| Info Launch Limited | Professional & scientific | 2025 |
| Infonetica Ltd | Information & communication | 2002 |
| Ingenivm Group Ltd | Administrative & support | 2024 |
| Inspired Expertise Ltd | Wholesale & retail | 2007 |
| Inspired Home Solutions Ltd | Construction | 2024 |
| Integer Partnership Limited | Professional & scientific | 2001 |
| Integer Planning & Development Limited | Construction | 2018 |
| Integrated Energy Consulting Limited | Professional & scientific | 2022 |
| Integrifood Solutions Ltd | Administrative & support | 2024 |
| Integris Estates Ltd | Real estate | 2002 |
| Intercontinental Biomass Brokers Ltd | Financial services | 2016 |
| Interim and Consulting Solutions With Paice Ltd | Professional & scientific | 2011 |
| International Advertising Association United Kingdomchapter Limited | Professional & scientific | 1962 |
| International Institute of Communications | Administrative & support | 1970 |
| International Public Relations Association Limited | Administrative & support | 1999 |
| Interview Coach Ltd | Administrative & support | 2022 |
| Intuvis Ltd | Professional & scientific | 2026 |
| Invetech Limited | Construction | 2004 |
| Invit Ltd | Administrative & support | 2016 |
| Iridium World Limited | Professional & scientific | 2026 |
| Irise Career and Life Coaching Ltd | Other services | 2024 |
| Isja Consultancy Limited | Professional & scientific | 2016 |
| Isolid Limited | Information & communication | 2013 |
| Italian Food Connection Limited | Wholesale & retail | 2014 |
| IVY Place Design Ltd | Wholesale & retail | 2022 |
| IVY Place Holdings Ltd | Real estate | 2025 |
| IVY Place Property Ltd | Real estate | 2020 |
| J Bridges Roofing Limited | Construction | 2006 |
| J D K Trading Ltd | Wholesale & retail | 2018 |
| J Hill Performance Driving Ltd | Professional & scientific | 2025 |
| J Kriegel & Associates Ltd | Professional & scientific | 2024 |
| J Thomas Building Services Ltd | Construction | 2017 |
| J Valler & Sons Limited | Construction | 2025 |
| J Vineall Haulage Limited | Construction | 2005 |
| J-L Partnership Limited | Information & communication | 2009 |
| Jade Davies Events Ltd | Administrative & support | 2025 |
| James Blunt Limited | Administrative & support | 2001 |
| James Holland-Hibbert Limited | Administrative & support | 2001 |
| James Pendleton Real Estate Ltd | Real estate | 2026 |
| Jamie Lloyd Limited | Arts & recreation | 2023 |
| Janner Multi Media Limited | Administrative & support | 2025 |
| Janoa Ltd | Extraterritorial | 2013 |
| Jarv Holdings Ltd | Professional & scientific | 2026 |
| Jasto Ventures Ltd | Professional & scientific | 2024 |
| JCK Karate Limited | Education | 2023 |
| JCK Sports Limited | Wholesale & retail | 2023 |
| Jdfp Limited | Real estate | 2025 |
| Jefed Consulting Limited | Professional & scientific | 2010 |
| Jeffco AM Ltd | Professional & scientific | 2025 |
| Jeffco Limited | Professional & scientific | 2021 |
| Jenlockprops Ltd | Information & communication | 2018 |
| Jenta Ltd | Hospitality | 2019 |
| JGW Media Ltd. | Administrative & support | 2016 |
| Jhambleton Property Limited | Real estate | 2024 |
| JJB Advisory Limited | Real estate | 2017 |
| JJO Harris Limited | Other services | 2025 |
| JK Chinese Healthcare Ltd | Health & social care | 2012 |
| JKT Management Ltd | Professional & scientific | 2023 |
| Jlvest Ltd | Other services | 2021 |
| Jobrelay Ltd | Information & communication | 2024 |
| John Charlick Foods Limited | Hospitality | 2002 |
| JON Sturgeon Consultancy Ltd | Professional & scientific | 2020 |
| JR Photography Ltd | Professional & scientific | 2016 |
| JRS Stone Consultants Ltd | Manufacturing | 2015 |
| JRS Stone International Ltd | Manufacturing | 2021 |
| JRS UK Property Ltd | Real estate | 2026 |
| JSC MX Group Ltd | Information & communication | 2022 |
| Jskr Pharma Limited | Wholesale & retail | 2010 |
| JSS Developments Limited | Real estate | 2020 |
| JSS Partners Limited | Real estate | 2025 |
| JTD Connections Limited | Professional & scientific | 2013 |
| Jteor Consultants Ltd | Professional & scientific | 2017 |
| Julian Rowe-Jones Limited | Health & social care | 2003 |
| Julie Sianne Theatre Arts Ltd | Arts & recreation | 2015 |
| Jungleland Limited | Information & communication | 1999 |
| Juno Moneta Ltd | Financial services | 2025 |
| Jwei International Limited | Wholesale & retail | 2017 |
| JZ Designs Limited | Arts & recreation | 2015 |
| K N Mathias Events Limited | Administrative & support | 2009 |
| K Watts Construction Limited | Construction | 2002 |
| K&K OFF Licence Ltd | Wholesale & retail | 2022 |
| Kafi Folk Ltd | Wholesale & retail | 2023 |
| Kaizen Engineering Limited | Professional & scientific | 2024 |
| Kaizen IQ Ltd | Information & communication | 2025 |
| Kaleidoscope Management Ltd | Wholesale & retail | 2013 |
| Kaleidoscope Social Ltd | Professional & scientific | 2022 |
| Kalkeus Limited | Professional & scientific | 2008 |
| Kalos Communications Ltd | Professional & scientific | 2022 |
| Kastilion Ltd | Other services | 2017 |
| KAT Investments (Surrey) Limited | Construction | 2014 |
| Katorox (NO.1) Limited | Real estate | 2024 |
| Katorox Limited | Professional & scientific | 2013 |
| Kavanagh Retailing (UK) Limited | Wholesale & retail | 2005 |
| Kavanaghs Belsize Holdings Ltd | Financial services | 2017 |
| Kavanaghs Belsize Ltd | Wholesale & retail | 2005 |
| Kbal Property Ltd | Real estate | 2024 |
| Kearada Limited | Information & communication | 2021 |
| Keith Todd Limited | Professional & scientific | 2004 |
| Keltbray (BE) Holdings Limited | Financial services | 2023 |
| Keltbray Built Environment Limited | Construction | 2020 |