| Ivimy Consulting Ltd | Wholesale & retail | 2015 |
| Ivory Touch Nail Studio Ltd | Other services | 2026 |
| IX Limited | Agriculture & fishing | 2010 |
| J and C Foster Limited | Administrative & support | 1969 |
| J and R Parker LLP | | 2008 |
| J B Walsh Pipefitting Limited | Manufacturing | 2014 |
| J Creaney Limited | Professional & scientific | 2011 |
| J Cruz Ltd | Professional & scientific | 2014 |
| J D E Business Services Limited | Professional & scientific | 2014 |
| J D Systems (South) Ltd | Construction | 2011 |
| J F M G Limited | Information & communication | 1996 |
| J G Pipeline Consultancy Ltd | Professional & scientific | 2006 |
| J M Rees Surveying Ltd | Professional & scientific | 2026 |
| J Marsh Services Limited | Real estate | 2014 |
| J Molton & SON Limited | Wholesale & retail | 2011 |
| J Nicholson Fencing Limited | Administrative & support | 2023 |
| J NYE Plumbing & Heating Ltd | Construction | 2025 |
| J S Chevalier Limited | Financial services | 2019 |
| J White Developments Ltd | Construction | 2020 |
| J&A PAY Ltd | Administrative & support | 2023 |
| J&B Evertrade Ltd | Wholesale & retail | 2017 |
| J. G. Venn Limited | Agriculture & fishing | 1999 |
| J. T. Electrical Services Limited | Construction | 2005 |
| J.H.Watling(Developments)Limited | Construction | 1960 |
| J.J.&M.Habel Limited | Wholesale & retail | 1960 |
| J.R. Sykes Farms | Agriculture & fishing | 1973 |
| J.T Mitchell Enterprise Limited | Water & waste | 2023 |
| J7M3 Ltd | Other services | 2014 |
| JA Promotions Ltd | Professional & scientific | 2025 |
| Jackdaw Films Limited | Information & communication | 2013 |
| Jackson Products Limited | Extraterritorial | 2019 |
| Jacon Enterprises Limited | Wholesale & retail | 2024 |
| Jade Invest UK Limited | Professional & scientific | 2014 |
| Jade LIN Limited | Hospitality | 2024 |
| JAGO8 Descon Ltd | Professional & scientific | 2020 |
| JAH Cleaning Services Limited | Water & waste | 2014 |
| JAK Meridian Ltd | Professional & scientific | 2026 |
| Jakeydavies Ltd | Information & communication | 2025 |
| Jalport Limited | Professional & scientific | 2017 |
| James David Land Profits Ltd | Real estate | 2025 |
| James Lamont Associates Limited | Other services | 2016 |
| James Rampton Limited | Administrative & support | 2003 |
| James W Thomas Limited | Real estate | 2014 |
| JAN M Music Ltd | Arts & recreation | 2014 |
| Janne Ltd | Wholesale & retail | 2026 |
| Janovo Limited | Professional & scientific | 2012 |
| Jardineoates Limited | Administrative & support | 2020 |
| Jasper Gooding Tree Services Limited | Agriculture & fishing | 2018 |
| Jasper Tech Ltd | Information & communication | 2024 |
| Javajava London Limited | Hospitality | 2015 |
| Javajava Petersfield Limited | Hospitality | 2015 |
| JB Artist Management Ltd | Information & communication | 2017 |
| JBM1 Ltd | Information & communication | 2024 |
| JC Clinical Research Consulting Ltd | Professional & scientific | 2024 |
| JC Dog Sitting Ltd | Other services | 2026 |
| Jcat Enigma Park Limited | Real estate | 2018 |
| Jcat Lightwood Land Shares Ltd | Real estate | 2018 |
| Jcew Properties Limited | Real estate | 2022 |
| JCM Glass and Glazing Limited | Construction | 2015 |
| JCR Procurement Ltd | Real estate | 2019 |
| JD Admin Limited | Administrative & support | 2025 |
| Jdei Limited | Financial services | 2023 |
| Jearo Limited | Manufacturing | 2019 |
| Jefferies & Company Limited | Professional & scientific | 2009 |
| Jellywire Aviation Ltd | Professional & scientific | 2025 |
| Jenkins Utilities Limited | Construction | 2019 |
| Jenni Spencer Limited | Information & communication | 2006 |
| Jennings Asset Management Limited | Extraterritorial | 2014 |
| Jennings Wealth Management Limited | Financial services | 2010 |
| Jensen Service Ltd | Wholesale & retail | 2020 |
| Jeremy Robinson at the Consortium Limited | Wholesale & retail | 2005 |
| Jessica Hartley Creative Ltd | Professional & scientific | 2019 |
| Jettyland Ltd | Real estate | 2018 |
| JFK Electrical Contractors Limited | Extraterritorial | 2018 |
| Jfrancis Properties Ltd | Real estate | 2021 |
| JH Props Ltd | Arts & recreation | 2008 |
| JJG Consulting International Limited | Professional & scientific | 2015 |
| JJJ Holdco Limited | Professional & scientific | 2023 |
| JJR Investments Ltd | Real estate | 2026 |
| JJS Fine Art Limited | Arts & recreation | 2016 |
| JJW CAD Solutions Ltd | Professional & scientific | 2015 |
| JK Property Management & Maintenance Holdings Ltd | Real estate | 2024 |
| JK Property Management & Maintenance Ltd | Real estate | 2012 |
| JK Service Design Limited | Manufacturing | 2026 |
| JLS Pizza Ltd | Hospitality | 2018 |
| JLT Catering Limited | Extraterritorial | 2023 |
| JLW Winchester LLP | | 2013 |
| JM & Sons Roofing & Guttering Services Ltd | Construction | 2025 |
| JM Training Solutions Limited | Information & communication | 2019 |
| JM13 Promotions Limited | Arts & recreation | 2018 |
| JM13 Properties Limited | Real estate | 2023 |
| Jmlk Construction Ltd | Construction | 2024 |
| JMN Investment Ltd | Real estate | 2016 |
| Joalex Properties Ltd | Real estate | 2022 |
| Joanne Bowles Holdings Limited | Real estate | 2025 |
| Joanne Bowles Jewellery Limited | Manufacturing | 2025 |
| John Goodey Coaching Ltd | Education | 2021 |
| John King Limited | Manufacturing | 1998 |
| John Langmead Ltd | Agriculture & fishing | 2018 |
| John O'Neill Associates Limited | Administrative & support | 2001 |