| Leisure Attractions Limited | Arts & recreation | 2002 |
| Leisure Services Agency Limited | Arts & recreation | 1933 |
| Lemf Homes Limited | Real estate | 2020 |
| Lemon Limited | Administrative & support | 2007 |
| Lemon Taste Ltd | Hospitality | 2024 |
| Leopard PEL Limited | Extraterritorial | 1997 |
| Lesley Bowell Associates Limited | Education | 2005 |
| Letch Chips Ltd | Hospitality | 2012 |
| Letchworth Dental Surgery Limited | Health & social care | 2016 |
| Letchworth Garden City Angling Association Limited | Agriculture & fishing | 2003 |
| Lets Manage Investments Limited | Real estate | 2016 |
| Level-G Limited | Extraterritorial | 2003 |
| Levelguard Limited | Real estate | 1999 |
| Leveraged Finance Limited | Financial services | 2004 |
| Lewis & Sons Services Ltd | Construction | 2021 |
| Lewis Racing Limited | Arts & recreation | 2003 |
| LEX Strategic Limited | Other services | 2006 |
| LEY Hill Solutions Ltd | Professional & scientific | 2000 |
| Lfds Limited | Administrative & support | 2004 |
| LGL Interiors Limited | Construction | 2007 |
| LHS Networks Limited | Professional & scientific | 1998 |
| Liberal Premises (St.Albans) Limited | Real estate | 1949 |
| Libra Asset Management Limited | Professional & scientific | 2001 |
| Life Force Energy Limited | Education | 2005 |
| Lifecycle Consultants Limited | Information & communication | 2006 |
| Lifelight Limited | Health & social care | 2003 |
| Light Industry Productions Limited | Extraterritorial | 2005 |
| Lighting and General Limited | Professional & scientific | 1985 |
| Lila Game Ltd | Health & social care | 2025 |
| Lime Metals Limited | Extraterritorial | 2007 |
| Limousine Services Limited | Administrative & support | 1997 |
| Lincoln Brown (Accountants) Ltd | Professional & scientific | 2000 |
| Lincoln Brown Accounting Services Ltd | Professional & scientific | 1992 |
| Linda Lusardi Limited | Arts & recreation | 2002 |
| Linden Court Freeholders Ltd | Households | 2007 |
| Lindsman Properties (1810) Ltd | Extraterritorial | 2012 |
| Lindsman Properties (1811) Ltd | Extraterritorial | 2012 |
| Lindsman Properties (1821) Limited | Extraterritorial | 2018 |
| Linkbrand Limited | Wholesale & retail | 2001 |
| Linkup UK Tyres Ltd | Wholesale & retail | 2023 |
| Linoakley (NO. 106) Limited | Manufacturing | 1928 |
| Lion Heating & Plumbing Ltd | Construction | 2019 |
| Lion Public House Limited | Hospitality | 2003 |
| Lionheart Armoury Ltd | Wholesale & retail | 2024 |
| Little Acorns (UK) Limited | Real estate | 2005 |
| Little Big Fish Films Limited | Information & communication | 2005 |
| Little Steps Limited | Education | 1999 |
| Livingstone Medical Ltd | Information & communication | 1993 |
| LIZ Ice's Ltd | Hospitality | 2024 |
| LJC Plumbing Limited | Construction | 2025 |
| LKK Properties Ltd | Real estate | 2019 |
| LKK Property Holdings Ltd | Real estate | 2021 |
| LKP Productions Ltd | Information & communication | 2021 |
| LL Fitters Ltd | Construction | 2021 |
| Lloyd Cooper Motor Cycles Limited | Wholesale & retail | 1996 |
| Lloyd Harris Accounting Services Limited | Professional & scientific | 2002 |
| LMA Corporation Limited | Professional & scientific | 2013 |
| Lock & Load Films Limited | Information & communication | 2015 |
| Lockhart Properties Limited | Real estate | 2005 |
| Locklane Limited | Wholesale & retail | 1982 |
| Locum Investments Limited | Real estate | 2002 |
| Logam Limited | Real estate | 2002 |
| London & Overseas Property Co Limited | Real estate | 2002 |
| London Colney Business Services LLP | | 2005 |
| London Haulage (Hire) Limited | Transport & logistics | 2018 |
| London Legal International Limited | Other services | 2006 |
| London Surveyors Limited | Extraterritorial | 2000 |
| London Treasury Services Limited | Financial services | 1996 |
| Longdean Limited | Construction | 2003 |
| Longhay Limited | Agriculture & fishing | 2003 |
| Looking Good Gardens Limited | Administrative & support | 2003 |
| Louise Palmer-Thompson Investments Ltd | Extraterritorial | 2007 |
| Love Feet Limited | Health & social care | 2006 |
| LOW Carbon Contractors Limited | Construction | 2025 |
| Lower END Garage Limited | Wholesale & retail | 1978 |
| LRG Financial Solutions Limited | Financial services | 2003 |
| LRG Group Limited | Administrative & support | 1989 |
| LSP Associates Limited | Real estate | 2001 |
| LTV Trading Ltd | Financial services | 2021 |
| Luckins Consultants Limited | Real estate | 1975 |
| Ludgate Property Development Limited | Construction | 2004 |
| Luna Pharma Limited | Health & social care | 2022 |
| Lupo Limited | Real estate | 2004 |
| Lush Restaurants Limited | Hospitality | 2005 |
| Luton Investco (2) Limited | Professional & scientific | 2001 |
| Luvata Welwyn Garden Ltd | Manufacturing | 1991 |
| Luxury Limos London Ltd | Transport & logistics | 2025 |
| Luxury Living Concierge Services Ltd | Administrative & support | 2017 |
| LV Marketing Limited | Wholesale & retail | 2020 |
| LYD Global Capital Ltd | Financial services | 2025 |
| LYD Ltd | Information & communication | 2025 |
| Lynne Bell Limited | Professional & scientific | 2006 |
| Lyons Building Company Limited | Construction | 1997 |
| Lysi Limited | Professional & scientific | 2003 |
| M & a Builders Limited | Construction | 1996 |
| M & H Pickering Limited | Administrative & support | 2006 |
| M & I Properties Limited | Construction | 2016 |
| M a Fitzgerald Limited | Real estate | 2005 |
| M Coyne Supplies Ltd | Construction | 2019 |
| M G W (Accountancy Services) Ltd | Professional & scientific | 2002 |