| JM Bookeeping Ltd | Professional & scientific | 2026 |
| JM Elevate Ltd | Professional & scientific | 2026 |
| JM Laws Limited | Transport & logistics | 2003 |
| JMB Health Care Services Ltd | Health & social care | 2023 |
| JMF Allstars Ltd | Administrative & support | 2025 |
| Jmuk Private Ltd | Health & social care | 2017 |
| Jnana Tech Private Limited | Information & communication | 2019 |
| Joal Ventures Limited | Arts & recreation | 2021 |
| Joanne LEE Philpot Limited | Health & social care | 2021 |
| Jocube Limited | Construction | 2025 |
| JOE Dawes Photography Ltd | Professional & scientific | 2021 |
| JOE Digital Solutions Ltd | Information & communication | 2015 |
| JOE Scanlon Limited | Construction | 2025 |
| Joel Woolf Sounds Ltd | Information & communication | 2026 |
| Jofintec Consulting Limited | Financial services | 2015 |
| John a RAY & Associates Limited | Transport & logistics | 2013 |
| John Building Ltd | Construction | 2014 |
| John Ilhan Properties Limited | Real estate | 2025 |
| John Schofield Limited | Professional & scientific | 2012 |
| Johnson Design and Development Limited | Construction | 2010 |
| Johnsons Drone Surveying Ltd | Construction | 2025 |
| Joined Walls Ltd | Real estate | 2024 |
| Jojo Ventures Ltd | Administrative & support | 2024 |
| Jollof &Co Limited | Hospitality | 2024 |
| JOM Ventures Ltd | Manufacturing | 2020 |
| Jonade Services Limited | Professional & scientific | 2019 |
| Jonathan Lawrence Harris Limited | Professional & scientific | 2012 |
| Jonathan Vincent Properties Limited | Real estate | 2019 |
| Jonwelshproperty Limited | Real estate | 2019 |
| Joppa Properties Limited | Real estate | 2002 |
| JP Pharmacy Limited | Wholesale & retail | 2023 |
| Jparkoo Ltd | Information & communication | 2026 |
| JPD Developments Limited | Construction | 2024 |
| JPD Facilities Ltd | Administrative & support | 2022 |
| JPL Engineering and Site Repairs Limited | Professional & scientific | 2022 |
| Jprosoft Ltd | Information & communication | 2023 |
| JR Landscaping Ltd | Administrative & support | 2020 |
| JR London Consultancy Ltd | Professional & scientific | 2024 |
| JR Ollie's Kebab Ltd | Hospitality | 2022 |
| Jrmm Limited | Real estate | 2024 |
| JRMM2 Limited | Real estate | 2025 |
| JRMM3 Limited | Real estate | 2025 |
| JRMM4 Limited | Real estate | 2025 |
| JRMM5 Limited | Real estate | 2025 |
| JRMM6 Limited | Real estate | 2025 |
| JRMM7 Limited | Real estate | 2025 |
| JRMM8 Limited | Real estate | 2025 |
| JRMM9 Limited | Real estate | 2025 |
| JRW3 Ltd | Administrative & support | 2016 |
| JS Connexion Ltd | Professional & scientific | 2025 |
| JS Homes & Lettings Limited | Professional & scientific | 2017 |
| JSA Leisure Limited | Construction | 1997 |
| Jsh&L Holdings Limited | Financial services | 2022 |
| JSK Tech Consultancy Ltd | Information & communication | 2025 |
| JSM South Limited | Construction | 2024 |
| JSM Specialist Solutions Limited | Construction | 2024 |
| JSP Services (London) Ltd | Transport & logistics | 2017 |
| JTC Consultancy Services Ltd | Professional & scientific | 2021 |
| JTL | Education | 2000 |
| JTS Foods Ltd | Hospitality | 2025 |
| Judy's Kitchen Ltd | Hospitality | 2025 |
| Juju Tea Ltd | Wholesale & retail | 2025 |
| Jules Daily Ltd | Information & communication | 2026 |
| Junction 9 Consulting Limited | Professional & scientific | 2015 |
| Juniper Technology Limited | Administrative & support | 2015 |
| Jupiter Resources Limited | Information & communication | 2004 |
| Jureem Properties Ltd | Households | 2025 |
| Jusco Investments Ltd | Real estate | 2020 |
| Just Drainage Services Limited | Water & waste | 2021 |
| Just One More Thing Ltd | Administrative & support | 2009 |
| Just Simple Brockley Cross Ltd | Construction | 2022 |
| Just Simple Geoffrey RD Ltd | Construction | 2023 |
| Just Simple Homes Limited | Construction | 2020 |
| Just Simple Lambeth Ltd | Construction | 2021 |
| Just Simple Lettings Limited | Real estate | 2020 |
| Just Simple Lettings SB Ltd | Real estate | 2021 |
| Just Simple Sidcup Ltd | Real estate | 2022 |
| Just Start Limited | Information & communication | 2025 |
| Just the Tipple Ltd | Hospitality | 2019 |
| Just to SAY Gifting Ltd | Wholesale & retail | 2024 |
| Justjewelsonline Limited | Wholesale & retail | 2022 |
| Juvon Limited | Professional & scientific | 2020 |
| Jv&M Limited | Administrative & support | 2012 |
| JVS Investments Limited | Real estate | 2019 |
| JW Heating Limited | Manufacturing | 2017 |
| JW Maintenance Solutions Ltd | Construction | 2018 |
| JW Payments Ltd | Information & communication | 2025 |
| JW Roofing Contractors Limited | Construction | 2014 |
| JWL Heating Limited | Construction | 2025 |
| JWM Financial Limited | Financial services | 2026 |
| Jwm-Es Ltd | Construction | 2025 |
| JWP Investments Limited | Financial services | 2017 |
| JXM Limited | Hospitality | 2022 |
| JY Autocentres Limited | Wholesale & retail | 2025 |
| Jycn Ltd | Wholesale & retail | 2024 |
| JZ Ltd | Wholesale & retail | 2023 |
| JZ Your Home Ltd | Construction | 2025 |
| Jéba Baiga Ltd | Wholesale & retail | 2024 |
| K & K Property Holdings Ltd | Real estate | 2017 |
| K a Creative Ltd | Professional & scientific | 2024 |