| Keysborough Limited | Other services | 1990 |
| Keytouch Computing Limited | Information & communication | 1996 |
| Keyway Services Limited | Real estate | 1999 |
| Kiln Ceramics Limited | Construction | 2002 |
| Kinderhurst Limited | | 1983 |
| King of Chichester Limited | Real estate | 1975 |
| Kingswood Close Residents Association Limited | Households | 1990 |
| KOP Kats Limited | Other services | 2003 |
| Krause Automation Ltd | Manufacturing | 1977 |
| Kreon Ltd | Professional & scientific | 2003 |
| KS Golf Pro Golf Ltd | Arts & recreation | 2018 |
| L & W Contractors Limited | Construction | 2001 |
| L J Borg Services Ltd | Health & social care | 2017 |
| L&W Rail Limited | Professional & scientific | 2002 |
| L.E.I.D. Limited | Other services | 2006 |
| L.I Plastering Ltd | Construction | 2023 |
| Ladybird Properties Limited | Administrative & support | 2002 |
| Lamina Dielectrics Limited | Manufacturing | 1967 |
| Lancing College Enterprises Ltd. | Administrative & support | 1981 |
| Lancing College Limited | Education | 1999 |
| Lancing Freehold Company Limited(The) | Households | 1985 |
| Land & New Homes Ltd | Real estate | 2020 |
| Landmark Housing Limited | Real estate | 1999 |
| Langford Financial Services Ltd | Financial services | 2024 |
| Langridge Developments (Sussex) Limited | Real estate | 1986 |
| Lanscape Limited | | 1989 |
| Lapthorn.Com Limited | Administrative & support | 2007 |
| Lasata Properties Limited | Real estate | 2004 |
| Laughton & Co Ltd | Professional & scientific | 2015 |
| Laurence Murray Limited | Health & social care | 2006 |
| Lavant Equestrian LLP | | 2006 |
| Lawrence England Ltd | Professional & scientific | 2005 |
| Leader Group Limited | Information & communication | 1977 |
| Lectrepair Windings Limited | Manufacturing | 1978 |
| LEO Panipucci Architect Limited | Professional & scientific | 2003 |
| Leon Paul Aviation Services Limited | Professional & scientific | 2006 |
| LES Humphrey Associates Limited | Professional & scientific | 2003 |
| LGM Properties Limited | Construction | 2002 |
| LH Mobiles & Computers Ltd | Wholesale & retail | 2015 |
| Lidsey Caravan Park Limited | Hospitality | 1964 |
| Lidsey Farm Limited | Agriculture & fishing | 2006 |
| Lighthouse Car Centre Ltd | Wholesale & retail | 2005 |
| Lilac Corporate Holdings Limited | Financial services | 2026 |
| Lillywhite Racing Limited | Arts & recreation | 2002 |
| Limpio Limited | Administrative & support | 2024 |
| Lincoln Court (Hove) Limited | Households | 2004 |
| Lindsell Properties Limited | Real estate | 1998 |
| Lines & James Limited | Real estate | 2005 |
| Lion Manpower Services Limited | Transport & logistics | 2008 |
| Lipace Limited | | 1983 |
| Liquid Level Systems Limited | Manufacturing | 1984 |
| Liquid Publications Limited | Information & communication | 2002 |
| Liverpool Urological Research and Services Limited | Professional & scientific | 1993 |
| Llamrai Ltd | Information & communication | 2016 |
| LMM Designs Ltd | Information & communication | 2007 |
| Logic Design Systems Limited | Information & communication | 2003 |
| London Merchant Nominees Limited | Administrative & support | 2023 |
| Lorlin Electronics Limited | Manufacturing | 1996 |
| Lotus Chichester Limited | Hospitality | 2017 |
| Louis Mackay Design & Illustration Ltd | Information & communication | 2007 |
| LP Electronics Limited | Information & communication | 2006 |
| LSH Solutions Ltd | Transport & logistics | 2022 |
| Ludgate 32 Limited | Real estate | 2025 |
| Lulu Mcardle Ltd | Professional & scientific | 2024 |
| Lund Bros (Holdings) Ltd. | Professional & scientific | 1946 |
| M & J Design Services Limited | Professional & scientific | 2007 |
| M a Lodge Jewellers Limited | Wholesale & retail | 2002 |
| M a Sports Limited | Arts & recreation | 2007 |
| M Bourne Limited | Health & social care | 2002 |
| M Hughes Brickwork Contractors Ltd | Construction | 2007 |
| M J H Enterprises Limited | Professional & scientific | 1998 |
| M. Booth (Builders) Limited | Manufacturing | 1976 |
| M. Harding Roofing Services Limited | Construction | 2002 |
| M.G.Jenner & SON Limited | Construction | 2004 |
| M.T. Fabrications Limited | Manufacturing | 1990 |
| M4 Launderettes Limited | Administrative & support | 2003 |
| Madspark Design Ltd | Other services | 2020 |
| Maidment Coach Finishers Limited | Transport & logistics | 1985 |
| Mainland Services Limited | | 1994 |
| Major Homes Limited | Real estate | 2005 |
| Manor Fields Horsham Residents Company Limited | Households | 1998 |
| Manor Fields NO.2 Residents Company Limited | Households | 1986 |
| Manorbrooks Ltd | Construction | 2005 |
| Manorwood Residents Management Company Limited | Households | 2022 |
| Mansell Mctaggart Burgess Hill Ltd | Real estate | 2008 |
| Mansell Mctaggart Cuckfield Ltd | Real estate | 2007 |
| Mansell Mctaggart Properties Limited | Real estate | 2001 |
| Manufacturing and Personnel Services Limited | Professional & scientific | 1989 |
| Marchants Limited | Real estate | 2003 |
| Marcus Agar Communications Ltd | Information & communication | 2004 |
| Marcus Leuw Limited | Extraterritorial | 2000 |
| Maritime House Limited | Wholesale & retail | 1984 |
| Mark Harrison Limited | Information & communication | 2002 |
| Mark's Building Limited | Construction | 2024 |
| Marsh & Co Accountants Ltd | Professional & scientific | 1995 |
| Marsh Graphic Design Limited | Administrative & support | 2005 |
| Martin & Co. (Worthing) Limited | Professional & scientific | 1999 |
| Martin Huxford Studio Ltd | Manufacturing | 1998 |
| Martyn Quarterman (Agio Consulting) Limited | Professional & scientific | 2004 |
| Mary ANN Seafoods Limited | | 1989 |