| Ishy Limited | Information & communication | 2015 |
| Island Financial Strategy LLP | | 2007 |
| Island FS Ltd | Financial services | 2020 |
| ISN Group Ltd | Professional & scientific | 2021 |
| ISN Medical Ltd | Wholesale & retail | 2020 |
| Isnoda Group Limited | Other services | 2026 |
| Isurus Limited | Administrative & support | 2000 |
| IT Problem Service Consultants Ltd | Professional & scientific | 2024 |
| Itpm Consultancy Limited | Information & communication | 2006 |
| Itswilliamcharles Limited | Wholesale & retail | 2021 |
| Ivory Tusk Services Ltd | Health & social care | 2025 |
| IVY Farm Padbury Limited | Households | 2001 |
| J & H Actuarial Services Limited | Professional & scientific | 2012 |
| J & J S Mcneil Limited | Health & social care | 2008 |
| J a Hannon & Co Limited | Professional & scientific | 2010 |
| J B Clothing Limited | Wholesale & retail | 2010 |
| J B Pro Ltd | Real estate | 2019 |
| J Baughan Roofing Ltd | Construction | 2024 |
| J Fossey Plastering Ltd | Construction | 2015 |
| J Pankhurst Construction Ltd | Construction | 2024 |
| J S Gibson Limited | Construction | 2012 |
| J White Builders Ltd | Construction | 2017 |
| J White Properties Ltd | Real estate | 2018 |
| J&J Bespoke Electrical Limited | Construction | 2015 |
| J&Ji Limited | Real estate | 2021 |
| J&K Fitness Limited | Arts & recreation | 2024 |
| J&M Brothers Properties Ltd | Real estate | 2020 |
| J.T.L Productions Ltd | Information & communication | 2015 |
| Jack Richardson Architecture Ltd | Professional & scientific | 2022 |
| Jackdaw Consultants Limited | Administrative & support | 2016 |
| Jackdaw Music Services Ltd | Arts & recreation | 2023 |
| JAG Construct Ltd | Construction | 2025 |
| Jake Brough Fitness Ltd | Education | 2022 |
| Jalt Services Limited | Professional & scientific | 2012 |
| Jambo Jewellery Limited | Wholesale & retail | 2011 |
| James Bull Carpentry Limited | Manufacturing | 2015 |
| James Tattam Joinery Limited | Construction | 2005 |
| Jamieson Devices Limited | Manufacturing | 2016 |
| Jaqua Solutions Limited | Hospitality | 2012 |
| Jaqui Bursnall Design Limited | Professional & scientific | 2021 |
| Jasper&Linen Cleaners Ltd | Administrative & support | 2026 |
| Jassi Building Contractors Ltd | Construction | 2021 |
| JBD Trading Ltd | Manufacturing | 2018 |
| JC Bridges Holding Company Ltd | Financial services | 2024 |
| JCA Assets Limited | Real estate | 2009 |
| Jcch Limited | Transport & logistics | 2008 |
| JCH Media Ltd | Professional & scientific | 2023 |
| JCS Painting Limited | Construction | 2023 |
| JCW Motorsport Ltd | Professional & scientific | 2013 |
| JD SIM Limited | Information & communication | 2024 |
| JDB Plumbing & Heating Services Ltd | Construction | 2025 |
| Jema Developments Limited | Construction | 2009 |
| Jendee Trading Company Limited | Wholesale & retail | 1966 |
| Jenny Draper Ltd | Professional & scientific | 2019 |
| JEP Educational Psychology Ltd | Education | 2023 |
| Jfkb Limited | Health & social care | 2012 |
| Jfkb Properties Ltd | Real estate | 2021 |
| JGC Automotive Limited | Wholesale & retail | 2012 |
| JGG Holdings Ltd | Real estate | 2023 |
| JHD Classic Cars Ltd | Wholesale & retail | 2020 |
| Jigsaw Recruitment Ltd | Extraterritorial | 2015 |
| JJ Groundworks Construction Ltd | Construction | 2019 |
| JJP Film Production Services Ltd | Information & communication | 2019 |
| JKS UK Limited | Manufacturing | 2005 |
| JL Security Consulting Ltd | Administrative & support | 2026 |
| JLR Property Solutions Limited | Real estate | 2024 |
| JLT Property Rentals Limited | Real estate | 2025 |
| JM Property Investment Holdings Ltd | Real estate | 2024 |
| Jm&Co. Recruitment Limited | Administrative & support | 2015 |
| JMR Pallets & Cases Limited | Transport & logistics | 2008 |
| Joanna Craig Website Design Limited | Information & communication | 2012 |
| Joanne Cannon Equestrian Ltd | Education | 2019 |
| Jobnest Recruitment Ltd | Administrative & support | 2025 |
| Joe's Window Cleaning Limited | Administrative & support | 2008 |
| John Collins Electrical Limited | Construction | 2007 |
| John Eccles Transport Services Ltd | Transport & logistics | 2011 |
| John R Powell Engineering Limited | Manufacturing | 2006 |
| John Stubbs Golf Ltd | Arts & recreation | 2012 |
| Jolaj Consulting Ltd | Information & communication | 2023 |
| JON R Spatcher Enterprises Ltd | Administrative & support | 2021 |
| Jonathan Burrows Graphic Design Ltd | Professional & scientific | 2021 |
| Jonny Cater Cricket Academy Ltd | Education | 2022 |
| Joseph Lighting Design Ltd | Professional & scientific | 2018 |
| Joul Ltd | Professional & scientific | 2025 |
| Joyce Property Company Limited | Real estate | 2017 |
| JPM Global Ltd | Wholesale & retail | 2018 |
| JSE Signalling Solutions Ltd | Construction | 2018 |
| JSG Housing Ltd | Real estate | 2026 |
| Jtct Ltd | Real estate | 2017 |
| JTH Events Limited | Hospitality | 2019 |
| JTH Hospitality Limited | Hospitality | 2019 |
| Julian Taylor Solicitors Ltd | Professional & scientific | 2010 |
| Jump Junction Ltd | Other services | 2025 |
| Juno Collective Ltd | Financial services | 2023 |
| Juno Financial Planning Ltd | Professional & scientific | 2023 |
| Jury Properties Ltd | Real estate | 2023 |
| Just the GUY Ltd | Information & communication | 2022 |
| Justcallitanything Ltd | Information & communication | 2024 |
| Juteplace Ltd | Information & communication | 2005 |
| JW Design & Build Ltd | Construction | 2015 |