| Horace Fuller Limited | Wholesale & retail | 1939 |
| Horsham Business Systems Limited | Other services | 1997 |
| Horsham Family Lawyers Ltd | Professional & scientific | 2015 |
| Horsham Graphics Limited | Professional & scientific | 2002 |
| Horsham Plastics Limited | Manufacturing | 1973 |
| Horsham Windows Limited | Construction | 2007 |
| Horsley Developments Limited | Professional & scientific | 2006 |
| Howitt Machine Tools Limited | Transport & logistics | 1973 |
| HPC Engineering Limited | Professional & scientific | 2006 |
| HPC Public Limited Company | Manufacturing | 1959 |
| Huggett Consulting Limited | Professional & scientific | 2009 |
| Hughes Partners LLP | | 2026 |
| Hurstpierpoint Property Development Limited | Construction | 2018 |
| Hydro Power UK Limited | Manufacturing | 1999 |
| I Feel Like a Million Dollars Limited | Health & social care | 2007 |
| I Munslow Consulting Ltd | Professional & scientific | 2019 |
| I T Productions Limited | Information & communication | 1996 |
| I.P.S. (Law Agents) Limited | | 1988 |
| IAN Foster Limited | Manufacturing | 2007 |
| IAN Young & Company (Aerosols) Limited | Professional & scientific | 1968 |
| Icon Consulting (UK) Ltd | Information & communication | 1998 |
| Idealmgtuition Ltd | Education | 2022 |
| Ideas 4 Adis Limited | Education | 2004 |
| Illumgaard Limited | Real estate | 1999 |
| Impact Foundation | Health & social care | 1985 |
| Imperial Private Practice Limited | Health & social care | 2014 |
| Imperial Private Ultrasound Limited | Health & social care | 2014 |
| Income Data Stream Limited | Professional & scientific | 2007 |
| India Gate Chichester Limited | Hospitality | 2007 |
| Industrial Computers Europe Limited | Professional & scientific | 2006 |
| Infrakarn Limited | Households | 1986 |
| Inoma Ltd | Professional & scientific | 2002 |
| Inputplus Limited | Information & communication | 1996 |
| Insideout Home & Garden Improvements Limited | Administrative & support | 2006 |
| Installations Pro Limited | Construction | 2005 |
| Instone Holdings Limited | Transport & logistics | 1988 |
| Intaglio Communications Limited | Manufacturing | 2000 |
| Internal Workings Limited | Wholesale & retail | 1998 |
| International Supplies Limited | Wholesale & retail | 2008 |
| Invictor Limited | Professional & scientific | 2006 |
| Isham Builders Limited | Construction | 2002 |
| IT Presentations Limited | Extraterritorial | 1995 |
| Itchenor Gate Farms | Agriculture & fishing | 1962 |
| Itchenor Sailing Club Limited | Arts & recreation | 1931 |
| Ivan Baker Limited | Construction | 2003 |
| Ivan P&P Ltd | Administrative & support | 2016 |
| J a K Garden Services Ltd | Construction | 2025 |
| J P Supplies (Crawley) Limited | Wholesale & retail | 2000 |
| J R C Carpentry Limited | Construction | 2005 |
| J. Kilby Limited | Arts & recreation | 1991 |
| J.P. Taffe Decorating Ltd. | Construction | 1997 |
| J.W.Stratton Limited | Construction | 1940 |
| Jack Goatcher Fitness & Performance Ltd | Education | 2025 |
| Jackson-Stops & Staff (Southern) Limited | Real estate | 1992 |
| Jacobs and Hunt Fine Art Auctioneers Limited | Administrative & support | 2004 |
| Jacobs Steel & Co. Limited | Real estate | 2006 |
| Jamaica Dreams Limited | Administrative & support | 1988 |
| Jantec Limited | Information & communication | 1998 |
| Jaston Engineering Limited | Professional & scientific | 2007 |
| JC Dunt Fire & Security Limited | Construction | 2002 |
| JC Polishing Limited | Manufacturing | 2002 |
| JCP Consultancy & Talent Search Limited | Professional & scientific | 2019 |
| JET Black Aviation Services Limited | Professional & scientific | 2003 |
| JET Black Group Limited | Professional & scientific | 2003 |
| JET Marine UK Limited | Transport & logistics | 2005 |
| JET Wash Aircraft Cleaning Ltd | Transport & logistics | 2001 |
| Jewelrecall Limited | Manufacturing | 1990 |
| JI Brighton Ltd | Hospitality | 2023 |
| JM Fast Foods Ltd | Hospitality | 2021 |
| JO Mcilvenna Limited | Professional & scientific | 2006 |
| Jobfiliate Ltd | Administrative & support | 2004 |
| Jocopro Limited | Real estate | 2020 |
| JPM Community Care Services Ltd | Administrative & support | 2002 |
| JRJ Fire Security & Maintenance Ltd | Construction | 2004 |
| JRT Estate Services Ltd | Administrative & support | 2005 |
| JST Plumbing & Heating Ltd | Professional & scientific | 2026 |
| Julian Church & Associates Limited | Professional & scientific | 2001 |
| Julian Hill Consulting Limited | Professional & scientific | 2007 |
| Julian Worskett Design Limited | Professional & scientific | 1994 |
| Junction Mews Management Company Limited | Households | 2004 |
| Junction SP1CE Limited | Hospitality | 2024 |
| Just Skin Beauty Consulting Ltd | Health & social care | 2025 |
| K Stephenson Heating Services Limited | Construction | 2003 |
| K. & J. Limited | | 1987 |
| K.A. Ballard Associates Ltd | Professional & scientific | 1998 |
| K.A. Exporters Limited | Wholesale & retail | 2006 |
| K.E. Wood (Management Services) Limited | | 1982 |
| K.P.S. Contractors Limited | Administrative & support | 1988 |
| Kahrs (UK) Limited | Wholesale & retail | 1971 |
| Karen Ashworth Consulting Limited | Professional & scientific | 2000 |
| Karl Thomson Decorating Ltd | Professional & scientific | 2005 |
| Keenhope Limited | Construction | 1989 |
| Keith Best Electrical Contractors Limited | Construction | 2005 |
| Keith Langmead (Arundel) Limited | Agriculture & fishing | 1950 |
| Kelgray Holdings Limited | Real estate | 2005 |
| Kemp Consultants Limited | Administrative & support | 1989 |
| Kerstin James Limited | Professional & scientific | 2008 |
| Kevin Edland Lighting Limited | Other services | 2001 |
| Kevin Holland and Sons Limited | Other services | 2002 |
| Kevin Wheelhouse Ltd | Wholesale & retail | 2004 |