| Iter Orior Limited | Information & communication | 2024 |
| Itertech Limited | Information & communication | 2022 |
| Itis Consulting Limited | Information & communication | 2009 |
| Itsfood Ltd | Hospitality | 2023 |
| Itthread Limited | Information & communication | 2009 |
| Ivarsec Ltd | Construction | 2016 |
| Ivory Apparel Ltd | Wholesale & retail | 2018 |
| Ivory Group Limited | Real estate | 2015 |
| Ivory Projects Ltd. | Construction | 2013 |
| Ivory Property Services Limited | Professional & scientific | 2019 |
| Ivory Thread Ltd | Wholesale & retail | 2025 |
| IVS Assets Limited | Arts & recreation | 2026 |
| IVY Landscapes Ltd | Other services | 2007 |
| IW Props Ltd | Information & communication | 2020 |
| IWS (Industrial & Welding Supplies) Limited | Professional & scientific | 2008 |
| IZA Bella Limited | Manufacturing | 2019 |
| Izco Trading Limited | Wholesale & retail | 2026 |
| J & P Dodsworth Limited | Other services | 2009 |
| J & R Contractors Limited | Construction | 2008 |
| J & R Stewart Consultancy Services Ltd | Professional & scientific | 2023 |
| J & S Cleanco Limited | Wholesale & retail | 1986 |
| J and J Electrical and Instrumentation Ltd | Manufacturing | 2020 |
| J Bath Surfacing Limited | Construction | 2017 |
| J Best Building Services Limited | Construction | 2003 |
| J C Amusements Limited | Administrative & support | 2010 |
| J Calzi Building Services Ltd | Construction | 2018 |
| J D Recruitment Ltd | Professional & scientific | 2025 |
| J Grace Services Limited | Education | 2019 |
| J Hanc Limited | Professional & scientific | 2014 |
| J L Butchers Ltd | Wholesale & retail | 2013 |
| J Lewis Lighting Limited | Other services | 2014 |
| J P Airconditioning Ltd | Manufacturing | 2019 |
| J Whitby Consulting Ltd | Professional & scientific | 2022 |
| J&J Golf Services Ltd | Other services | 2018 |
| J&L Golf Repairs Ltd | Manufacturing | 2025 |
| J&Mconsulting Limited | Real estate | 2021 |
| J-Pulcher Limited | Health & social care | 2025 |
| J. Hartley Antiques Limited | Wholesale & retail | 1973 |
| J. Toop Associates Limited | Professional & scientific | 1997 |
| J.A. Calvo Limited | Other services | 2020 |
| J.E & SON Roofing Ltd | Construction | 2019 |
| J.H.Moore Consultants Ltd | Professional & scientific | 2024 |
| J.U.M.P. Services Limited | Wholesale & retail | 1994 |
| J.W.Elliott & Sons (West END) Limited | Wholesale & retail | 1962 |
| J2J Events Ltd | Information & communication | 2018 |
| Jack & Jill`S Day Nursery Limited | Education | 2004 |
| Jacket & Co London Limited | Wholesale & retail | 2021 |
| Jackets & Juices Ltd | Other services | 2019 |
| Jackie Bonella Limited | Professional & scientific | 2006 |
| Jackman's Lodge Ltd | Health & social care | 2011 |
| Jackmans & Sons Ltd | Real estate | 2015 |
| Jackota Systems Limited | Wholesale & retail | 2023 |
| Jade Events Ltd | Hospitality | 2024 |
| Jafferies CA Ltd | Professional & scientific | 2010 |
| Jaiq Homes Limited | Construction | 2011 |
| JAM Space Ltd | Real estate | 2023 |
| Jamello Limited | Other services | 2009 |
| James Engineering Services Ltd | Professional & scientific | 2008 |
| James Irvin Ltd | Real estate | 2013 |
| James Painting and Renovation Ltd | Construction | 2026 |
| James Riches Limited | Construction | 2013 |
| James Stuart Designs Limited | Manufacturing | 2007 |
| James Sunshine Film Services Ltd | Information & communication | 2020 |
| James Walker & Co. Limited | Manufacturing | 1989 |
| James Walker Group Limited | Professional & scientific | 1921 |
| James Walker Metaflex Limited | Professional & scientific | 1948 |
| James Walker Nominees Limited | Professional & scientific | 2000 |
| James Walker Sealing Products & Services Limited | Administrative & support | 1932 |
| James Walker Teadit Limited | Professional & scientific | 2014 |
| James Walker Trustees Limited | Professional & scientific | 1995 |
| James Walker UK Limited | Wholesale & retail | 2010 |
| James Walker Viceroy Limited | Real estate | 1957 |
| James Williamson Architects Ltd | Professional & scientific | 2023 |
| Jamieson Kemp Limited | Hospitality | 2013 |
| Jamspurs Limited | Extraterritorial | 2017 |
| Jane Fordham Consulting Ltd | Professional & scientific | 2018 |
| Jane's Pet Care Services Ltd | Professional & scientific | 2006 |
| Janela Inversiones Ltd | Education | 2018 |
| Janoway Hill Management Company Limited | Households | 2009 |
| Jariwala Waldemar Ltd | Information & communication | 2024 |
| Jarred Consulting Limited | Professional & scientific | 2007 |
| Jashar LLP | | 2023 |
| Jasmine Project Holdings Limited | Real estate | 2025 |
| Jason Carder Limited | Construction | 2004 |
| Jass Property Rentals Ltd | Real estate | 2018 |
| JAW Business Services Limited | Professional & scientific | 2002 |
| Jaye Bird Aesthetics Limited | Other services | 2017 |
| Jayling Limited | Hospitality | 2015 |
| Jayrise Limited | Real estate | 2017 |
| Jazland Ltd | Real estate | 2024 |
| JB Marine Sales Ltd | Wholesale & retail | 2018 |
| JBF Garden Maintenance Ltd | Administrative & support | 2025 |
| JBF Tree Surgery Ltd | Agriculture & fishing | 2025 |
| JBH Group Limited | Construction | 2020 |
| JC Motorz Limited | Wholesale & retail | 2025 |
| JCH Property Holdings Ltd | Real estate | 2017 |
| JCL Property Maintenance Ltd | Construction | 2024 |
| Jctfrancis Ltd | Professional & scientific | 2026 |
| JD & LK Golding Ltd. | Hospitality | 2013 |
| JD Pro Development Ltd | Real estate | 2021 |