| IVC Print Club Ltd | Financial services | 2019 |
| Ivoxx Ltd | Administrative & support | 2025 |
| Ivyhill Ltd | Construction | 2019 |
| IX Holdings Ltd | Professional & scientific | 2018 |
| J & a Design Studios Ltd | Professional & scientific | 2025 |
| J & D Southern Ltd | Hospitality | 2013 |
| J & J Conversions International Limited | Extraterritorial | 2025 |
| J a Brands Limited | Real estate | 2017 |
| J C & E (UK) LLP | | 2012 |
| J C & E Limited | Professional & scientific | 2011 |
| J C LE Roux Properties Limited | Professional & scientific | 2001 |
| J Design and Planning Limited | Professional & scientific | 2009 |
| J Hillier Building Services Limited | Construction | 2006 |
| J J S Holding Limited | Administrative & support | 2017 |
| J R Brown Plumbing & Heating Services Limited | Construction | 2004 |
| J Russell Electrical Ltd | Construction | 2015 |
| J S Apple Holdings Ltd | Real estate | 2017 |
| J Stokoe Installation Ltd | Manufacturing | 2018 |
| J T Cabins Limited | Wholesale & retail | 2012 |
| J Weston Limited | Construction | 2024 |
| J&A Hope Developments Ltd | Construction | 2026 |
| J&A Hope Property Ltd | Real estate | 2024 |
| J&J Martin LLP | | 2012 |
| J&K Bamboo Holdings Ltd | Hospitality | 2017 |
| J&Ls Consultancy Limited | Arts & recreation | 2025 |
| J'S Subs Limited | Wholesale & retail | 2007 |
| J. R. Fisher Limited | Manufacturing | 2003 |
| J. Skene Roofing Limited | Construction | 2017 |
| J.A. Engineering (Southern) Limited | Manufacturing | 1997 |
| J.C. Ransom Garages Limited | Real estate | 1959 |
| J.Couper TM Ltd | Construction | 2025 |
| J.E.R Accounting Services Limited | Professional & scientific | 2003 |
| J.Farooq TM Ltd | Construction | 2025 |
| J.L.Terrell Ltd | Professional & scientific | 2026 |
| J.R. Moore & Sons Limited | Construction | 2002 |
| JA Ecology Ltd | Professional & scientific | 2021 |
| Jaasmar Consulting Ltd | Health & social care | 2026 |
| JAC Construction Services Ltd | Construction | 2015 |
| JAC in the Knox Limited | Real estate | 2014 |
| Jacj Holdings Ltd | Real estate | 2025 |
| Jafari Commercial Ltd | Real estate | 2020 |
| Jake Allert Capital Ltd | Construction | 2025 |
| Jake Allert Property Management Ltd | Real estate | 2025 |
| Jaks House & Home Ltd | Construction | 2022 |
| JAM Electrical & Property Services Limited | Construction | 2022 |
| James Beattie Football Academy Limited | Arts & recreation | 2025 |
| James COX Electrical Limited | Construction | 2026 |
| James Houlston Ltd | Manufacturing | 2023 |
| Janousek and Stampfli Boats Ltd | Manufacturing | 2021 |
| JAR Carpentry Ltd | Manufacturing | 2024 |
| Jart Properties Ltd | Real estate | 2017 |
| Jarvis Plant & Fleet Services Ltd | Administrative & support | 2022 |
| Jase Holdings (UK) Ltd | Financial services | 2023 |
| Jasmine Consulting (UK) Limited | Professional & scientific | 2009 |
| Jason Pooley Coaching & Consulting Ltd | Education | 2023 |
| Jason Williams Limited | Construction | 2015 |
| Jasrose Limited | Other services | 2024 |
| Jathesam Limited | Professional & scientific | 2019 |
| Jatt Haulage Ltd | Transport & logistics | 2017 |
| Jaya Property Ltd | Real estate | 2020 |
| Jayakody and Daughters Property Management Ltd | Real estate | 2022 |
| Jaykarafit Ltd | Administrative & support | 2019 |
| JBL Moore Ltd | Wholesale & retail | 2023 |
| Jc&Rc Ltd | Real estate | 2026 |
| JC' Scapes Limited | Administrative & support | 2007 |
| Jcbreaksandchase Ltd | Wholesale & retail | 2025 |
| Jcems Limited | Administrative & support | 2008 |
| Jcrc Holdings Limited | Financial services | 2024 |
| Jcsl Group Ltd | Arts & recreation | 2021 |
| JDC Consultancy Services Limited | Professional & scientific | 2025 |
| JDJ Scaffolding Ltd | Construction | 2022 |
| JDL Property Investments Ltd | Real estate | 2022 |
| JDL Property Management Services Ltd | Real estate | 2022 |
| JDM International Investments Limited | Professional & scientific | 2022 |
| Jdra Consultancy Ltd | Professional & scientific | 2018 |
| JE Hobbs Limited | Administrative & support | 2014 |
| JE Innovations Ltd | Information & communication | 2025 |
| JE Montague & SON Ltd | Professional & scientific | 2026 |
| Jedi Sales Consultants Limited | Wholesale & retail | 2020 |
| Jegs Marine Limited | Professional & scientific | 2015 |
| Jelly West Property Limited | Real estate | 2015 |
| Jemma George Hair Artistry Ltd | Other services | 2006 |
| Jenpas Solutions Limited | Health & social care | 2023 |
| Jess Lorimer Ltd | Professional & scientific | 2014 |
| Jessica Hyde-Brown Limited | Other services | 2003 |
| Jessica Perkins Business Services Limited | Professional & scientific | 2019 |
| Jetasupport Limited | Professional & scientific | 2012 |
| Jett Projects Management Ltd | Professional & scientific | 2026 |
| JFD Comms Ltd | Construction | 2018 |
| JFG Accountancy & Finance Ltd | Professional & scientific | 2025 |
| JFP Pro-Sprays Ltd | Manufacturing | 2017 |
| JFS Finance Limited | Financial services | 2010 |
| JG Rail Consultants Limited | Professional & scientific | 2026 |
| JG Signalling Solutions Ltd | Construction | 2018 |
| JGB Auto Consulting Ltd | Wholesale & retail | 2020 |
| JGV Holdings Group Ltd | Health & social care | 2026 |
| JGY Consulting Ltd | Professional & scientific | 2025 |
| JH Building and Carpentry Ltd | Other services | 2019 |
| Jh&Jp Holdings Ltd | Professional & scientific | 2024 |
| JHC Automotive Bodywork Ltd | Wholesale & retail | 2023 |