| JMW Consultancy Limited | Professional & scientific | 2012 |
| JNK Properties Ltd | Real estate | 2020 |
| JNK Solutions Ltd | Information & communication | 2015 |
| Johal Law Limited | Professional & scientific | 2021 |
| John Barford Limited | Professional & scientific | 2015 |
| John Snow Food and Wine Limited | Wholesale & retail | 2020 |
| John Walker Gardeners Limited | Other services | 2003 |
| John Waugh Music Limited | Arts & recreation | 2019 |
| Johnny G Tours Ltd | Professional & scientific | 2026 |
| Johnson Cloud Consultancy Ltd | Information & communication | 2023 |
| Jolk Hospitality Services Limited | Administrative & support | 2024 |
| Jollyhealth Ltd | Health & social care | 2021 |
| JON Avol & Associates Limited | Real estate | 2012 |
| Jooma Properties Limited | Real estate | 2017 |
| Jopebarn Ltd | Real estate | 2024 |
| Jords Enterprises Limited | Arts & recreation | 2021 |
| Joshnik Limited | Health & social care | 2026 |
| Jotangia Consultancy Limited | Professional & scientific | 2010 |
| Jothiraj Anaesthesia Ltd | Health & social care | 2026 |
| Joud Home Maintenance Ltd | Construction | 2026 |
| Joy Foods Limited | Manufacturing | 2001 |
| Joydent Limited | Health & social care | 2023 |
| Joyline Fashions (UK) Limited | Wholesale & retail | 2022 |
| Joyline Holdings Limited | Financial services | 2023 |
| Joyner Properties Ltd | Real estate | 2026 |
| Joyzy Limited | Health & social care | 2015 |
| JP Nivas Properties Limited | Real estate | 2023 |
| JP Property Asset Management Limited | Real estate | 2017 |
| JP Wealth Ltd | Real estate | 2024 |
| JPA Residential Limited | Real estate | 2022 |
| JR & Company (GB) Ltd | Professional & scientific | 2008 |
| JR Athwal Ltd | Real estate | 2024 |
| JR Capital Partners 1 Limited | Real estate | 2023 |
| JR Capital Partners Limited | Real estate | 2022 |
| JR Imaging Limited | Professional & scientific | 2023 |
| JR Property Solutions Limited | Real estate | 2017 |
| JRF Consultancy Ltd | Other services | 2015 |
| JRG Property UK Ltd | Administrative & support | 2024 |
| JRH Pharma Ltd | Information & communication | 2025 |
| JS Property Homes Limited | Real estate | 2016 |
| JS Property Homes Management Limited | Administrative & support | 2017 |
| JSA Information Technology Ltd | Information & communication | 2017 |
| JSC Property Investment Limited | Real estate | 2017 |
| JSD Estates LLP | | 2013 |
| JSK Consultancy Services Limited | Professional & scientific | 2021 |
| JSR Commercial Investments Limited | Real estate | 2022 |
| JSR Financial Services Limited | Financial services | 2018 |
| JSR Properties Investment Limited | Real estate | 2020 |
| JSR Property Investment Limited | Real estate | 2020 |
| JSR Realty Ltd | Real estate | 2019 |
| JSS Corporation Limited | Wholesale & retail | 2023 |
| JSS Holdings Limited | Professional & scientific | 2007 |
| JU Capital Ltd | Real estate | 2025 |
| JU Property Limited | Administrative & support | 2019 |
| JU Real Estate Limited | Real estate | 2018 |
| Jubilee Close 2017 Management Limited | Real estate | 2017 |
| Juice Cube Ltd. | Hospitality | 2013 |
| Jujhar Limited | Real estate | 2020 |
| Juke Music Ltd | Information & communication | 2024 |
| Julie Browne Event Management Limited | Administrative & support | 2000 |
| Jump UP Logistics Limited | Transport & logistics | 2017 |
| Junior and Tiny Tots Limited | Health & social care | 2024 |
| Junk Buddies Ltd | Water & waste | 2025 |
| Jupiter Group Limited | Real estate | 2015 |
| Just Pizza Plus ( Eastcote ) Limited | Hospitality | 2022 |
| Justbe Platform Ltd | Information & communication | 2026 |
| JVL Consultancy Limited | Professional & scientific | 2017 |
| JVM Architecture Ltd | Professional & scientific | 2018 |
| Jwright Consulting Ltd | Administrative & support | 2023 |
| Jyoti Patel Ltd | Health & social care | 2013 |
| Jyoti Varsani Ltd | Health & social care | 2025 |
| K & D Estates Limited | Real estate | 2024 |
| K & E Property Developments Ltd | Construction | 2011 |
| K & S Brook Road Property Limited | Real estate | 2022 |
| K & S Grand Properties Ltd | Real estate | 2019 |
| K 2 Cars Ltd | Transport & logistics | 2008 |
| K a Properties London Ltd | Households | 2021 |
| K Chiropractor Limited | Health & social care | 2024 |
| K Dean Building Services Ltd | Construction | 2021 |
| K J C Electrical Solutions Limited | Construction | 2023 |
| K J Webster & Sons Ltd | Construction | 2014 |
| K Squared Group Limited | Professional & scientific | 2023 |
| K&B London Property Group Ltd | Real estate | 2025 |
| K&Lray Limited | Health & social care | 2024 |
| K'S Bar and Restaurant Ltd | Hospitality | 2016 |
| K-Plex Investments Limited | Real estate | 2019 |
| K-Stone Limited | Construction | 2011 |
| K. K. Shah Investments Limited | Wholesale & retail | 2014 |
| K21 Academy Ltd | Information & communication | 2017 |
| K2KICKBOXING Limited | Arts & recreation | 2020 |
| KAA Partners Ltd | Information & communication | 2023 |
| Kaag Capitals Ltd | Financial services | 2025 |
| Kaag Ventures Limited | Financial services | 2022 |
| Kaar Investments Limited | Real estate | 2025 |
| Kaarvi Ltd | Information & communication | 2014 |
| Kaashmira Ltd | Information & communication | 2019 |
| Kaber Limited | Real estate | 1957 |
| Kabir Umbrella Services Ltd | Information & communication | 2025 |
| Kainotech Limited | Professional & scientific | 2025 |
| Kaleidoscope Transformations Limited | Administrative & support | 2015 |