| Jacks River Productions Limited | Information & communication | 2024 |
| Jacks Takeaway Limited | Hospitality | 2022 |
| Jackson Accounts Limited | Professional & scientific | 2013 |
| Jackson Flemming Ltd | Financial services | 2024 |
| Jacksonjonesrail Limited | Construction | 2017 |
| Jacob and Joseph UK Ltd | Other services | 2021 |
| Jacob Miller Ltd | Professional & scientific | 2018 |
| Jacob Wells Rehab Ltd | Administrative & support | 2020 |
| Jacobson Property Group Ltd | Real estate | 1954 |
| Jacs Lighting Ltd | Wholesale & retail | 2020 |
| Jacs Supplies Ltd | Wholesale & retail | 2024 |
| Jade Moon Media Ltd | Education | 2016 |
| Jade Properties Limited | Real estate | 2014 |
| Jafa (Pipss) Ltd | Extraterritorial | 2002 |
| Jafa North-East UK Ltd | Extraterritorial | 2003 |
| Jaffer Bhai's Restaurant and Catering Kitchen Ltd | Hospitality | 2022 |
| JAG Acquisitions Limited | Financial services | 2025 |
| JAG Logistics Ltd | Transport & logistics | 2026 |
| JAG Medical Aesthetics Limited | Health & social care | 2023 |
| JAG Property Group Ltd | Real estate | 2025 |
| Jaga Joinery and Building Limited | Construction | 2023 |
| Jaganas Courier Ltd | Transport & logistics | 2025 |
| Jago Properties Ltd | Real estate | 2008 |
| Jagoda Style Ltd | Wholesale & retail | 2021 |
| Jagusz Optical Limited | Financial services | 2026 |
| Jaid Construction Ltd | Construction | 2026 |
| Jaidpur Traders Ltd | Wholesale & retail | 2024 |
| Jaipa Limited | Information & communication | 2014 |
| JAJ Driving Services (Lancashire) Limited | Transport & logistics | 2020 |
| Jajacare Ltd | Health & social care | 2014 |
| Jakdaw Limited | Manufacturing | 2019 |
| Jake Brennan Productions Ltd | Information & communication | 2021 |
| Jake Hughes Services Limited | Transport & logistics | 2018 |
| Jake Mears Cars Limited | Wholesale & retail | 2025 |
| Jakky Care Group Limited | Public administration | 2020 |
| Jakob Ltd | Transport & logistics | 2025 |
| Jaks Hair Boutique Limited | Other services | 2013 |
| JAL 1984 Holdings Ltd | Financial services | 2023 |
| JAM + Post Ltd | Information & communication | 2023 |
| Jamal Al-Rooh Ltd | Wholesale & retail | 2026 |
| Jamal Travel and Tours Ltd | Administrative & support | 2018 |
| Jambuzi Ltd | Professional & scientific | 2019 |
| Jameel Builder Ltd | Construction | 2025 |
| Jameel Stuart Cricket Academy Ltd | Arts & recreation | 2025 |
| James & James Medical Ltd | Education | 2025 |
| James Booth(Bolton),Limited | Transport & logistics | 1928 |
| James Brown ACP Medicolegal Ltd | Health & social care | 2026 |
| James Clothing Club (Jcclub) Ltd. | Wholesale & retail | 2017 |
| James Cooper Contracting Limited | Information & communication | 2022 |
| James D Butterworth Limited | Transport & logistics | 2013 |
| James D Philbin Holdings Limited | Professional & scientific | 2006 |
| James D. Philbin Limited | Wholesale & retail | 1975 |
| James Farrell-Roberts Hairdressing Ltd | Other services | 2023 |
| James Gallagher Limited | Construction | 2006 |
| James Gosai Ltd | Real estate | 2021 |
| James Greeley & Sons Ltd | Wholesale & retail | 2017 |
| James Helgason Limited | Wholesale & retail | 1984 |
| James Industrial Limited | Administrative & support | 1986 |
| James Lever 1856 Ltd | Manufacturing | 2011 |
| James Luke REC Ltd | Transport & logistics | 2023 |
| James Lynch Ltd | Information & communication | 2014 |
| James Officer Restaurant Limited | Hospitality | 2018 |
| James Properties Holdings Limited | Real estate | 2023 |
| James Robertshaw & SON (1954) Limited | Manufacturing | 1954 |
| James Stone Masonary Limited | Manufacturing | 2007 |
| James Taylor & Co Hairdressing Limited | Other services | 2018 |
| Jamesqs Ltd | Professional & scientific | 2008 |
| Jamesy's Transport & Recovery Limited | Transport & logistics | 2022 |
| Jamiat Ulama-I-Hind UK Ltd | Education | 2008 |
| Jamie Davies Limited | Transport & logistics | 2025 |
| Jamie Mears Cars Ltd | Wholesale & retail | 2024 |
| Jamie Ventures Ltd | Hospitality | 2025 |
| Jamii Souk UK Ltd | Wholesale & retail | 2025 |
| Jamlx Ltd | Construction | 2026 |
| JAN & Sons Group Ltd | Hospitality | 2026 |
| JAN Care Services Ltd | Administrative & support | 2022 |
| Janat Textile Limited | Wholesale & retail | 2022 |
| Jand Technical Services Ltd | Information & communication | 2014 |
| Jandanwala Ltd | Wholesale & retail | 2026 |
| Jandico Ltd | Wholesale & retail | 2015 |
| Jane Coyne Consultancy Ltd | Professional & scientific | 2026 |
| Jane Weston Mortgages & Protection Ltd | Financial services | 2017 |
| Jangro Limited | Other services | 1995 |
| Jangro Logistics Limited | Administrative & support | 2014 |
| Jangro Network Limited | Administrative & support | 1999 |
| Janto Global Commerce & Logistics Ltd | Transport & logistics | 2026 |
| JAP Car Sales Ltd | Wholesale & retail | 2024 |
| JAP Motors (Bolton) Limited | Wholesale & retail | 2026 |
| JAP Parts Europe Limited | Wholesale & retail | 2014 |
| JAR Cabling Services Limited | Construction | 2003 |
| Jarern Street Food Limited | Hospitality | 2019 |
| Jarv Consulting Ltd | Professional & scientific | 2016 |
| Jarv Properties Limited | Real estate | 2021 |
| Jarvis - Ryder Ltd | Professional & scientific | 2024 |
| Jarvis Spencer Jewellery Limited | Wholesale & retail | 2016 |
| Jarvisco Limited | Information & communication | 2007 |
| Jascon International Ltd | Wholesale & retail | 2025 |
| Jasdan Investments Ltd | Administrative & support | 2020 |
| Jase of Spades Limited | Information & communication | 2019 |
| Jasgrow Ltd | Financial services | 2023 |