| Imperium Stamps Limited | Other services | 2014 |
| Implementing ERP Ltd | Information & communication | 2024 |
| Improve B2B Ltd | Professional & scientific | 2010 |
| IN 2 Cars Ltd | Wholesale & retail | 2026 |
| IN Life and Death Ltd | Other services | 2026 |
| IN Probuilders Ltd | Construction | 2026 |
| IN the Blue Corner Limited | Arts & recreation | 2024 |
| IN the Name of My Father (MR Arthur Palmer) Protesters and Whistleblowers Limited | Information & communication | 2023 |
| IN Vino Veritas Ltd | Wholesale & retail | 2002 |
| In-Tuition Support Ltd | Education | 2024 |
| Inboundly Ltd | Information & communication | 2008 |
| Inclusive Creator Network Limited | Wholesale & retail | 2025 |
| Independent Divorce Limited | Professional & scientific | 2009 |
| Independent Play Limited | Arts & recreation | 2019 |
| Indian Grills Room Limited | Hospitality | 2023 |
| Individual Stage Design Ltd | Arts & recreation | 2018 |
| Indoor Environmental Systems Limited | Construction | 2011 |
| Industrial Tooling Corporation Limited | Manufacturing | 1991 |
| Infinite Orbits Ltd | Information & communication | 2011 |
| Infinite Pest Management Ltd | Administrative & support | 2023 |
| Infinito Capital Ltd | Professional & scientific | 2024 |
| Infosec Risk and Compliance Consulting Ltd | Professional & scientific | 2011 |
| Infra Innovate Limited | Professional & scientific | 2024 |
| Infrastructure Corridor Energy Ltd | Energy | 2023 |
| Ingold Recruitment Limited | Administrative & support | 2009 |
| Ingold Recruitment Tamworth Ltd | Extraterritorial | 2023 |
| Ingram Retailing Limited | Financial services | 2015 |
| INI DEC Ltd | Construction | 2024 |
| Inishowen Planning Ltd | Professional & scientific | 2017 |
| Initial D Ltd | Education | 2022 |
| Inkspire Wall Printing Ltd | Manufacturing | 2025 |
| Inman Aligner Training Limited | Administrative & support | 2007 |
| Inmotion Football Performance Ltd | Education | 2025 |
| Innovation Facades Ltd | Construction | 2024 |
| Innovation Fast Ltd | Professional & scientific | 2015 |
| Innovations Connected Limited | Information & communication | 2010 |
| INOV-8 Electrical Services Ltd | Construction | 2024 |
| INOV-8 Group Holdings Ltd | Financial services | 2025 |
| Inoxko Global Holdings Ltd | Administrative & support | 2016 |
| Inoxko Ltd | Administrative & support | 2016 |
| Inp-Group Ltd | Administrative & support | 2020 |
| Insanely Great Guides Ltd | Information & communication | 2016 |
| Inside Lane Talent Ltd | Professional & scientific | 2026 |
| Insight Technology Group Ltd | Information & communication | 2018 |
| Inspect Effect Ltd | Construction | 2012 |
| Inspire Psychiatry Limited | Health & social care | 2014 |
| Install Electrical Contractors Limited | Professional & scientific | 2008 |
| Install Mechanical Contractors Ltd | Construction | 2015 |
| Install Only Limited | Construction | 2023 |
| Instyle Home Living Ltd | Construction | 2019 |
| Insulation Machining and Tooling Limited | Manufacturing | 2000 |
| Integrahire Limited | Administrative & support | 2025 |
| Integrity Education Solutions Limited | Administrative & support | 2024 |
| Integrum Contracts Ltd | Construction | 2020 |
| Intelligent Alignment Sciences Limited | Administrative & support | 2024 |
| Interlap Solutions Limited | Information & communication | 2016 |
| International Clearance Limited | Other services | 2025 |
| International Golf Travel Limited | Administrative & support | 2024 |
| International Orthopaedic Group Ltd | Professional & scientific | 2025 |
| Interpret Capital Limited | Information & communication | 2022 |
| Intersearch Worldwide Limited | Administrative & support | 1990 |
| Inteva Ltd | Professional & scientific | 2026 |
| Inti Energy Group Ltd | Construction | 2026 |
| Intisaa Associates Ltd | Professional & scientific | 2024 |
| Intransit (GB) Limited | Real estate | 2009 |
| Invest-Ed Limited | Professional & scientific | 2009 |
| Investmentwatch UK Limited | Other services | 2017 |
| Invictus Homes Limited | Real estate | 2017 |
| Invigortex Ltd | Wholesale & retail | 2023 |
| IPL Plastics (UK) Limited | Manufacturing | 2007 |
| IQ Asset Group Ltd | Information & communication | 2025 |
| IRB Automotive Limited | Wholesale & retail | 2025 |
| Irimiatransport Ltd | Transport & logistics | 2025 |
| Iron + Ivory Ltd | Other services | 2026 |
| Iron Oak Interiors Ltd | Construction | 2025 |
| Ironmongery Express Limited | Manufacturing | 2009 |
| IRT Accountancy Services Ltd | Extraterritorial | 2013 |
| Irtas Ltd | Professional & scientific | 2010 |
| Irønhavøc Ltd | Wholesale & retail | 2026 |
| Isatlas Ltd | Professional & scientific | 2019 |
| Isis Control Systems Limited | Construction | 2001 |
| Isobex Laser Supplies Limited | Wholesale & retail | 2025 |
| Isoton Limited | Real estate | 1986 |
| Ispas Haulage Ltd | Manufacturing | 2023 |
| IT Tech Equipment Ltd | Wholesale & retail | 2026 |
| Iubi Design 3D Limited | Wholesale & retail | 2023 |
| IVM Solutions Ltd | Transport & logistics | 2015 |
| Ivory and Slate Limited | Real estate | 2025 |
| Ivory Tusk Limited | Hospitality | 2005 |
| IZ Global Trading Limited | Wholesale & retail | 2020 |
| Izzy MAE Westwood Ltd | Extraterritorial | 2024 |
| J & a Dwellings Limited | Real estate | 2024 |
| J & G Salon Limited | Wholesale & retail | 2010 |
| J & J Plastics Holdings Ltd | Financial services | 2023 |
| J & J Plastics Ltd | Water & waste | 2013 |
| J & K Cleaning Ltd | Administrative & support | 2025 |
| J & K Traction Limited | Transport & logistics | 2012 |
| J & R Dinshaw Limited | Wholesale & retail | 2014 |
| J & R Stevens Limited | Wholesale & retail | 2020 |
| J & T Blackman Limited | Wholesale & retail | 2001 |