| Link Architectural Limited | Construction | 2014 |
| Lion Main Security Ltd | Administrative & support | 2025 |
| Little and Large Investments Limited | Real estate | 2018 |
| LJ Day Rail Consultancy Ltd | Construction | 2023 |
| LJC Property Maintenance Ltd | Construction | 2022 |
| Ljday Consultancy Limited | Construction | 2016 |
| LJR 2016 Ltd | Professional & scientific | 2016 |
| LKS Herts Ltd | Hospitality | 2024 |
| LKS Holdings Limited | Financial services | 2026 |
| LL Interim Consulting and Executive Coaching Ltd | Professional & scientific | 2023 |
| Llucas Properties Ltd | Real estate | 2024 |
| LM Auto Associates Ltd | Public administration | 2026 |
| Lobo Consultancy Ltd. | Information & communication | 2014 |
| Local-Social CIC | Health & social care | 2016 |
| Locamats Commercials Ltd | Other services | 2025 |
| Locamats Ltd | Information & communication | 2016 |
| Lockwash Limited | Real estate | 2024 |
| Lodge Estates (GT. Amwell) Limited | Real estate | 2016 |
| London Imperial Chauffeurs Ltd | Transport & logistics | 2023 |
| Longmore Property Services Limited | Real estate | 2021 |
| Loop Automation Limited | Manufacturing | 2023 |
| Loughton Plumbing & Heating Limited | Extraterritorial | 2009 |
| Louise and Paul Ltd | Arts & recreation | 2026 |
| Love Wins Ltd. | Hospitality | 2017 |
| Lovell Design Services Ltd | Professional & scientific | 2026 |
| LOW Cost Cars London Ltd | Wholesale & retail | 2025 |
| Lowry and Stevens Ltd | Construction | 2025 |
| LR Living Group Ltd | Wholesale & retail | 2016 |
| LRC Group Roofing and Building Ltd | Construction | 2026 |
| Lrrd Lettings Limited | Real estate | 2026 |
| LS Groundworks and Construction Ltd | Construction | 2013 |
| Lsalmon Advisory Ltd | Financial services | 2021 |
| LSP Haulage Services Limited | Transport & logistics | 2019 |
| LTC GAS and Heating Ltd | Construction | 2020 |
| LTH Utilities Ltd | Energy | 2019 |
| Ltuk Ltd | Wholesale & retail | 2018 |
| Luca Alexander London Ltd | Real estate | 2021 |
| Lucas Properties Commercial Ltd | Construction | 2025 |
| Lucky Five Star (UK) Limited | Real estate | 2014 |
| Lucy Lawson Limited | Professional & scientific | 2012 |
| Lucy Sweeney Limited | Hospitality | 2013 |
| Luke Jennings Tree Surgery Ltd | Agriculture & fishing | 2018 |
| Lulu Coffee Roasters Ltd | Manufacturing | 2015 |
| Lumo Group Limited | Administrative & support | 2026 |
| Lunarr Engineering Ltd | Wholesale & retail | 2019 |
| Lusso Property Developments Ltd | Construction | 2024 |
| Luvessa Home Ltd | Manufacturing | 2026 |
| LUX Lofts Ltd | Construction | 2018 |
| Luxury Property Solutions Ltd | Administrative & support | 2021 |
| Luxus Homes Ltd | Construction | 2017 |
| LV Connections Ltd | Construction | 2017 |
| LV Electrical Ltd | Construction | 2020 |
| Lwov Limited | Administrative & support | 2014 |
| Lyceum Productions Limited | Arts & recreation | 2015 |
| Lyncroft Mansions Limited | Households | 1996 |
| M & D Developments Limited | Construction | 1981 |
| M E Godley Limited | Construction | 2003 |
| M Fraser-Andrews Limited | Information & communication | 2024 |
| M G Electrical (Herts) Ltd | Construction | 2025 |
| M J Cleverdon Limited | Transport & logistics | 2011 |
| M K Independent Ltd | Construction | 2010 |
| M L 46 Ltd | Real estate | 2013 |
| M Power Carpentry Ltd | Construction | 2025 |
| M V Plastics Limited | Manufacturing | 1999 |
| M&K Electrical Services Ltd | Manufacturing | 2018 |
| M&S Guru State Ltd | Other services | 2025 |
| M-Gard Ltd | Construction | 2017 |
| M-Y Books Limited | Information & communication | 2007 |
| M.X.Mihov Ltd | Construction | 2025 |
| MAC Property (London) Ltd | Real estate | 2021 |
| Macamalan Limited | Information & communication | 2021 |
| Macav Ltd | Professional & scientific | 2015 |
| Macdon Transport Ltd | Transport & logistics | 2018 |
| Macexperience Group Limited | Administrative & support | 2014 |
| Maia Leadership Ltd | Professional & scientific | 2020 |
| Maibob Ltd | Professional & scientific | 2015 |
| Mailsave Limited | Transport & logistics | 2000 |
| Main Investments Ltd | Transport & logistics | 2011 |
| Mainstream Internet Limited | Information & communication | 2021 |
| Maji Ltd | Wholesale & retail | 2025 |
| Makevale Group Limited | Professional & scientific | 2002 |
| Maleon Construction Project Safety Limited | Administrative & support | 2007 |
| Malthouse Mews Management Company Limited | Real estate | 2016 |
| Maltings Antiques Limited | Extraterritorial | 2018 |
| Maltings Trustees Limited | Financial services | 2017 |
| Maltons Restaurant Limited | Hospitality | 2019 |
| Mangiarsano Limited | Wholesale & retail | 2019 |
| Mango Projects Hertfordshire Limited | Construction | 2020 |
| Manners Investments Ltd | Real estate | 2025 |
| Manorvale Properties Limited | Households | 2005 |
| Maomao LIN Ltd | Wholesale & retail | 2021 |
| MAPLES6 Consultancy Ltd | Administrative & support | 2023 |
| Mappingmjt Ltd | Education | 2023 |
| Marcus & Byatt Property Services Limited | Real estate | 2021 |
| Maria Akore Photography Ltd | Professional & scientific | 2023 |
| Mark Nine Limited | Manufacturing | 1999 |
| Markclose Limited | Extraterritorial | 1989 |
| Marketing Outsource Limited | Professional & scientific | 2020 |
| Markmay Group Ltd | Administrative & support | 2024 |
| Markwell Peck (UK) Ltd | Construction | 2006 |