| Jameson Cooper Limited | Hospitality | 2012 |
| Jamm Consult Limited | Professional & scientific | 2013 |
| Jamtech Solutions (Consulting) Ltd | Professional & scientific | 2025 |
| Jamtech Solutions (Engineering) Ltd | Professional & scientific | 2025 |
| Jamtech Solutions (Professional Services) Ltd | Extraterritorial | 2025 |
| Jamtech Solutions (Surveys) Ltd | Extraterritorial | 2025 |
| Jamtech Solutions (Treatment) Ltd | Extraterritorial | 2025 |
| Jamtech Solutions Ltd | Professional & scientific | 2023 |
| Jane and Mike Partnership Limited | Professional & scientific | 2011 |
| Jangjeet Ltd | Transport & logistics | 2024 |
| Janie Perry Limited | Health & social care | 2022 |
| Janlolalux Ltd | Professional & scientific | 2013 |
| Jaoude Studios Limited | Information & communication | 2010 |
| Jarrott Limited | Real estate | 1981 |
| Jarvis People Investments Ltd | Administrative & support | 2023 |
| Jasbs Ltd | Administrative & support | 2017 |
| Jason Crabtree Psychology Limited | Health & social care | 2022 |
| Jass Investment Ltd | Real estate | 2017 |
| Jathe Elite Ltd | Wholesale & retail | 2025 |
| JAY Food and Wine PVT Ltd | Wholesale & retail | 2025 |
| JAY Properties Enterprise Ltd | Real estate | 2025 |
| JB & MG Consulting Limited | Manufacturing | 1992 |
| JB & MG Holdings Consulting Limited | Extraterritorial | 1999 |
| JB Build (UK) Ltd | Construction | 2014 |
| JBR Decor & Maintenance Ltd | Other services | 2017 |
| JBW Carpentry Ltd. | Construction | 2016 |
| Jcolley & Co Limited | Professional & scientific | 2025 |
| Jcpc Services Limited | Real estate | 2019 |
| JD Decorating Ltd | Construction | 2023 |
| JDC Orthopaedics Limited | Health & social care | 2021 |
| JDR Info System Ltd | Professional & scientific | 2019 |
| Jecoe Ltd | Professional & scientific | 2018 |
| Jeedil Limited | Real estate | 2020 |
| Jefferson Marketing Limited | Administrative & support | 2013 |
| Jehangiri Polo Limited | Agriculture & fishing | 2024 |
| Jenetta Barry Limited | Education | 2016 |
| Jenius IT Ltd | Information & communication | 2015 |
| Jenners Catering Limited | Hospitality | 1995 |
| Jenni Does IT Ltd | Information & communication | 2016 |
| Jenny Enterprise Ltd | Wholesale & retail | 2023 |
| Jenny Spray Coaching Ltd | Professional & scientific | 2021 |
| Jerick Consultants Limited | Professional & scientific | 2013 |
| Jerry CAN Limited | Manufacturing | 2022 |
| JET Roller Services Limited | Manufacturing | 2014 |
| Jetco Ltd | Other services | 2002 |
| Jetstream Consulting Group Limited | Professional & scientific | 2021 |
| Jett Creative Ltd | Professional & scientific | 2025 |
| Jewels Comfort Ltd | Hospitality | 2025 |
| JH Social Work Solutions Ltd | Professional & scientific | 2019 |
| JH Whittaker Property Investment Limited | Real estate | 2019 |
| Jhbh Holding Company Ltd | Financial services | 2023 |
| Jhpi Ltd | Wholesale & retail | 2019 |
| Jig's Lane (Bracknell) M.C. Limited | Households | 1999 |
| JIM Busby Rigging Services Ltd | Information & communication | 2009 |
| JIM Inc. Limited | Professional & scientific | 2024 |
| Jimbao Ltd | Wholesale & retail | 2017 |
| JJS Recruiting Limited | Administrative & support | 2017 |
| Jjsl Consultancy Limited | Information & communication | 2016 |
| JK Executive Coaching Ltd | Professional & scientific | 2025 |
| JK Musicals Ltd | Health & social care | 2023 |
| JK Rent-Wise Solutions Ltd | Real estate | 2025 |
| JK Tech Consultants Ltd | Information & communication | 2018 |
| Jklk Ltd | Wholesale & retail | 2023 |
| JKM Medical Ltd | Health & social care | 2021 |
| JL Financial Management Ltd | Professional & scientific | 2026 |
| JLA Builders Limited | Construction | 2019 |
| Jlfh SEN Support Ltd | Administrative & support | 2017 |
| JLO Technology Ltd | Administrative & support | 2023 |
| JLS2050 Limited | Other services | 2017 |
| JM & Co. Advisory Limited | Professional & scientific | 2026 |
| JM Clark Builders Ltd | Construction | 2026 |
| JM Electrical (Southern) Ltd | Construction | 2020 |
| JM Protection Group Ltd | Administrative & support | 2024 |
| JM Wholesale Limited | Wholesale & retail | 2017 |
| JMC Media Ltd | Professional & scientific | 2018 |
| JMD Marketing Limited | Professional & scientific | 2015 |
| JMF Cleaning Services Ltd | Administrative & support | 2022 |
| JMN Advisory Limited | Professional & scientific | 2025 |
| JMR Surveying Ltd | Professional & scientific | 2026 |
| JNC Solutions Ltd. | Information & communication | 1993 |
| JNH Developments Limited | Real estate | 2019 |
| Joanne Cook Coaching and Consulting Ltd | Other services | 2018 |
| JOB Dunn Ltd | Administrative & support | 2013 |
| JOB Trader Limited | Wholesale & retail | 2015 |
| Jobz Services Limited | Other services | 2016 |
| Jodie Relf Limited | Professional & scientific | 2017 |
| JOE & Sons Property Developments Ltd | Construction | 2020 |
| John Dinham Transport Ltd | Transport & logistics | 2014 |
| John Harrison Limited | Arts & recreation | 2003 |
| John Keogh Design Limited | Professional & scientific | 2016 |
| John Murphy and Company Limited | Construction | 1995 |
| John Power Developments Limited | Other services | 2010 |
| John Trueman Ltd | Information & communication | 2010 |
| Johnstone & Skye Associates Limited | Administrative & support | 2016 |
| Joiner Cummings and Company Limited | Professional & scientific | 1997 |
| Joisos Ltd | Professional & scientific | 2024 |
| Jolleos Ltd | Real estate | 2021 |
| JON Savage Special Effects Limited | Other services | 2003 |
| Jonas Property Ltd | Households | 2024 |
| Jonathan Street Public Relations Limited | Professional & scientific | 2007 |