| Information Quotient Software Services Limited | Information & communication | 2004 |
| Informcomm Limited | Education | 2008 |
| Infosiri Limited | Information & communication | 2015 |
| Infospectives Ltd | Information & communication | 2015 |
| Infotechuk Limited | Information & communication | 2011 |
| Infovance Solutions Ltd | Information & communication | 2025 |
| Infra DEV CON Limited | Professional & scientific | 2011 |
| Infrabim Studio Limited | Professional & scientific | 2022 |
| Infraclean Tech Limited | Administrative & support | 2019 |
| Infradev Contracting Limited | Construction | 2015 |
| Infradev Holdings Limited | Real estate | 2023 |
| Infranest Solutions Limited | Information & communication | 2025 |
| Infrastructure Design Solutions Ltd | Information & communication | 2011 |
| Infrateq Group UK Ltd | Information & communication | 2021 |
| Infusion Events Management Limited | Other services | 2023 |
| Ingene Publishers Limited | Information & communication | 2022 |
| Ingenium Construction Services Limited | Construction | 2012 |
| Ingenium Tech Ltd | Information & communication | 2025 |
| Ingenuity Assets Limited | Financial services | 2022 |
| Ingenuity Manor Ltd | Real estate | 2025 |
| Ingenuity Ware Limited | Information & communication | 2014 |
| Ingles of Garstang Limited | Construction | 1965 |
| Ingodi Ltd | Wholesale & retail | 2019 |
| Ingram Micro (UK) Limited | Wholesale & retail | 1982 |
| Ingram Micro Holdings Limited | Professional & scientific | 1985 |
| Inhale and Breathe Ltd | Health & social care | 2026 |
| Inhaus Developments Ltd | Construction | 2022 |
| Inhaus Properties LLP | | 2021 |
| Inhouse Pack (UK) Limited | Manufacturing | 2020 |
| Iniad Tech Solutions Limited | Information & communication | 2021 |
| Inidi Entertainment Limited | Information & communication | 2023 |
| INIT2WINIT Limited | Arts & recreation | 2024 |
| Inium Ltd | Information & communication | 2022 |
| Injury 2 Fitness Ltd | Other services | 2025 |
| INK and Toner Recycling Ltd | Water & waste | 2012 |
| Inkantations Limited | Other services | 2018 |
| Inked Moose Ltd | Arts & recreation | 2014 |
| Inkjoygraphy Ltd | Arts & recreation | 2022 |
| Inklink Studio Ltd | Information & communication | 2025 |
| Inlink Solutions Ltd | Transport & logistics | 2026 |
| Inmass Limited | Manufacturing | 2004 |
| Inmirage Ltd | Information & communication | 2024 |
| Inn Scented Limited | Real estate | 2025 |
| Innately Expressed Ltd | Administrative & support | 2023 |
| Innecto People Consulting Limited | Professional & scientific | 2003 |
| Inner Create Limited | Construction | 2015 |
| Inner Develop Ltd | Construction | 2024 |
| Inner Dezire Modelling. Limited | Other services | 2014 |
| Inner Frequency Ltd | Administrative & support | 2020 |
| Inner Sense Supplements Limited | Health & social care | 2024 |
| Inngo Properties Limited | Real estate | 2025 |
| Innocent Trading Limited | Wholesale & retail | 2017 |
| Innoshift Technologies Ltd | Information & communication | 2025 |
| Innotechforce Limited | Wholesale & retail | 2025 |
| Innova Engineering Consultants Limited | Professional & scientific | 2025 |
| Innovate Tech Limited | Professional & scientific | 2017 |
| Innovation Energy Experts Ltd | Wholesale & retail | 2011 |
| Innovation Imperative Limited | Professional & scientific | 2000 |
| Innovations (Home Counties) CIC | Public administration | 2020 |
| Innovatis Ltd | Wholesale & retail | 2024 |
| Innovative Ecom Limited | Wholesale & retail | 2020 |
| Innovative Ideas UK Ltd | Wholesale & retail | 2008 |
| Innovative Marketing Services Limited | Administrative & support | 2001 |
| Innovative Quest Ltd | Information & communication | 2012 |
| Innovative Solutions PVT Limited | Information & communication | 2011 |
| Innovative Treatment Solutions (ITS) Limited | Professional & scientific | 2006 |
| Innovative, Trusted and Personal Care Limited | Administrative & support | 2017 |
| Innoveat Group Ltd | Hospitality | 2021 |
| Innovelec Solutions Limited | Wholesale & retail | 2009 |
| Innovic Solutions Limited | Information & communication | 2024 |
| Innovision IP Ltd | Information & communication | 2019 |
| Innoviz Limited | Information & communication | 2018 |
| Innovorisk Ltd | Information & communication | 2010 |
| Innoxite Limited | Extraterritorial | 2015 |
| Inns & Outs Ltd | Hospitality | 2013 |
| Inond Ltd | Professional & scientific | 2018 |
| Inply Data Solutions Limited | Professional & scientific | 2026 |
| Inply Holding Limited | Financial services | 2026 |
| INR and Associates Ltd | Financial services | 2018 |
| INR Logistics Ltd | Transport & logistics | 2026 |
| Inreach Communications Limited | Information & communication | 2016 |
| Inreach Group Limited | Other services | 1998 |
| Inreach Holdings Limited | Professional & scientific | 2007 |
| Inreach I.T. Limited | Information & communication | 2019 |
| Inreach Intalk Limited | Information & communication | 2023 |
| Inreach Print Limited | Extraterritorial | 2015 |
| Inreach Talk Limited | Information & communication | 2022 |
| Inscale Limited | Wholesale & retail | 2008 |
| Inside Holdings Limited | Real estate | 2018 |
| Inside Limited | Construction | 2017 |
| Insideout Culture Ltd | Professional & scientific | 2026 |
| Insideout Living Limited | Administrative & support | 2017 |
| Insight Financial Solutions Limited | Financial services | 2001 |
| Insight IT Ltd | Information & communication | 2025 |
| Insight Marketing and People Ltd | Professional & scientific | 1992 |
| Insight Nexus Consulting Ltd | Education | 2025 |
| Insight Pictures Limited | Administrative & support | 2020 |
| Insight Plumbing & GAS Limited | Construction | 2019 |
| Insight Works Consultancy Ltd | Professional & scientific | 2026 |
| Insightable Data Ltd | Wholesale & retail | 2022 |