| Insulation & Heating Installations Ltd | Construction | 2017 |
| Insulpro Limited | Wholesale & retail | 2021 |
| Intaba Limited | Professional & scientific | 2018 |
| Integral Compliance Ltd | Professional & scientific | 2024 |
| Integral Security Systems Ltd | Administrative & support | 2018 |
| Integrated Management System Solutions Ltd | Construction | 2011 |
| Integrity Inspection Services Limited | Professional & scientific | 2019 |
| Intek Electrical Engineering Ltd | Professional & scientific | 2021 |
| Intelect (UK) Limited | Construction | 1997 |
| Intelect Mechanical Limited | Administrative & support | 2005 |
| Intelect Midlands Limited | Construction | 2013 |
| Intelligent Monitoring Solutions Ltd | Administrative & support | 2020 |
| Intelligent Security Group Ltd | Administrative & support | 2024 |
| Intellitrade Connect Ltd | Information & communication | 2026 |
| Intercontinental Brands (ICB) Limited | Manufacturing | 1990 |
| Intercontinental Brands Distillery Limited | Manufacturing | 2023 |
| Interiors by Tracey & Reuben Limited | Wholesale & retail | 2023 |
| Intermodal Tank Transport Group UK Limited | Transport & logistics | 2009 |
| Intermodal Tank Transport Logistics UK Limited | Transport & logistics | 2009 |
| International Assessment Centre Ltd | Professional & scientific | 2017 |
| International Haccp Certification Ltd. | Wholesale & retail | 1996 |
| International Instrument Services Ltd | Construction | 2023 |
| International Space Station (ISS) Logistics Limited | Wholesale & retail | 2025 |
| International Wind Services Ltd | Construction | 2025 |
| Internet Innovators Ltd | Information & communication | 2011 |
| Interpres Limited | Professional & scientific | 2024 |
| Intersearch Global Ltd | Professional & scientific | 2019 |
| Intershoe Limited | Wholesale & retail | 1968 |
| Interwind Site Services Ltd | Construction | 2022 |
| Intology Ltd | Information & communication | 2011 |
| Intraforce Ltd | Administrative & support | 2020 |
| Invenico Estates Limited | Real estate | 2024 |
| Invessa Limited | Wholesale & retail | 2016 |
| Investa Estates INT Ltd | Real estate | 2024 |
| Invested Childcare Holdings Ltd | Financial services | 2025 |
| Invested Childcare Ltd | Health & social care | 2017 |
| Investvise Ltd | Real estate | 2025 |
| Invicti Professional Ltd | Professional & scientific | 2024 |
| Invictus Securities Ltd | Administrative & support | 2015 |
| Inwood Property & Investments Limited | Real estate | 2021 |
| Ionut Calin Logistics Limited | Transport & logistics | 2025 |
| Iopq Limited | Professional & scientific | 2019 |
| Iotavx Licencing Limited | Administrative & support | 2021 |
| IP Private Gym Ltd | Arts & recreation | 2026 |
| Iphone Boro Limited | Wholesale & retail | 2025 |
| Iphone FIX Online Limited | Wholesale & retail | 2014 |
| IR Shop Ltd | Wholesale & retail | 2023 |
| IR Transport Ltd | Transport & logistics | 2024 |
| Irfan SRA Ltd | Wholesale & retail | 2025 |
| Iron Forecourt Services Ltd | Wholesale & retail | 2017 |
| Iron Services Limited | Construction | 2022 |
| Irona Construction Ltd | Construction | 2012 |
| Ironed OUT Ltd | Other services | 2017 |
| Ironstone Academy Trust | Education | 2014 |
| Ironstone Holdings Limited | Mining & quarrying | 2023 |
| Ironstone Technical Limited | Professional & scientific | 2018 |
| Irslifting Ltd | Construction | 2025 |
| Irvine Construction Consultants Ltd | Construction | 2022 |
| Isatoubojang Limited | Health & social care | 2019 |
| ISM Engineering Ltd | Professional & scientific | 2024 |
| Ispe United Kingdom Affiliate Limited | Education | 2011 |
| IT Many Logistics Limited | Transport & logistics | 2025 |
| It-Ot Consulting Ltd | Information & communication | 2022 |
| ITS Operating Group Ltd | Financial services | 2024 |
| Ivaf Holding a Ltd | Financial services | 2018 |
| Iveo Limited | Professional & scientific | 2024 |
| IVS Prestige Ltd | Wholesale & retail | 2018 |
| IWE Electrical Services Ltd | Administrative & support | 2005 |
| Izmir Northeast Ltd | Hospitality | 2019 |
| J & B Lifting & Rigging Solutions Ltd | Administrative & support | 2015 |
| J & C Climate Limited | Professional & scientific | 2025 |
| J & C Property Rentals Ltd | Real estate | 2021 |
| J & F Engineering Limited | Professional & scientific | 2014 |
| J & F Partners Ltd | Real estate | 2023 |
| J & J Properties (NE) Limited | Real estate | 2022 |
| J & P Lettings Limited | Real estate | 2020 |
| J a Williams Communications Ltd | Information & communication | 2021 |
| J Brass Group Ltd | Manufacturing | 2023 |
| J Carter Communications Ltd | Information & communication | 2025 |
| J Consultancy Services Ltd | Professional & scientific | 2026 |
| J Dobson Ltd | Construction | 2019 |
| J Duffy Industrial Trading Limited | Administrative & support | 2016 |
| J E Winter Haulage Limited | Transport & logistics | 2002 |
| J Graham Engineering Limited | Manufacturing | 2025 |
| J Gunn Scaffolding Limited | Construction | 2010 |
| J J G Property Management Limited | Households | 2020 |
| J L Quality Services Ltd | Professional & scientific | 2016 |
| J Lees Engineering Ltd | Construction | 2015 |
| J Linsley Civils Ltd | Construction | 2025 |
| J M Hackett Limited | Professional & scientific | 2018 |
| J M Hoggarth Rope Access Services Ltd | Professional & scientific | 2015 |
| J M Mortgage Services Limited | Financial services | 2003 |
| J Mcnamara Properties Limited | Real estate | 2020 |
| J Munroe Ltd | Construction | 2019 |
| J Oliver Services Limited | Professional & scientific | 2022 |
| J Palfreeman Rigging Ltd | Mining & quarrying | 2022 |
| J R K Motors Limited | Wholesale & retail | 2016 |
| J R P Jones & Associates Limited | Health & social care | 2008 |
| J R Stephenson Ltd | Administrative & support | 2022 |
| J RA Rigging Ltd | Mining & quarrying | 2026 |