| James Oliver Building Services Ltd | Construction | 2022 |
| James S Williams Ltd | Professional & scientific | 2017 |
| James Troop Estates Ltd | Construction | 2011 |
| Jameson Park Ltd | Real estate | 2026 |
| Jammin Design Ltd | Professional & scientific | 2022 |
| JAN Kennedy Training Limited | Professional & scientific | 2019 |
| JAN Molby Sports Media Limited | Information & communication | 2005 |
| JAN Rich Bookkeeping Limited | Professional & scientific | 2025 |
| Janet Thelwall Ltd | Health & social care | 2024 |
| JAO Commercial Limited | Administrative & support | 2018 |
| Jarilo (UK) Limited | Information & communication | 2013 |
| Jarilo Hosting Ltd | Information & communication | 2022 |
| Jarmac Limited | Manufacturing | 1974 |
| Jason Caine Smith Ltd | Other services | 2009 |
| Javid Global Limited | Hospitality | 2025 |
| Jaxson Property Group Ltd | Real estate | 2025 |
| Jay's Bistro Limited | Hospitality | 2018 |
| JAY2E Ltd | Wholesale & retail | 2021 |
| Jaydee Aquatics & Pets Ltd | Wholesale & retail | 2025 |
| Jaydee Aquatics Ltd | Wholesale & retail | 2019 |
| Jays Gymnastics Limited | Arts & recreation | 2019 |
| Jaytee PM Limited | Real estate | 2025 |
| Jazmin Sawyers Limited | Arts & recreation | 2017 |
| JB Assessment Services Limited | Professional & scientific | 2018 |
| JB Properties (Merseyside) Ltd | Real estate | 2025 |
| JB Wellness Dynamics Ltd | Health & social care | 2019 |
| JBP Optical Limited | Administrative & support | 2019 |
| JC Therapy & Case Management Services Ltd | Health & social care | 2021 |
| JC Wellbeing Support Ltd | Health & social care | 2021 |
| JCL Data Labs Ltd | Information & communication | 2019 |
| JCR Protective Solutions Ltd | Professional & scientific | 2021 |
| JCT Property Services Limited | Construction | 2003 |
| JCY Education & Training Limited | Education | 2017 |
| JDB Commercial Consultants Ltd | Education | 2023 |
| JDJ Syndicate Ltd | Wholesale & retail | 2026 |
| JDK Branded Ltd | Wholesale & retail | 2026 |
| JDM Surveying Limited | Administrative & support | 2014 |
| Jefferson O'Connor Ltd | Administrative & support | 2008 |
| Jegliving Ltd | Real estate | 2020 |
| Jejo Rights Limited | Administrative & support | 2025 |
| JEM Holdings Ltd | Professional & scientific | 2026 |
| JEM Joinery (NW) Ltd | Manufacturing | 2016 |
| JEM Trading NW Limited | Wholesale & retail | 2025 |
| JEN RVN Limited | Professional & scientific | 2025 |
| JEN Shaw @ Perseverance Counselling Services Ltd | Health & social care | 2023 |
| Jenard Properties Limited | Construction | 2006 |
| Jenard Ystalyfera Limited | Construction | 2008 |
| Jenny Moran Digital Ltd | Professional & scientific | 2025 |
| Jenz Salon Limited | Other services | 2016 |
| Jeppesen Consulting Limited | Administrative & support | 2005 |
| Jerbourg Limited | Administrative & support | 2023 |
| Jerk & Spice Limited | Hospitality | 2025 |
| Jerry Quayle & Associates Ltd | Professional & scientific | 2019 |
| Jervis Real Estates Ltd | Real estate | 2025 |
| Jessica Barclay Ltd | Other services | 2018 |
| Jessica Garside Ltd | Health & social care | 2022 |
| Jetset Medics Ltd | Public administration | 2019 |
| Jett Payroll Services Limited | Professional & scientific | 2024 |
| Jetw Limited | Wholesale & retail | 2024 |
| Jevdec Ltd | Real estate | 2024 |
| JF Clothing Ltd | Wholesale & retail | 2018 |
| JFC Safety & Access Limited | Health & social care | 2015 |
| Jfew Ltd | Health & social care | 2023 |
| JG Drafts Ltd | Professional & scientific | 2024 |
| JG Facility Management Limited | Real estate | 2017 |
| JGN Catering Ltd | Hospitality | 2025 |
| JHCARE24 Ltd | Wholesale & retail | 2016 |
| Jhgs Rigging Ltd | Mining & quarrying | 2022 |
| JHK Fire Safety Ltd | Public administration | 2022 |
| Jhmurphy Properties Limited | Real estate | 2020 |
| JHP Assist Ltd | Administrative & support | 2024 |
| Jibe by Period Reality Ltd | Education | 2021 |
| Jienco Ltd | Manufacturing | 2010 |
| JIM Vickerage Mortgage Services Ltd | Financial services | 2015 |
| Jinsoku UK Limited | Wholesale & retail | 2023 |
| JJF Capital Ltd | Financial services | 2025 |
| JJF Health & Education Services Ltd | Education | 2015 |
| JJS Property & Investments Ltd | Real estate | 2026 |
| JK Financial Services Limited | Administrative & support | 2013 |
| JK Property Renovation Ltd | Construction | 2022 |
| JK Solutions Ltd | Professional & scientific | 2018 |
| JK Sports Finance Limited | Professional & scientific | 2023 |
| JK Tiling Ltd. | Construction | 2025 |
| Jkam Holdings Limited | Financial services | 2019 |
| Jkam Properties Limited | Real estate | 2026 |
| JKD Education Ltd | Education | 2018 |
| JKO Medical Service Ltd | Health & social care | 2025 |
| JKR Security Ltd | Administrative & support | 2015 |
| JL Build & Construction Ltd | Construction | 2019 |
| Jlay Limited | Transport & logistics | 2020 |
| JLB Entertainment Limited | Education | 2016 |
| Jlbs Plumbing & Heating Limited | Construction | 2025 |
| JLG Properties Limited | Real estate | 2019 |
| Jlohcreative Ltd | Professional & scientific | 2021 |
| JLR Construction (NW) Limited | Construction | 2014 |
| JLS Warehousing Ltd | Real estate | 2021 |
| JM Art & Design Ltd | Administrative & support | 2016 |
| JM Plumbing and Heating (Wirral) Ltd | Other services | 2022 |
| JMD Global Stones Private Limited | Administrative & support | 2020 |
| JMD Housing Solutions Ltd | Real estate | 2022 |