| Lawnbrook Care Home Limited | Health & social care | 2015 |
| Lawrence Webb Limited | Construction | 1984 |
| Lawrin Group Ltd | Real estate | 2025 |
| Lawson Technology Consultancy Ltd | Information & communication | 2021 |
| Lawtronic Holdings Limited | Financial services | 2007 |
| Lawtronic Limited | Manufacturing | 2004 |
| Lawyalty Ltd | Professional & scientific | 2021 |
| Laxfield Estates Limited | Real estate | 2022 |
| Laxmi Events Ltd | Transport & logistics | 2014 |
| Laxmi Jewels Ltd | Wholesale & retail | 2022 |
| Laxmi UK Properties Ltd | Households | 2020 |
| Layercakecorp Ltd | Information & communication | 2022 |
| Layeredhomes Ltd | Real estate | 2025 |
| Laylab Consulting Limited | Health & social care | 2022 |
| Layo Wash UK Ltd | Other services | 2024 |
| Laza Care Ltd | Health & social care | 2025 |
| Lazar Print Limited | Manufacturing | 1986 |
| Lazy Susan Decor Ltd | Wholesale & retail | 2025 |
| La’Kola Ltd | Wholesale & retail | 2018 |
| LB Travel Solutions Ltd | Administrative & support | 2025 |
| LBE Construction Limited | Construction | 2007 |
| Lbfit Ltd | Arts & recreation | 2020 |
| LBL 1 Construction Ltd | Construction | 2023 |
| LBR Online Ltd | Information & communication | 2024 |
| Lbrok Ltd | Construction | 2025 |
| LC Build Ltd | Construction | 2025 |
| LC Flooring Watford Ltd | Wholesale & retail | 2016 |
| LC Made Ltd | Professional & scientific | 2024 |
| LCA Carpentry & Building Services Ltd | Construction | 2018 |
| LCP Advisory Limited | Administrative & support | 2025 |
| LCS Fabrication and Welding Ltd | Manufacturing | 2021 |
| LCS Management Ltd | Construction | 2013 |
| LCS Therapy Ltd | Health & social care | 2018 |
| LD Property Consultant Limited | Real estate | 2023 |
| LD QS Consultants Ltd | Construction | 2019 |
| LDC Elite Ltd | Construction | 2023 |
| LDF GAS Solutions Ltd | Construction | 2026 |
| LDM Solutions Limited | Information & communication | 2005 |
| LDN Plumbing & Heating Limited | Construction | 2016 |
| LDN Plumbing and Heating Services Ltd | Construction | 2023 |
| Ldsmjb Ltd | Wholesale & retail | 2025 |
| LE Transport Limited | Transport & logistics | 2025 |
| Leadership Cubed Ltd | Professional & scientific | 2024 |
| Leadship Design & Consulting Limited | Construction | 2018 |
| Leaf RAY Consultancy Limited | Real estate | 2011 |
| LEAGUE7 Ltd | Manufacturing | 2026 |
| Lean Construction Ltd | Construction | 2025 |
| Lean IA Ltd | Professional & scientific | 2019 |
| Leanier Ltd | Information & communication | 2025 |
| Leap Consulting Group Ltd | Information & communication | 2015 |
| Leap Horse Group of Industries Ltd | Manufacturing | 2022 |
| Leaponcloud Ltd | Professional & scientific | 2019 |
| Learning Works for Business Limited | Education | 2008 |
| Learnnlaugh Ltd | Wholesale & retail | 2023 |
| Leather Trade Limited | Wholesale & retail | 2019 |
| Leavesden Court Hall RTM Company Limited | Real estate | 2012 |
| Leavesden Solutions Ltd | Information & communication | 2019 |
| Leavesden Supermarket Ltd | Wholesale & retail | 2011 |
| Leckborough Limited | Real estate | 1971 |
| Lecoco Ltd | Information & communication | 2021 |
| LED Lighthouse Limited | Wholesale & retail | 2018 |
| Ledbury Group Investments Limited | Real estate | 2017 |
| Ledbury Group Limited | Real estate | 2015 |
| Ledbury Paint & Paper Ltd | Construction | 2025 |
| Ledneb Ltd | Administrative & support | 2008 |
| LEE Accounting Services 2018 Limited | Professional & scientific | 2018 |
| LEE Brockwitz Roofing Limited | Construction | 2013 |
| LEE Financial Services Ltd | Financial services | 2026 |
| Lees Place 1 Ltd | Real estate | 2025 |
| Lees Place 2 Ltd | Real estate | 2025 |
| Lees Place 3 Ltd | Real estate | 2025 |
| Lees Place Freehold Ltd | Financial services | 2025 |
| Leetcode Limited | Information & communication | 2023 |
| Leeward Care Limited | Health & social care | 2014 |
| LEF Systems (UK) Limited | Manufacturing | 2010 |
| Lefke Associates Limited | Professional & scientific | 2023 |
| Leftera Ltd | Transport & logistics | 2016 |
| Legacy Cutting Room Ltd | Other services | 2025 |
| Legacy Motors Automotive Ltd | Wholesale & retail | 2026 |
| Legendary Estates Ltd | Real estate | 2026 |
| Legendary Moments Ltd | Financial services | 2018 |
| Legit Deals Ltd | Wholesale & retail | 2024 |
| Legumi Foods Limited | Manufacturing | 2025 |
| Lehrity Ltd | Information & communication | 2014 |
| Leiber Properties Limited | Construction | 2016 |
| Leith Care Ltd | Health & social care | 2018 |
| Lekoni Limited | Wholesale & retail | 2023 |
| Leksander Ltd | Administrative & support | 2016 |
| Lemco Enterprises Limited | Financial services | 2011 |
| Lemmon Tree Consulting Limited | Professional & scientific | 2012 |
| Lendip Properties Limited | Real estate | 2002 |
| Lensology Limited | Wholesale & retail | 2019 |
| Lenta 2 Limited | Real estate | 2015 |
| Lenta Business Centres Limited | Real estate | 1982 |
| Lenta Business Space Limited | Professional & scientific | 1992 |
| Lenta Management Limited | Real estate | 2023 |
| Lenta Properties Limited | Real estate | 1981 |
| Lenton Engineering (Watford) Limited | Manufacturing | 2000 |
| Lenton Properties Limited | Real estate | 1990 |
| LEO Cosmin Constructions Limited | Construction | 2021 |