| Info Veriti Capital Investments Limited | Extraterritorial | 2007 |
| Infobee Limited | Professional & scientific | 2018 |
| Infomax Consults Limited | Information & communication | 2025 |
| Infratechna Limited | Construction | 2014 |
| Ingenious Technologies Limited | Information & communication | 2012 |
| Ingenium Electrical Limited | Professional & scientific | 2018 |
| Inhurst Developments Ltd | Construction | 2015 |
| INITI8 Consultancy Services Ltd | Professional & scientific | 2020 |
| INITI8 Recruitment Limited | Professional & scientific | 2008 |
| Injeanious Ltd | Wholesale & retail | 2007 |
| Ink&Hairacademy Limited | Education | 2025 |
| Inkbound Ltd | Arts & recreation | 2021 |
| Inline Building Limited | Construction | 2022 |
| Innaun Limited | Information & communication | 2024 |
| Inner Estate Ltd | Real estate | 2010 |
| Inner Estate Management LLP | | 2017 |
| Innerscapes by Sara Ltd | Professional & scientific | 2025 |
| Innovasia Limited | Wholesale & retail | 2005 |
| Innovative Career Solutions Limited | Administrative & support | 2005 |
| Innovators International Limited | Wholesale & retail | 1988 |
| Insane Icon Limited | Arts & recreation | 2001 |
| Insatiable International Ltd | Arts & recreation | 2007 |
| Insideoutrefurb Ltd | Construction | 2005 |
| Inspireall Leisure and Family Support Services | Arts & recreation | 2001 |
| Inspireat Ltd | Professional & scientific | 2020 |
| Inspired Asset Holdings Limited | Financial services | 2012 |
| Inspired Bespoke Joinery Ltd | Construction | 2017 |
| Inspired Films Limited | Information & communication | 2010 |
| Inspired Royalties Limited | Information & communication | 2017 |
| Inspra Tea UK Limited | Wholesale & retail | 2023 |
| Instyle Building and Design Limited | Construction | 2015 |
| Integrabooks Limited | Professional & scientific | 2019 |
| Intelligensa Limited | Education | 2013 |
| Intelligent Thinking (UK) Ltd | Information & communication | 2014 |
| Interactive Imagination Ltd. | Information & communication | 1999 |
| Intercel (UK) Limited | Administrative & support | 2011 |
| Interesting Investments Limited | Professional & scientific | 2013 |
| Interior Transformers Limited | Construction | 2012 |
| Intermetro Limited | Manufacturing | 2015 |
| International Business Consultants Group Ltd | Professional & scientific | 2019 |
| International Computer Security Holdings Ltd | Information & communication | 1996 |
| International Timed Services Limited | Administrative & support | 2009 |
| Interstellar Mapping Ltd | Professional & scientific | 2024 |
| Intertrade Exchange Ltd | Financial services | 2021 |
| Intertrade Global Limited | Financial services | 2021 |
| Intex Film and TV Ltd | Arts & recreation | 2022 |
| Intor Consulting Ltd | Information & communication | 2017 |
| Intouchnow Services Limited | Information & communication | 2019 |
| Intrinsic MA Limited | Other services | 2022 |
| Intrinsic Media Group Limited | Professional & scientific | 1992 |
| Intrust Care Ltd | Health & social care | 2016 |
| Invate AI Limited | Information & communication | 2025 |
| Investerco Limited | Financial services | 2024 |
| Investmark Group Limited | Real estate | 2019 |
| Investment Mastery Limited | Professional & scientific | 2004 |
| Investmoor Limited | Financial services | 2024 |
| Investor Meet Company Limited | Professional & scientific | 2018 |
| Invicta Moulds Limited | Manufacturing | 2000 |
| Invictus Nova Ltd | Agriculture & fishing | 2019 |
| Invictus Pension and Investment Portfolios Limited | Financial services | 2016 |
| Invo Plus Ltd | Information & communication | 2023 |
| Involute Industries Ltd. | Manufacturing | 2019 |
| IOA IT Consulting Ltd | Information & communication | 2018 |
| Iohs Ltd | Health & social care | 2022 |
| Iosif Apetroaei Ltd | Transport & logistics | 2019 |
| IP Labs Communications Limited | Information & communication | 2014 |
| IPH Insurance Services (UK) Limited | Financial services | 1998 |
| IPL Fittings Ltd | Construction | 2025 |
| IPL UK Construction Ltd | Construction | 2025 |
| Iplus Tech Professional Services Limited | Professional & scientific | 2018 |
| Ipswich Container Transport Ltd | Transport & logistics | 2018 |
| Ipswich Investments Limited | Real estate | 2010 |
| IQ Consultancy and Management Limited | Professional & scientific | 2011 |
| IQ Event & Logistics Services Limited | Hospitality | 2023 |
| IQ Property Management & Investments Limited | Real estate | 2023 |
| Irellandnews&Booze Ltd | Wholesale & retail | 2019 |
| Irem Railway Engineering Ltd | Professional & scientific | 2024 |
| Irenaeus Technology Limited | Information & communication | 2026 |
| Iridium Estates Ltd | Real estate | 2021 |
| Iron Enterprises Limited | Financial services | 2020 |
| Ironstone Freeholds Ltd | Construction | 2024 |
| Ironstone House Beckenham Limited | Financial services | 2023 |
| Ironstone Ltd | Construction | 2024 |
| Ironstone Real Estate Ltd | Construction | 2024 |
| IRU Property Ltd | Real estate | 2018 |
| Isco Investments Limited | Real estate | 2019 |
| Isco Real Estate Limited | Real estate | 2019 |
| Isff Social Ltd | Professional & scientific | 2026 |
| Isher Capital Limited | Financial services | 2020 |
| Ishu World Limited | Manufacturing | 2021 |
| Isingh Property Services Ltd | Real estate | 2023 |
| Island Pool Ltd | Hospitality | 2022 |
| Islin Wealth Management Limited | Financial services | 2019 |
| Ismail Consulting Partners Ltd | Professional & scientific | 2017 |
| Isp&Co Ltd | Hospitality | 2022 |
| Istvan Limited | Transport & logistics | 2018 |
| Isurgeon Ltd | Health & social care | 2020 |
| IT ERP Limited | Information & communication | 2015 |
| IT Never Ends Limited | Wholesale & retail | 2024 |
| IT Outlet Store Limited | Wholesale & retail | 2020 |