| Janixen Limited | Manufacturing | 2023 |
| Jannat by IK Collection Ltd | Wholesale & retail | 2020 |
| Janoss Nails Limited | Other services | 2022 |
| Janson Computers Limited | Information & communication | 1987 |
| Janua Hortorum Limited | Information & communication | 2001 |
| Janua Limited | Professional & scientific | 2014 |
| Janya Medical Services Ltd | Health & social care | 2022 |
| Janya Property Management Limited | Real estate | 2023 |
| Japan Partners UK Ltd | Wholesale & retail | 2019 |
| Japan Tokyo Ltd | Wholesale & retail | 2025 |
| Japri Limited | Real estate | 2022 |
| JAR Haulage Ltd | Transport & logistics | 2018 |
| Jarca UK Properties Limited | Real estate | 2026 |
| Jardin DE Roses Limited | Real estate | 2023 |
| Jarlon Limited | Professional & scientific | 2013 |
| Jaro Properties Ltd | Real estate | 2023 |
| Jaro Security Services Limited | Administrative & support | 2026 |
| Jarose Interiors Limited | Manufacturing | 2013 |
| Jarose Shopfitters Limited | Construction | 2016 |
| Jarred PIN Limited | Professional & scientific | 2003 |
| Jarrow Innovations Ltd | Manufacturing | 2014 |
| Jarvis & Partners Ltd | Professional & scientific | 2024 |
| JAS Consultancy (Leeds) Ltd | Financial services | 2019 |
| JAS Expert Witness Services Ltd | Health & social care | 2018 |
| JAS Pharma Ltd | Wholesale & retail | 2019 |
| JAS Speech Neuro Limited | Health & social care | 2024 |
| Jase Supplies Limited | Other services | 2011 |
| Jasi &J Limited | Administrative & support | 2024 |
| Jaskaran S DEU Properties Limited | Real estate | 2016 |
| Jasko Paint Process Engineering Limited | Administrative & support | 2013 |
| Jasmin Valencia & Associates Limited | Health & social care | 2016 |
| Jasmine Baran Ltd | Administrative & support | 2025 |
| Jasmine Thai Massage Limited | Health & social care | 2022 |
| Jasmine's Flowers Limited | Wholesale & retail | 2023 |
| Jason Lloyd Apps Limited | Information & communication | 2022 |
| Jason Stead Building Contractors Limited | Construction | 2011 |
| Jasons of Kippax Limited | Other services | 2003 |
| Jaspal Ltd | Wholesale & retail | 2025 |
| Jastr Limited | Administrative & support | 2018 |
| Jaszi Education LLP | | 2021 |
| JAT Care Ltd | Health & social care | 2016 |
| JAT Perioperative Services Ltd | Health & social care | 2026 |
| JAV Homes Ltd | Real estate | 2019 |
| Javaid Iqbal (UK) Limited | Real estate | 2007 |
| Javaitas Ltd | Hospitality | 2024 |
| Javaldsdriver 01 Limited | Transport & logistics | 2016 |
| Javan Ltd | Real estate | 2019 |
| Javelin Marketing Ltd | Professional & scientific | 2023 |
| Javid Ace Ltd | Arts & recreation | 2023 |
| JAW Holdings Limited | Information & communication | 2015 |
| JAW Services (Halifax) Ltd | Financial services | 2017 |
| Jawara 22 Ltd | Wholesale & retail | 2026 |
| JAX Barbershop Ltd | Other services | 2018 |
| Jaxdoodle Ltd | Real estate | 2025 |
| Jaxsons Properties Ltd | Real estate | 2025 |
| Jaxy Properties Ltd | Real estate | 2026 |
| JAY & JAY Group Ltd | Wholesale & retail | 2019 |
| JAY Bagri Limited | Real estate | 2019 |
| JAY Build and Roof Ltd | Construction | 2024 |
| JAY D Autos Ltd | Wholesale & retail | 2019 |
| Jay's Desserts Ltd | Hospitality | 2021 |
| JAY2KIM Limited | Wholesale & retail | 2025 |
| Jayakumar Healthcare Ltd | Health & social care | 2021 |
| Jayarjun S DEU Properties Limited | Real estate | 2016 |
| Jayati Holdings Ltd | Real estate | 2025 |
| Jaycee Furniture (Brighton) Limited | Professional & scientific | 1947 |
| Jaydot Ventures Ltd | Professional & scientific | 2025 |
| Jaygo Services Limited | Professional & scientific | 2016 |
| Jayne Leedham Ltd | Other services | 2013 |
| Jayne Stevens Limited | Other services | 2010 |
| Jayraj R Limited | Wholesale & retail | 2025 |
| Jayrima Care Limited | Health & social care | 2016 |
| Jayrock Joinery Ltd | Construction | 2018 |
| Jays Roofing & Property Maintenance Ltd | Construction | 2025 |
| Jaytex Ltd | Wholesale & retail | 2020 |
| Jayvee Catering Limited | Hospitality | 2024 |
| JAZ Holdings Limited | Other services | 2025 |
| JAZ Singh Granary Express Ltd | Wholesale & retail | 2017 |
| JAZ Technologies Ltd | Information & communication | 2024 |
| Jaz&Sons Prestige Cars Ltd | Wholesale & retail | 2025 |
| Jazreal Homes Ltd | Real estate | 2024 |
| Jazzy Solutions Limited | Professional & scientific | 2024 |
| Jazzyindian Limited | Hospitality | 2023 |
| Ja’Fleur Ltd | Wholesale & retail | 2025 |
| JB & TB Investments Ltd | Financial services | 2016 |
| JB 23 Ltd | Construction | 2023 |
| JB Andrews Executive Search Group Holdings Limited | Administrative & support | 2024 |
| JB Andrews Executive Search Limited | Administrative & support | 2018 |
| JB Building Contractors (Leeds) Limited | Construction | 2016 |
| JB Capital Properties Limited | Real estate | 2024 |
| JB Colbert Capital Ltd | Administrative & support | 2021 |
| JB Construction Landscaping & Groundworks Ltd | Construction | 2025 |
| JB Decor Services Ltd | Construction | 2017 |
| JB Flight Ltd | Education | 2025 |
| JB Imaging Limited | Arts & recreation | 2024 |
| JB Joinery Building Services Ltd | Manufacturing | 2019 |
| JB Joinery Leeds Ltd | Construction | 2026 |
| JB Nail & Beauty Supply Ltd | Other services | 2020 |
| JB Network Services Ltd | Information & communication | 2016 |
| JB PAT Testing Ltd | Manufacturing | 2022 |