| Integrated Electrotechnical Solutions Ltd | Construction | 2023 |
| Integrity Divine Properties Ltd | Real estate | 2019 |
| Inter Corp Relocation London Limited | Hospitality | 2016 |
| Interior TEC Limited | Construction | 2012 |
| International Human Rights Committee Limited | Information & communication | 2013 |
| International Petroleum Investment Company Limited | Extraterritorial | 2013 |
| International Trading Solutions Ltd | Wholesale & retail | 2020 |
| Intext Developments Limited | Real estate | 2016 |
| IP Solutions London Ltd | Construction | 2015 |
| IPI Group Ltd | Information & communication | 2025 |
| Ippon Judo London Ltd | Education | 2019 |
| Ippon Judo Ltd | Education | 2019 |
| Iprain Clouds Services Ltd | Information & communication | 2011 |
| IPS Renovation Ltd | Construction | 2011 |
| IQ Tyres Limited | Wholesale & retail | 2021 |
| Iron Aura Labs Limited | Information & communication | 2026 |
| Ironcore Property Services Ltd | Construction | 2026 |
| Ironfoil Limited | Extraterritorial | 1974 |
| Ironman 88 Ltd | Transport & logistics | 2015 |
| Ironpilot Industrial Services Ltd | Manufacturing | 2025 |
| Isa.Bell Productions Limited | Other services | 2023 |
| Isabel Beauty Ltd | Other services | 2016 |
| Isabelka Ltd | Information & communication | 2014 |
| Isaiah Limited | Administrative & support | 2013 |
| Isaphozadav Limited | Health & social care | 2019 |
| ISD Building Ltd | Construction | 2017 |
| Island Salt & Spice Limited | Hospitality | 2025 |
| ISM Shipping Solutions Limited | Professional & scientific | 1998 |
| Ismail Landry Services Ltd | Other services | 2025 |
| Ispa Properties Ltd | Professional & scientific | 1999 |
| IT Services Hub Ltd. | Information & communication | 2018 |
| IT Solutions 4U Ltd | Information & communication | 2019 |
| It's Sports Day Ltd | Wholesale & retail | 2021 |
| Itaga Ltd | Administrative & support | 2026 |
| Itorit Limited | Transport & logistics | 1988 |
| Ivan Home Construction Ltd | Manufacturing | 2025 |
| Ivanette Properties Limited | Construction | 2022 |
| IVN Construct Limited | Construction | 2018 |
| Ivyzz Recruitment Services Limited | Administrative & support | 2025 |
| Iyanaar Ltd | Wholesale & retail | 2024 |
| Izanami Solutions & Logistics Ltd | Transport & logistics | 2019 |
| Izanami Solutions Limited | Other services | 2009 |
| IZT Limited | Wholesale & retail | 2026 |
| J a Ravensbury Ltd | Wholesale & retail | 2025 |
| J C Interiors Surrey Limited | Construction | 2011 |
| J Carroll & Sons Limited | Manufacturing | 2018 |
| J D Z Couriers Ltd | Transport & logistics | 2016 |
| J Hound Treasures Ltd | Wholesale & retail | 2024 |
| J K Boateng Holdings Ltd | Financial services | 2026 |
| J K Boateng Ltd | Information & communication | 2024 |
| J R C Scenic Limited | Professional & scientific | 2012 |
| J Wojtowicz Enterprises Ltd | Real estate | 2014 |
| J&A Gardeners Ltd | Professional & scientific | 2021 |
| J&Jgonzale$ Limited | Health & social care | 2014 |
| J.W.& H.Platt Limited | Extraterritorial | 1937 |
| J11 Enterprise Limited | Wholesale & retail | 2026 |
| JA Emerald Medical Services Limited | Health & social care | 2014 |
| Jaar Consulting Limited | Professional & scientific | 2015 |
| Jaasecured Ltd | Information & communication | 2025 |
| Jack Builders Ltd | Construction | 2018 |
| Jack Mack Ltd | Professional & scientific | 2025 |
| Jackdaw Joinery & Furniture Makers Ltd | Manufacturing | 2010 |
| Jacqueline H Accounting Ltd | Professional & scientific | 2018 |
| Jada Chungi Ltd | Health & social care | 2025 |
| Jaffna Hindu Ladies' College OGA UK | Professional & scientific | 2021 |
| Jaishreekrishna Limited | Wholesale & retail | 2024 |
| James & Co. Property Investments Ltd | Real estate | 2023 |
| Jammat Care Limited | Health & social care | 2023 |
| Jammu Building and Construction Ltd | Construction | 2022 |
| JAN & JAN Holding Limited | Real estate | 2024 |
| JAN Express Centre Ltd | Wholesale & retail | 2025 |
| Janapp Services Limited | Health & social care | 2014 |
| Janb Ltd | Construction | 2025 |
| Janba Constructions Ltd | Construction | 2024 |
| Janda London Associates Ltd | Manufacturing | 2016 |
| Jannat Properties Ltd | Real estate | 2025 |
| Jashanti Listen - in - Harmony Limited | Other services | 2006 |
| Jashu Ltd | Professional & scientific | 2024 |
| Jason Spencer Rees Advisory Limited | Professional & scientific | 2025 |
| Jasonmation Ltd | Arts & recreation | 2013 |
| JAY CUT - Unisex Salon Limited | Other services | 2020 |
| JAY Smart Ltd | Wholesale & retail | 2020 |
| Jaytalor Limited | Administrative & support | 2016 |
| Jbcinc Ltd | Professional & scientific | 2025 |
| JBJ Cleaning Limited | Administrative & support | 2020 |
| JBJ Healthcare Solution Ltd | Health & social care | 2024 |
| Jbmadeconstruction Ltd | Construction | 2024 |
| JBP Property Services Limited | Construction | 2008 |
| JC Digicom Ltd | Information & communication | 2025 |
| JCS Solutions Limited | Arts & recreation | 2006 |
| JDM Fuel Ltd | Wholesale & retail | 2026 |
| JDM Trading Group Ltd | Administrative & support | 2020 |
| JDZ Global Ltd | Manufacturing | 2023 |
| Jeeva Petroleum Company Limited | Wholesale & retail | 2017 |
| Jeeva Properties Company Ltd | Real estate | 2026 |
| Jeevan (UK) Limited | Real estate | 2009 |
| Jejaima Ltd | Health & social care | 2013 |
| Jelep Markets Ltd | Professional & scientific | 2025 |
| Jelesack Ltd | Wholesale & retail | 2025 |
| Jellus Padel Ltd | Wholesale & retail | 2024 |