| Inspection System Services Limited | Manufacturing | 2007 |
| Inspiration Design & Installation Limited | Construction | 2008 |
| Inspire Learning Trust | Education | 2015 |
| Inspire Living Properties Ltd | Real estate | 2024 |
| Inspired Foot Clinic Ltd | Health & social care | 2009 |
| Inspired Growth Limited | Professional & scientific | 2026 |
| Inspiritlife Ltd | Information & communication | 2023 |
| Instincts Training Ltd | Education | 2022 |
| Insulate and Ventilate Ltd | Construction | 2024 |
| Insutek Ltd | Construction | 2024 |
| Intake Electrical Contractors Limited | Energy | 2008 |
| Intake Holdings Ltd | Financial services | 2025 |
| Intake Properties Ltd | Real estate | 2025 |
| Intalabel Limited | Manufacturing | 2002 |
| Integral Biopharma Ltd | Health & social care | 2020 |
| Integrated Compliance Consulting Ltd | Professional & scientific | 2026 |
| Integrated Facilities Management Ltd | Construction | 2024 |
| Integrated Scientific AIM Ltd | Manufacturing | 2023 |
| Integrated Scientific Limited | Manufacturing | 1988 |
| Integration Healthcare Services Ltd | Health & social care | 2016 |
| Integrity Quartz Ltd | Extraterritorial | 2020 |
| Intelligent Leasing Limited | Financial services | 2007 |
| Intelligent Metal Solutions Limited | Water & waste | 2014 |
| Intelligent Network Design Limited | Administrative & support | 2018 |
| Intelligent PMI Limited | Financial services | 2012 |
| Inter Solutio Ltd | Wholesale & retail | 2016 |
| Interchange Cafe Limited | Hospitality | 2016 |
| Interconnector Execution Ltd | Professional & scientific | 2024 |
| Interior Decorations of Broomhill Limited | Wholesale & retail | 1959 |
| Interior Solutions (SY) Ltd | Construction | 2011 |
| Intermet Refractory Products Limited | Manufacturing | 2008 |
| International Sporting Falcons Limited | Agriculture & fishing | 2018 |
| International Stones (UK) Limited | Wholesale & retail | 2009 |
| International Tank Services Limited | Construction | 2025 |
| Internet Media Productions Ltd | Information & communication | 2003 |
| Intimate WAX Expert Limited | Other services | 2024 |
| Intocast UK Limited | Wholesale & retail | 2003 |
| Inversion Consultancy & Solutions Limited | Information & communication | 2015 |
| Investments & Assets Ltd | Real estate | 2025 |
| Invictus Dentistry Limited | Health & social care | 2022 |
| Inviolable Limited | Professional & scientific | 2025 |
| Invitech Ltd | Wholesale & retail | 2008 |
| Ioan Angel Limited | Transport & logistics | 2025 |
| Ionut Paul Serdean Limited | Transport & logistics | 2020 |
| Iplumb Direct Limited | Construction | 2020 |
| Iprema Ltd | Wholesale & retail | 2020 |
| Iprosurv Limited | Professional & scientific | 2014 |
| IPS Electrical Testing Services Ltd | Construction | 2015 |
| Iptk Ltd | Professional & scientific | 2022 |
| IQ Publishing Ltd | Administrative & support | 2015 |
| Irave Globle Ltd | Wholesale & retail | 2026 |
| Irene Knight Fashion & Design Ltd | Wholesale & retail | 2021 |
| Iron Comms Rigging Limited | Information & communication | 2025 |
| Iron Eagle Trunks Ltd | Manufacturing | 2025 |
| Ironclad Golf and Apparel Ltd | Wholesale & retail | 2025 |
| Ironstone Group Limited | Wholesale & retail | 2018 |
| Ironworks Doncaster Limited | Arts & recreation | 2022 |
| Irvine Electrical Ltd | Information & communication | 2014 |
| Irys Logistics Ltd | Transport & logistics | 2015 |
| IS Easy Haul Ltd | Transport & logistics | 2020 |
| Isabella Harley Limited | Real estate | 2021 |
| Isabella James Estates Ltd | Real estate | 2024 |
| ISF Rotherham Properties Ltd | Real estate | 2025 |
| Island House Developments Ltd | Financial services | 2023 |
| ISN Estates Limited | Real estate | 2025 |
| Isobella's Limited | Hospitality | 2015 |
| Isolutions Consulting Limited | Information & communication | 2025 |
| Istanbul Barber Limited | Other services | 2023 |
| Istones Holdings Limited | Financial services | 2022 |
| Istones North Limited | Real estate | 2020 |
| IT Desk (UK) Limited | Information & communication | 2006 |
| IT Gadgets Ltd | Manufacturing | 2024 |
| IT Hardware Experts Ltd | Wholesale & retail | 2025 |
| IT PR Consultants Ltd | Professional & scientific | 2026 |
| IT Smart Solutions Ltd | Information & communication | 2025 |
| IT4U Consulting Ltd | Information & communication | 2015 |
| Italia & Crust Limited | Hospitality | 2026 |
| Italy Review Ltd | Administrative & support | 2023 |
| Ithilien Limited | Information & communication | 2023 |
| ITR International Time Limited | Extraterritorial | 1952 |
| Itrap Technologies Limited | Manufacturing | 2017 |
| Itzen Ltd | Information & communication | 2019 |
| It’S ME BAD DAD Ltd | Professional & scientific | 2024 |
| It’S ME BAD MUM Beauty Ltd | Professional & scientific | 2025 |
| It’S ME BAD MUM Homeware Ltd | Professional & scientific | 2025 |
| It’S ME BAD MUM Ltd | Professional & scientific | 2024 |
| It’S ME BAD MUM Technology Ltd | Professional & scientific | 2025 |
| Iulianrusu Limited | Transport & logistics | 2024 |
| Ivan Removals Ltd | Water & waste | 2018 |
| Ivan Stores Ltd | Wholesale & retail | 2025 |
| Ivancy Financial Solutions Ltd | Financial services | 2026 |
| Ivazo Housing Ltd | Construction | 2025 |
| IVY Cottage Commercial Services Limited | Professional & scientific | 2022 |
| Iwaan Projects Ltd | Wholesale & retail | 2025 |
| Iwojack Ltd | Administrative & support | 2017 |
| IZ Vision Ltd | Health & social care | 2025 |
| Izec Prestige Cars Ltd | Transport & logistics | 2022 |
| Izyan Properties Limited | Real estate | 2023 |
| Izzymax Rendering Services Ltd | Construction | 2016 |
| J & a Lewis Invest Ltd | Real estate | 2024 |