| Jason Loader QA Consulting Ltd | Professional & scientific | 2025 |
| Jason Tonge Limited | Professional & scientific | 1997 |
| Java Property Ltd | Real estate | 2020 |
| Javsford Holdings Limited | Real estate | 2019 |
| Javsford Investments Limited | Real estate | 1959 |
| JAX Industries Limited | Information & communication | 2016 |
| JAY MAY Property Limited | Real estate | 2023 |
| Jay-Mar Roofing Ltd | Construction | 2018 |
| Jaycom I.T Limited | Other services | 2017 |
| Jaycommerce Limited | Information & communication | 2019 |
| Jazzfone Poole Ltd | Wholesale & retail | 2025 |
| JB Ferndale Ltd | Real estate | 2025 |
| JB Maritime Services Limited | Construction | 2026 |
| JB Trans Express Ltd | Transport & logistics | 2023 |
| JBL Property Maintenance Ltd | Construction | 2020 |
| Jblb Holdings Ltd | Financial services | 2020 |
| JBS Entrepreneurs Limited | Administrative & support | 2024 |
| JBW Coaching Ltd | Professional & scientific | 2019 |
| JC Digital & App Development Limited | Information & communication | 2026 |
| JC Ecommerce UK Ltd | Wholesale & retail | 2024 |
| Jcal Hospitality Ltd | Administrative & support | 2024 |
| Jcdemands Ltd | Wholesale & retail | 2024 |
| JCH Bespoke Detailing Limited | Wholesale & retail | 2026 |
| Jch(Company a) Ltd | Construction | 2017 |
| JCM Corporation Ltd | Wholesale & retail | 2026 |
| JCM Foods Ltd | Hospitality | 2021 |
| JCM SKN Ltd | Health & social care | 2020 |
| JCM US Ltd | Health & social care | 2021 |
| Jcnw Property Management Ltd | Households | 2023 |
| JCR Design Limited | Professional & scientific | 2006 |
| JCS Beacon Hill Limited | Professional & scientific | 2012 |
| JD Building & Carpentry Ltd | Construction | 2021 |
| JD Ecommerce Limited | Information & communication | 2015 |
| JD Home Solutions Ltd | Administrative & support | 2017 |
| JD Radiology Services Ltd | Health & social care | 2023 |
| JD Welding & Fabrication Limited | Professional & scientific | 2016 |
| JDB Line Limited | Professional & scientific | 2013 |
| JDC (Dorset) Limited | Construction | 2024 |
| JDC IT Services Ltd | Information & communication | 2014 |
| Jdcamperworx Limited | Wholesale & retail | 2020 |
| Jdemand Limited | Administrative & support | 2025 |
| JE Consulting Ltd | Information & communication | 2025 |
| JEB Ventures Ltd | Construction | 2021 |
| JEM Carpets Direct Ltd | Wholesale & retail | 2019 |
| JEM Home Improvements Ltd | Construction | 2025 |
| JEM Systems Limited | Administrative & support | 2023 |
| Jemfx Limited | Financial services | 2018 |
| Jencobond Properties Limited | Households | 1982 |
| Jenkins & Sons Restaurant Limited | Hospitality | 2013 |
| Jenkins Marine Holdings Limited | Financial services | 2016 |
| Jenkins Marine Ltd. | Construction | 1988 |
| Jeremiasz Ltd | Manufacturing | 2018 |
| Jeremy Bragg Surveying + Projects Ltd | Construction | 2013 |
| JERRY077 Limited | Wholesale & retail | 2025 |
| Jervis Site Services Limited | Administrative & support | 2015 |
| Jessopp Bros. (1984) Limited | Construction | 1984 |
| Jessopp Brothers(Bournemouth)Limited | Real estate | 1957 |
| Jess’ Hypnotherapy & Health Ltd | Health & social care | 2025 |
| Jestal Limited | Transport & logistics | 2020 |
| Jesty Limited | Wholesale & retail | 2015 |
| JET International Ltd | Wholesale & retail | 2024 |
| Jetpressurecleaning Ltd | Administrative & support | 2025 |
| Jetseahub Ltd | Manufacturing | 2021 |
| Jetski Safaris Limited | Arts & recreation | 1996 |
| Jettpack Customs Ltd | Wholesale & retail | 2026 |
| Jevi Consulting Ltd | Professional & scientific | 2015 |
| JF Surveys Ltd | Construction | 2026 |
| JFK Property Investment Ltd | Real estate | 2025 |
| JFS PAT Ltd | Manufacturing | 2023 |
| JG - Electrical & Marine Services Ltd | Construction | 2018 |
| JGB Dimensions Ltd | Construction | 2025 |
| JGT Care Homes Limited | Administrative & support | 2012 |
| JGT Electrical Group Limited | Manufacturing | 2015 |
| JH Engineering Consultancy Limited | Professional & scientific | 2019 |
| JH Racing Ltd | Arts & recreation | 2021 |
| JH Taylor Funerals Ltd | Other services | 2019 |
| JHA Law Limited | Professional & scientific | 2023 |
| Jheluxè Limited | Other services | 2022 |
| Jiajia Oriental Food Ltd | Wholesale & retail | 2012 |
| Jigsaw Compliance Services Ltd | Professional & scientific | 2010 |
| Jigsaw Specialist Recruitment Limited | Other services | 2016 |
| JIM Builds Ltd | Professional & scientific | 2022 |
| JIN Catering Ltd | Hospitality | 2019 |
| JIN YUN LAI Ltd | Hospitality | 2026 |
| Jive Marketing Solutions Ltd | Professional & scientific | 2018 |
| Jixip Ltd | Wholesale & retail | 2020 |
| JJ Devon Limited | Education | 2021 |
| JJ Tech Holdings Ltd | Information & communication | 2019 |
| JJ20 Properties Ltd | Real estate | 2024 |
| Jjbac Medical Limited | Health & social care | 2013 |
| JJC Financial Planning Limited | Financial services | 2005 |
| JJC Properties (Surrey) Ltd | Real estate | 2024 |
| Jjda Limited | Other services | 2025 |
| JJE Wealth Limited | Professional & scientific | 2020 |
| JJH Property Management Ltd | Real estate | 2026 |
| JJS CPH Limited | Real estate | 2020 |
| JJS Hold Trading Limited | Professional & scientific | 2020 |
| JJS RPH Limited | Real estate | 2024 |
| JK Consulting, Biuro Podrozy Best Holidays Jaroslaw Kilianek Ltd | Professional & scientific | 2018 |
| JK Dorset Limited | Professional & scientific | 2026 |