| Landwood Properties Limited | Real estate | 2005 |
| Lawmill Construction Ltd | Construction | 2024 |
| Lawmill Properties Group Limited | Real estate | 2025 |
| Layfield Wealth Management Ltd | Financial services | 2017 |
| Leading Light Coaching Ltd | Professional & scientific | 2020 |
| LEF Property Services Ltd | Hospitality | 2019 |
| LEP Solutions Ltd | Information & communication | 2015 |
| Lesents Limited | Information & communication | 2022 |
| Let's GET Racing Limited | Agriculture & fishing | 2016 |
| Lets GET Healthy - Glphealth Ltd | Wholesale & retail | 2026 |
| Lets GET Healthy Limited | Health & social care | 2006 |
| Leven GAS and Property Developments Ltd | Construction | 2026 |
| Leven Generator Services Ltd | Manufacturing | 2025 |
| Leven Grove Management Limited | Households | 2022 |
| Leven Leisure Limited | Extraterritorial | 1999 |
| Levendale Consultants Limited | Construction | 2015 |
| Levenwood Ltd | Professional & scientific | 2010 |
| Levington Developments Ltd | Real estate | 2010 |
| Levington Energy Limited | Energy | 2017 |
| Levington Resources Limited | Water & waste | 2017 |
| Lewis Garbutt Golf Ltd | Education | 2022 |
| Lick Vintage Ltd | Wholesale & retail | 2025 |
| Lifetime Ceremonies UK Ltd | Other services | 2015 |
| Lissaman Logistics Ltd | Transport & logistics | 2024 |
| Lithothermal Resources Ltd | Mining & quarrying | 2023 |
| Littlewoods Heating & Plumbing Ltd | Construction | 2025 |
| LJO Business Services Ltd | Information & communication | 2015 |
| Lkandpartners Ltd | Professional & scientific | 2024 |
| LNG Developments Ltd | Construction | 2023 |
| Lordstone Financial Planning Limited | Financial services | 2019 |
| LOS Narejos Lettings Limited | Real estate | 2025 |
| Love More Lifestyle Limited | Wholesale & retail | 2024 |
| Love to Walk Ltd | Information & communication | 2016 |
| Lowes Electrical Limited | Construction | 2025 |
| LRL Engineering Services Ltd | Professional & scientific | 2025 |
| LTW Engineering Ltd | Professional & scientific | 2013 |
| Lucent Ltd | Information & communication | 2025 |
| Lucys Life and Reviews Ltd | Information & communication | 2025 |
| Lullstone Limited | Construction | 2024 |
| Luma Property Holdings Limited | Real estate | 2025 |
| Luxury Procurement Solutions Limited | Extraterritorial | 2018 |
| Lynain Ltd | Wholesale & retail | 2025 |
| M Cars (Teesside) Ltd | Wholesale & retail | 2018 |
| M G Y Consulting Limited | Professional & scientific | 2024 |
| M Shaw Training and Risk Assesment Services Ltd | Financial services | 2018 |
| Maceys (Yarm) Ltd | Hospitality | 2020 |
| Madvertising.Xyz Limited | Manufacturing | 2025 |
| Maher Entertainments Limited | Real estate | 1982 |
| Making Photographs Limited | Other services | 2014 |
| Manor Safety Limited | Professional & scientific | 2026 |
| Maplesden Engineering Ltd | Construction | 2023 |
| Marbec Limited | Administrative & support | 2017 |
| Maria Popescu Limited | Health & social care | 2013 |
| Marine Contractors (Newcastle) Limited | Wholesale & retail | 1990 |
| Mark Ridsdale Quantity Surveying Services Ltd | Professional & scientific | 2025 |
| Martin Rodgers T/A the Mockingbird Deli Ltd | Wholesale & retail | 2014 |
| Matthew Burr Limited | Hospitality | 2015 |
| Mayfair Products UK Ltd | Wholesale & retail | 2025 |
| Mcalog Holdings Limited | Extraterritorial | 2004 |
| Mccoy Engineering Ltd | Construction | 2018 |
| MD Properties (Teesside) Ltd | Real estate | 2020 |
| MDH OPS Ltd. | Professional & scientific | 2021 |
| Meadowhead Flowers Ltd | Wholesale & retail | 2015 |
| Medical Weight Care Ltd | Health & social care | 2022 |
| Medical Wellness Ltd | Health & social care | 2023 |
| Medida Software Ltd | Information & communication | 2009 |
| Medneuro Company Limited | Health & social care | 2015 |
| Mercurial Electrical Ltd | Construction | 2022 |
| Merlin Architectural Design Limited | Professional & scientific | 1998 |
| Merritts Solicitors LLP | | 2021 |
| Merryweather Court Management Company Limited | Real estate | 1995 |
| MES Engineering Services Limited | Professional & scientific | 2010 |
| MH Construction Project Management Services Limited | Construction | 2024 |
| MIB Safety Services Limited | Public administration | 2013 |
| Micasa Living Ltd | Real estate | 2026 |
| Mill Street Management Company Limited(The) | Professional & scientific | 1984 |
| Miller and Howell Limited | Wholesale & retail | 2025 |
| Minerva Mews Management Company Limited | Hospitality | 1995 |
| Mini Customs Motorsport Ltd | Wholesale & retail | 2021 |
| Miniforge Ltd | Professional & scientific | 2026 |
| Mint MAX Ltd | Hospitality | 2019 |
| Mjss Engineering Limited | Professional & scientific | 2018 |
| MK Swales & Company Ltd | Professional & scientific | 2022 |
| Modulek Solutions Ltd | Wholesale & retail | 2025 |
| Monk Properties Ltd | Real estate | 2016 |
| MOO Igloo Ltd | Hospitality | 2014 |
| MOS Training Ltd | Education | 2019 |
| Mount Stewart Properties Limited | Real estate | 2012 |
| MR Fit UK Limited | Extraterritorial | 1997 |
| Mrrn Ltd | Health & social care | 2024 |
| MSL Ventures Ltd | Real estate | 2020 |
| Murphy and Sons Investments Limited | Financial services | 2023 |
| MWM Technical Services Ltd. | Professional & scientific | 2023 |
| Myhseq Limited | Administrative & support | 2016 |
| N E Holdings Ltd | Other services | 2025 |
| N. Wheatley Limited | Households | 2018 |
| Nationwide Fencing Ltd | Administrative & support | 2025 |
| Navjaldhar Limited | Health & social care | 2024 |
| Ndar Offshore Services Ltd | Construction | 2023 |
| Ndta Ltd | Education | 2025 |