| J109 Racing Limited | Administrative & support | 2016 |
| J2IT Limited | Information & communication | 2012 |
| J316 Ltd | Hospitality | 2021 |
| J4 Executive Ltd | Professional & scientific | 2016 |
| J4OM Limited | Professional & scientific | 2025 |
| J9D Imaging Limited | Professional & scientific | 2015 |
| JA Construction (London) Limited | Construction | 2012 |
| JA Fostering Ltd | Health & social care | 2024 |
| Jabr Holdings Ltd | Real estate | 2024 |
| Jack and Jolly Limited | Wholesale & retail | 2023 |
| Jack Campbell Spray Painting Ltd | Construction | 2025 |
| Jack Clark Services Limited | Information & communication | 2026 |
| Jack Ellison Ltd | Financial services | 2026 |
| Jack Jarvis Enterprises Ltd | Arts & recreation | 2024 |
| Jack Kempton Golf Ltd | Education | 2024 |
| Jack M Smith Construction Site Services Limited | Construction | 2015 |
| Jack on the Water Ltd | Other services | 2023 |
| Jackaroo UK PTY Ltd | Administrative & support | 2022 |
| Jackeline Properties Limited | Real estate | 2023 |
| Jackie Pomroy Consultancy Ltd | Professional & scientific | 2016 |
| Jacks Prime Ltd | Hospitality | 2026 |
| Jackson Arenas Limited | Administrative & support | 2013 |
| Jackson Construction (Southcoast) Ltd | Construction | 2023 |
| Jackson IP Limited | Real estate | 2013 |
| Jackson Signature Stays Ltd | Hospitality | 2025 |
| Jaclan Masonry Ltd | Construction | 2017 |
| Jacob & Sons Holdings Ltd | Real estate | 2021 |
| Jacobi Ventures UK Ltd | Administrative & support | 2007 |
| Jacperls Ltd | Real estate | 2020 |
| Jacques Pet Care Services Ltd | Professional & scientific | 2024 |
| Jacqui Thornton Communications Ltd | Professional & scientific | 2014 |
| Jada Agency Limited | Professional & scientific | 2008 |
| Jade Seal Limited | Health & social care | 2015 |
| JAF Consulting Limited | Information & communication | 2022 |
| JAG (C & I) Engineering Limited | Manufacturing | 1997 |
| JAG Creative Ltd | Professional & scientific | 2023 |
| Jagre Ltd | Construction | 2018 |
| Jags Architechs Limited | Professional & scientific | 2008 |
| Jahin Music Limited | Wholesale & retail | 2024 |
| JAI Jagannath JI Ltd | Hospitality | 2025 |
| JAI P Consultancy Services Limited | Professional & scientific | 2013 |
| Jaicom Ltd | Health & social care | 2022 |
| Jaidhill Properties Ltd | Real estate | 2025 |
| Jaig Holdings Ltd | Real estate | 2025 |
| Jaimini Patel Limited | Health & social care | 2016 |
| JAJ Heating Services Ltd | Construction | 2018 |
| JAK Property Holdings Limited | Arts & recreation | 2006 |
| Jakpa UK Ltd | Extraterritorial | 2023 |
| Jakub Trans Ltd | Transport & logistics | 2016 |
| Jalf Solutions Limited | Wholesale & retail | 2019 |
| Jalfrezy Ltd | Hospitality | 2026 |
| Jalu Dental Company Ltd | Health & social care | 2021 |
| JAM Accounting Ltd | Professional & scientific | 2016 |
| JAM Electrical (Southampton) Ltd | Construction | 2013 |
| JAM JAR Leisure Ltd | Hospitality | 2015 |
| JAM Kare Services Ltd | Health & social care | 2020 |
| JAM Sack Games Limited | Manufacturing | 2023 |
| JAM Stage Hire Ltd | Administrative & support | 2019 |
| JAM Stage Holdings Ltd | Financial services | 2021 |
| Jamba Developments Limited | Construction | 2024 |
| Jamba Enterprises Limited | Hospitality | 2004 |
| Jamba Estates Limited | Hospitality | 2011 |
| Jamba Holdings Limited | Real estate | 2018 |
| Jamba Land Limited | Real estate | 1983 |
| Jamba Leisure Limited | Real estate | 2021 |
| Jamba Maintenance Limited | Real estate | 1990 |
| Jamba Otterbourne Limited | Hospitality | 2024 |
| Jamba Projects Limited | Real estate | 1972 |
| Jamba Residential Limited | Real estate | 2024 |
| Jamerella Limited | Extraterritorial | 2011 |
| James & Withers Limited | Construction | 2009 |
| James Andrews Limited | Professional & scientific | 2004 |
| James Beacroft Limited | Other services | 2013 |
| James Bellini Associates Limited | Arts & recreation | 1981 |
| James C Films TV Ltd | Information & communication | 2020 |
| James Consulting Ltd | Professional & scientific | 2025 |
| James Cowper Services Limited | Professional & scientific | 2009 |
| James Dean Harrigan Ltd | Information & communication | 2025 |
| James Diggens Auto Services Limited | Wholesale & retail | 2014 |
| James Edwards Partnership Ltd | Households | 2025 |
| James Grace Groundwork and Construction Limited | Construction | 2013 |
| James Grigg Limited | Health & social care | 2015 |
| James Hill Mortgages & Protection Ltd | Financial services | 2024 |
| James Hocking Wine Limited | Wholesale & retail | 2019 |
| James Huntley & Sons Ltd. | Wholesale & retail | 1996 |
| James Leonard Ltd | Professional & scientific | 2017 |
| James Liston Building Services Ltd | Construction | 2016 |
| James Liston Electrical Ltd | Construction | 2022 |
| James Liston Holdings Ltd | Financial services | 2021 |
| James Read Limited | Extraterritorial | 2016 |
| James Shadick Ltd | Professional & scientific | 2022 |
| James Spencer Marine Ltd | Manufacturing | 2022 |
| James Thomas Holdings Limited | Financial services | 2025 |
| James Watt Marina Limited | Real estate | 2016 |
| Jamesb Logistics Ltd | Transport & logistics | 2025 |
| Jameshugohickman Ltd | Administrative & support | 2025 |
| Jamie Deakin Design Limited | Information & communication | 2017 |
| Jamie FRY Equestrian Limited | Arts & recreation | 2025 |
| Jamie Motors Trading Ltd | Wholesale & retail | 2021 |
| Jamie Stewart Ltd | Wholesale & retail | 2025 |