A&A Ltd | Other services | 2025 |
| Lucy's Coffee House Ltd | Hospitality | 2023 |
| Ludley Rigging and Lifting Ltd | Construction | 2023 |
| Luigis Lanehouse Ltd | Hospitality | 2026 |
| Luigis Pizzeria Thornaby Ltd | Hospitality | 2024 |
| Lulsgate 1966 Limited | Extraterritorial | 2013 |
| Luma Entertainment Limited | Arts & recreation | 2022 |
| Lumeniv Ltd | Health & social care | 2026 |
| Lumex Ltd | Construction | 2025 |
| Luna Innovation Ltd | Wholesale & retail | 2026 |
| Lunar Event & Security Services Ltd. | Administrative & support | 2017 |
| Lunar IW Ltd | Professional & scientific | 2025 |
| Lunaria Somerset Ltd | Administrative & support | 2013 |
| Lunn Ventures Group Limited | Construction | 2005 |
| Lusso Designs Limited | Wholesale & retail | 2010 |
| LUX Interiors (NE) Ltd | Wholesale & retail | 2020 |
| Luxe Hair and Beauty Group Limited | Other services | 2023 |
| Luxe Hospitality Recruitment Ltd | Administrative & support | 2025 |
| Luxepour Resin Ltd | Construction | 2025 |
| Luxhaven Investments Ltd | Real estate | 2025 |
| LVS Hire Ltd | Wholesale & retail | 2011 |
| LW Engineering Services (North East) Limited | Professional & scientific | 2018 |
| LWP Contract Services Ltd | Administrative & support | 2019 |
| Lynnwood Vehicle Services Ltd | Wholesale & retail | 2013 |
| M & a Total Limited | Construction | 2015 |
| M & E North East Ltd | Professional & scientific | 2021 |
| M & J CIS Ltd | Construction | 2017 |
| M & R Finance Ltd. | Financial services | 2006 |
| M & S Instrument Design Services Limited | Professional & scientific | 2007 |
| M and Co Hair Ltd | Other services | 2013 |
| M and J Pet Supplies Ltd | Wholesale & retail | 2016 |
| M B Property Maintenance (NE) Limited | Administrative & support | 2024 |
| M D Vehicle Services Ltd | Wholesale & retail | 2022 |
| M Dodd Ltd | Professional & scientific | 2009 |
| M Forrester Landscapes Limited | Administrative & support | 2009 |
| M Harrison Ltd | Construction | 2026 |
| M Hart Ltd | Information & communication | 2018 |
| M Johnson Properties Limited | Real estate | 2017 |
| M K DIN Invest Ltd | Real estate | 2026 |
| M S H Teesside Limited | Real estate | 2018 |
| M Sadler Ltd | Administrative & support | 2007 |
| M T Haulage Ltd | Transport & logistics | 2013 |
| M T J Structures Ltd | Professional & scientific | 2008 |
| M V Rope Access Limited | Mining & quarrying | 2020 |
| M&B Built Limited | Other services | 2025 |
| M&M Engineering and Lifting Services Ltd | Administrative & support | 2016 |
| M&Sh Properties Limited | Real estate | 2026 |
| M. D. W. Express Ltd | Transport & logistics | 2015 |
| M. Plews Commercial Vehicle Repairs Limited | Wholesale & retail | 2014 |
| M.A. Cleaning Group Ltd | Administrative & support | 2018 |
| M.G.H Pro Ltd | Manufacturing | 2025 |
| M.I. Supplies Holdings Limited | Financial services | 2025 |
| M.I. Supplies Limited | Manufacturing | 2005 |
| M49 Engineering Ltd | Construction | 2025 |
| M:C (Teesside) Commercial Services Limited | Wholesale & retail | 2025 |
| M@R Haulage Limited | Transport & logistics | 2017 |
| MA Construction Teesside Ltd | Construction | 2024 |
| MA Horizon Limited | Wholesale & retail | 2025 |
| MA Signalling Services Limited | Administrative & support | 2011 |
| Maas Fast Foods Limited | Hospitality | 2026 |
| Maay's Closet Ltd | Wholesale & retail | 2023 |
| MAB Electrics & Maintenance Limited | Construction | 2005 |
| MAC Scitech Limited | Professional & scientific | 2012 |
| Macca Investment Holdings Ltd | Financial services | 2022 |
| Macdonald Investments NE Limited | Real estate | 2026 |
| Mach Engineering Ltd | Professional & scientific | 2021 |
| Mack Software Solutions Limited | Information & communication | 2018 |
| Mackenzie Surveying Ltd | Real estate | 2020 |
| MAD Dog Estates Ltd | Real estate | 2024 |
| Madabode Ltd | Real estate | 2021 |
| Made for Mutts Ltd | Wholesale & retail | 2026 |
| Made to Custom Ltd | Wholesale & retail | 2022 |
| Madhusri Retail Limited | Wholesale & retail | 2025 |