| Labvac Ltd | Manufacturing | 2024 |
| Lacaz Bhurrut Ltd | Health & social care | 2021 |
| Lady UX Limited | Information & communication | 2018 |
| LAE Barbers Ltd | Other services | 2025 |
| Laine Health Limited | Health & social care | 2025 |
| Lajk Limited | Information & communication | 2022 |
| Lake Dene Escapes Limited | Health & social care | 2019 |
| Lamabuild Limited | Construction | 2010 |
| Land Science Limited | Professional & scientific | 2009 |
| Landucci-Harmey & Co Ltd | Professional & scientific | 2024 |
| Larboard Ltd | Information & communication | 2022 |
| Lareu & Gonzalez Ltd. | Information & communication | 2018 |
| Lark Precision Limited | Real estate | 1978 |
| Larkbetter Limited | Households | 1987 |
| Lastade Esports Ltd | Arts & recreation | 2025 |
| Lawnmower Services UK Ltd | Wholesale & retail | 2002 |
| Lawscheme Limited | Wholesale & retail | 1994 |
| Layover Financial Ltd | Information & communication | 2026 |
| LBS Britannia Limited | Real estate | 2026 |
| LEA Chic Ltd | Wholesale & retail | 2025 |
| Ledgerwise Ltd | Professional & scientific | 2025 |
| Legacy DRY Lining Ltd | Construction | 2019 |
| Legado Recruitment Ltd | Administrative & support | 2023 |
| Lets Holiday Ltd | Hospitality | 2026 |
| Leveret Consultancy & Training Ltd | Professional & scientific | 2025 |
| Lewvac Components Limited | Wholesale & retail | 2012 |
| Leylands Mill Ltd | Hospitality | 2025 |
| LGS Plumbing and Heating Ltd | Construction | 2009 |
| Lickee Limited | Wholesale & retail | 2023 |
| Life Centric Deliveries Ltd | Wholesale & retail | 2019 |
| Life Ledger Limited | Other services | 2017 |
| Lifte Holdings Limited | Financial services | 2025 |
| Lifte Limited | Administrative & support | 1991 |
| Lighting With Intent Limited | Construction | 1996 |
| Lilac Limited | Financial services | 2004 |
| Lincolnshire Shoulder and Elbow Ltd | Professional & scientific | 2018 |
| Linden Design (Sussex) Ltd | Construction | 2015 |
| Lindfield Enterprise Park Limited | Households | 1983 |
| Lindfield Plumbing & Heating Ltd | Construction | 2007 |
| Link Piece Limited | Professional & scientific | 2021 |
| Linkspan Holdings Limited | Financial services | 2015 |
| Lisand Property Developments Ltd. | Construction | 2013 |
| Lissaj Ltd | Administrative & support | 2013 |
| Listen to Engage Limited | Professional & scientific | 2020 |
| Little Orchards Childcare Ltd | Health & social care | 2025 |
| Little Pickles Pet Services Ltd | Other services | 2021 |
| Littlefields Close Management Company Limited | Households | 2016 |
| Lizshay Limited | Professional & scientific | 2009 |
| LJ Eighty Limited | Information & communication | 2015 |
| LJF Properties Ltd | Hospitality | 2011 |
| Lobule Ltd | Health & social care | 2016 |
| Locations Photography Limited | Professional & scientific | 1999 |
| Loch Aviation Services Limited | Transport & logistics | 2018 |
| Locks Farm Limited | Agriculture & fishing | 2013 |
| Locksmith 247 Ltd | Other services | 2021 |
| Lockstrood Consulting Ltd | Professional & scientific | 2015 |
| LOH Salons Limited | Other services | 2022 |
| London Estate Agents Limited | Administrative & support | 1999 |
| London RD Kebab Ltd | Hospitality | 2026 |
| Long Feng Foods Limited | Wholesale & retail | 2009 |
| Lost Dog Recovery UK South CIC | Agriculture & fishing | 2019 |
| Lovelinkldn Ltd | Wholesale & retail | 2024 |
| Loxwood Group Limited | Professional & scientific | 2024 |
| LTP Electrical Services Limited | Construction | 2014 |
| Lucastes Court Management Company Limited | Households | 2005 |
| Luckhurst Ventures Ltd | Real estate | 2024 |
| Lumafix Limited | Wholesale & retail | 1996 |
| Lumigo Travel & Events Limited | Administrative & support | 2025 |
| Lumiradx UK Ltd | Manufacturing | 2014 |
| Luxury Landscaping SW Ltd | Administrative & support | 2025 |
| Lynolyn Limited | Financial services | 2017 |
| M H Building Contractors Limited | Construction | 2012 |
| M J Whittaker Ltd | Construction | 2013 |
| M K Szymanski Ltd | Construction | 2022 |
| M P Screeding & Sons Limited | Construction | 2017 |
| M P Slight Limited | Construction | 2002 |
| M&E Hodges Ltd | Real estate | 2019 |
| M.M Sussex Enterprise Ltd | Wholesale & retail | 2016 |
| M.V.P.M Limited | Construction | 2011 |
| Macdonald Electrical Engineers Limited | Construction | 2002 |
| Magpie Accountancy Limited | Professional & scientific | 2018 |
| Magpie Limited | Wholesale & retail | 2009 |
| Mail International Limited | Administrative & support | 1985 |
| Mailpoint International Data Ltd | Professional & scientific | 1987 |
| Maindale Limited | Manufacturing | 2001 |
| Maitree Consultancy Ltd | Professional & scientific | 2022 |
| Makauri Limited | Administrative & support | 2010 |
| Makesure Insurance Services Limited | Financial services | 2004 |
| Malcolm Snowling Consulting Limited | Professional & scientific | 2019 |
| Maltow Ltd | Information & communication | 2022 |
| Mama Bars Limited | Hospitality | 2016 |
| Mama Event Foods Limited | Hospitality | 2025 |
| Mama Events Limited | Hospitality | 2025 |
| Mama Group Holding Ltd | Financial services | 2025 |
| Mama Pubs Greyhound Limited | Hospitality | 2026 |
| Mama Pubs Potters Arms Limited | Hospitality | 2024 |
| Mama Street Foods Limited | Hospitality | 2025 |
| Manifestation Global Ltd | Administrative & support | 2019 |
| Manne Ltd | Professional & scientific | 2011 |
| Manor Estate(Storrington)Management Company Limited | Households | 1965 |