| Interfin Partner Limited | Administrative & support | 2021 |
| International Driver Coaching Group Ltd | Arts & recreation | 2026 |
| International Location Safety Limited | Professional & scientific | 2015 |
| International Programme on the State of the Ocean | Professional & scientific | 2007 |
| Internet Golf Holidays Ltd | Professional & scientific | 2007 |
| Intrepid Consulting Limited | Information & communication | 2007 |
| Inverglen Capital Limited | Professional & scientific | 2024 |
| Investment Dwellings Ltd | Real estate | 2025 |
| Investwise Asset Management Limited | Financial services | 2006 |
| ION Swarm Ltd | Information & communication | 2025 |
| Iosbio Ltd | Health & social care | 2002 |
| IP Sentinel Limited | Information & communication | 2013 |
| Ipft Fuels Limited | Professional & scientific | 2013 |
| Ipxchange.Tech Limited | Wholesale & retail | 2022 |
| Iqurate Ltd | Information & communication | 2024 |
| Island Retail Trading Co Ltd | Wholesale & retail | 2022 |
| Islands of Greece Limited | Administrative & support | 1964 |
| Istanbul Barbers RH Ltd | Other services | 2021 |
| Isted Edition Ltd | Professional & scientific | 2025 |
| Istrive Limited | Professional & scientific | 2022 |
| Isymo Consultancy Ltd | Professional & scientific | 2025 |
| Italent Associates Ltd | Administrative & support | 2014 |
| Itconsilium Limited | Information & communication | 1994 |
| ITE Developments Ltd | Construction | 2013 |
| Itfc Ltd | Information & communication | 2023 |
| IV01 Limited | Real estate | 2021 |
| IV02 Limited | Manufacturing | 2025 |
| Ives & Associates Limited | Professional & scientific | 2026 |
| IVY Leased Assets Limited | Administrative & support | 2014 |
| Iwi.Earth Ltd | Information & communication | 2018 |
| J & D Foster Farms LLP | | 2011 |
| J & RD Media Ltd | Professional & scientific | 2022 |
| J & Z Developments Ltd | Administrative & support | 2021 |
| J Cragg Contractors Ltd | Construction | 2022 |
| J D Givons Limited | Administrative & support | 2005 |
| J D S Property Consultancy Limited | Professional & scientific | 2025 |
| J Douglas Consulting Ltd | Professional & scientific | 2018 |
| J Langabeer Limited | Households | 2008 |
| J Nieboer Consulting Ltd | Professional & scientific | 2024 |
| J P (Holdings) Limited | Real estate | 1992 |
| J Pain Consultancy Limited | Other services | 2012 |
| J R Digital Services Limited | Information & communication | 2008 |
| J Raymond Security Ltd | Construction | 2018 |
| J S Rothwell Consulting Limited | Professional & scientific | 2013 |
| J Unwin Property and Construction Limited | Construction | 2017 |
| J V Lawrence Ltd | Real estate | 2022 |
| J&S (Sussex) Limited | Construction | 2016 |
| J&W Bodywork Specialists Ltd | Wholesale & retail | 2024 |
| J. & J. Smith (Holdings) Limited | Financial services | 1987 |
| J. & J. Smith (Investments) Limited | Financial services | 1987 |
| J. Bayles Ltd | Information & communication | 2006 |
| J. Bourne Plant Repairs Ltd | Manufacturing | 2005 |
| J.B.C. Crawley Industrial Services Limited | Transport & logistics | 1973 |
| J.Cheal & Sons,Limited | Real estate | 1912 |
| J.Dunne Plumbing and Heating Ltd | Other services | 2018 |
| J.P.H.F. (U.K.) Limited | Real estate | 1981 |
| J.V.R Sussex Limited | Wholesale & retail | 2020 |
| JA Commercial Services Limited | Professional & scientific | 2001 |
| Jack's JET Washing 1 Ltd | Administrative & support | 2024 |
| Jackson Design Studio Ltd | Professional & scientific | 2020 |
| Jajr Investments (UK) Limited | Wholesale & retail | 2004 |
| Jake Ridley Holdings Ltd | Financial services | 2025 |
| Jake White Architecture Ltd | Professional & scientific | 2024 |
| JAL ACC Ltd | Professional & scientific | 2010 |
| Jalisa Consultancy Limited | Health & social care | 2011 |
| James Allen IT Limited | Information & communication | 2018 |
| James Developers Limited | Professional & scientific | 2013 |
| James Hughes Gardens Limited | Administrative & support | 2024 |
| James Petherick Limited | Arts & recreation | 2014 |
| James Rose Kitchens & Developments Limited | Construction | 2014 |
| James Turzynski Animation & Design Ltd. | Professional & scientific | 2016 |
| Jane Kirton Consulting Limited | Professional & scientific | 2013 |
| Janis Consulting Ltd | Information & communication | 2022 |
| Jasie Ltd | Real estate | 2012 |
| Jasper Surveying & Construction Services Ltd | Professional & scientific | 2018 |
| Jaunty Gents Ltd | Other services | 2023 |
| Jaynaya Limited | Health & social care | 2024 |
| JB Access & Security Ltd | Administrative & support | 2024 |
| JC GEM Ltd | Manufacturing | 2026 |
| JC IT Consultancy Limited | Information & communication | 2008 |
| JD Audit Services Limited | Professional & scientific | 2012 |
| JDA Wright Consulting Limited | Professional & scientific | 2016 |
| JDL Letting Ltd | Real estate | 2017 |
| JDS Property Investment Limited | Real estate | 2026 |
| JEH Tech Ltd | Information & communication | 2025 |
| JEM Live Ltd | Professional & scientific | 2020 |
| Jenkinsons Bespoke Joinery Limited | Construction | 2010 |
| Jenny Mclachlan Limited | Administrative & support | 2014 |
| Jestfun Limited | Construction | 1988 |
| Jetworld Limited | Manufacturing | 1999 |
| JEX Consulting Ltd | Professional & scientific | 2025 |
| JF Carpentry Contracts Limited | Construction | 2017 |
| JFS & Go Property Ltd | Construction | 2019 |
| Jg’S Hospitality Ltd Limited | Hospitality | 2020 |
| JIC Investments Limited | Real estate | 2018 |
| Jimmys Barbers Cuckfield Limited | Other services | 2018 |
| Jimmys Property Care Ltd | Administrative & support | 2025 |
| JIP Properties Limited | Real estate | 2025 |
| JJA Property Investments Limited | Financial services | 2017 |
| JJH Services Ltd | Construction | 2024 |