| Intelligent Performance Limited | Information & communication | 2004 |
| Interbrew Limited | Hospitality | 2025 |
| Intercall Nursecall Systems Ltd | Professional & scientific | 2003 |
| Interchange Systems Ltd | Information & communication | 2025 |
| Intercleanse (Pest Control) Limited | Administrative & support | 2007 |
| Interclubz Limited | Information & communication | 2016 |
| Interconstruct Ltd | Construction | 2012 |
| International Contracts Limited | Wholesale & retail | 2018 |
| International Corporate Media Limited | Information & communication | 2008 |
| International Rugby Academy New Zealand - UK Ltd | Education | 2025 |
| International Sports Marketing Limited | Information & communication | 2000 |
| Intown Managed Services Limited | Wholesale & retail | 2015 |
| Intrépido Partners Ltd | Wholesale & retail | 2025 |
| Invicta Animal Health Limited | Wholesale & retail | 2010 |
| Invictus Wealth Consultants Limited | Administrative & support | 2016 |
| Iolar Limited | Transport & logistics | 2015 |
| Ionic Technical Services Ltd | Water & waste | 2022 |
| IP Prime Estates Ltd | Real estate | 2026 |
| IP Syndicate Consortium Limited | Extraterritorial | 2017 |
| IP Syndicate Holdings Limited | Financial services | 2020 |
| IP Syndicate Limited | Extraterritorial | 2023 |
| Ipuk I Limited | Extraterritorial | 2019 |
| Ipuk II Limited | Extraterritorial | 2019 |
| Ipuk III Limited | Extraterritorial | 2019 |
| Ipuk IV Limited | Extraterritorial | 2019 |
| Ipuk IX Limited | Extraterritorial | 2023 |
| Ipuk V Limited | Extraterritorial | 2019 |
| Ipuk VI Limited | Extraterritorial | 2019 |
| Ipuk VII Limited | Extraterritorial | 2023 |
| Ipuk Viii Limited | Extraterritorial | 2023 |
| Ipuk X Limited | Extraterritorial | 2023 |
| Ipuk XI Limited | Extraterritorial | 2023 |
| Ipuk XII Limited | Extraterritorial | 2023 |
| Ipuk Xiii Limited | Extraterritorial | 2023 |
| Ipuk XIV Limited | Extraterritorial | 2023 |
| Ipuk XIX Limited | Extraterritorial | 2023 |
| Ipuk XV Limited | Extraterritorial | 2023 |
| Ipuk XVI Limited | Extraterritorial | 2023 |
| Ipuk Xvii Limited | Extraterritorial | 2023 |
| Ipuk Xviii Limited | Extraterritorial | 2023 |
| Ipuk XX Limited | Extraterritorial | 2023 |
| Iqei International Limited | Education | 2019 |
| Iqei Limited | Education | 2010 |
| Iranz UK Ltd | Extraterritorial | 2025 |
| Ironmongery Warehouse Direct Limited | Wholesale & retail | 2017 |
| Ironsoles Limited | Wholesale & retail | 2022 |
| Iskraemeco (UK) Limited | Energy | 1995 |
| ISM Search Limited | Administrative & support | 1990 |
| Ispace Glass Limited | Construction | 2018 |
| Istanbul Jewellers Ltd | Wholesale & retail | 2024 |
| Istoria AI Limited | Information & communication | 2021 |
| IT Engine Ltd | Administrative & support | 2018 |
| IT Remarketing Limited | Information & communication | 2024 |
| It-Moneywise Limited | Information & communication | 1985 |
| ITS Cycling Limited | Manufacturing | 2013 |
| Ivan Berry Productions Limited | Information & communication | 2025 |
| IVY Mill Day Nursery Ltd | Health & social care | 2021 |
| Ivycroft Ltd | Professional & scientific | 2023 |
| IW Leisure Limited | Other services | 1998 |
| Ixerv Uk/Ireland Ltd | Professional & scientific | 2011 |
| Izmir Enterprises Ltd | Hospitality | 2018 |
| J & E Wake Management Ltd | Professional & scientific | 2020 |
| J & G Hughes Construction Limited | Construction | 2020 |
| J & S Meadows Ltd | Real estate | 2018 |
| J & V Building Services Ltd | Construction | 2021 |
| J 7 Architecture Limited | Professional & scientific | 2003 |
| J C Services Southern Limited | Manufacturing | 2013 |
| J Dennison Plastering Ltd | Construction | 2020 |
| J F B Electrical Ltd | Construction | 2019 |
| J Lashmar & SON Limited | Construction | 2020 |
| J Mcarthur Limited | Information & communication | 2013 |
| J Messham Property Solutions Limited | Construction | 2026 |
| J T Dunlop Construction Limited | Construction | 2013 |
| J W Capital Investment Ltd | Financial services | 2026 |
| J W Webb Accountancy and Taxation Limited | Professional & scientific | 1984 |
| J&Dh Enterprises Limited | Real estate | 2018 |
| J. Tomes Limited | Professional & scientific | 2011 |
| J.A .Q Heating Limited | Construction | 2021 |
| J.A.C Automotive Ltd | Wholesale & retail | 2024 |
| J.A.S.S. Management Limited | Construction | 2019 |
| J.A.S.S. Property Limited | Real estate | 2019 |
| J.D. Richmond & SON Limited | Construction | 2008 |
| J.D.N. Limited | Real estate | 1982 |
| J.Iddon Contractors Ltd | Construction | 2023 |
| J.P.M. Limited | Arts & recreation | 1986 |
| J.R. Brown Electrical Ltd | Manufacturing | 2016 |
| J29:11 Solutions Ltd | Information & communication | 2019 |
| J70 Limited | Professional & scientific | 2022 |
| JAC Electrical Ltd | Construction | 2015 |
| Jack O. Durdle Limited | Real estate | 1962 |
| Jackson Nugent Vintners Limited | Wholesale & retail | 1979 |
| Jackson Tools Ltd | Wholesale & retail | 2009 |
| Jacques Consulting Ltd | Professional & scientific | 2019 |
| Jacqui Lloyd Ltd | Professional & scientific | 2025 |
| Jade Bridge Group Limited | Wholesale & retail | 2025 |
| Jade Cross Ltd | Health & social care | 2017 |
| Jaffer Johnston Limited | Information & communication | 2018 |
| Jajajo Limited | Administrative & support | 2019 |
| JAK Business Matters Ltd | Professional & scientific | 2011 |
| Jaks Projects Ltd | Construction | 2023 |