| Indigo Artisan Ltd | Wholesale & retail | 2021 |
| Indigo Business Holdings Limited | Extraterritorial | 2004 |
| Indigo Business Services Limited | Professional & scientific | 2001 |
| Indigo Development Limited | Construction | 2009 |
| Indigo London Limited | Wholesale & retail | 2021 |
| Indigo Serra Ltd | Administrative & support | 2011 |
| Indra Housing Limited | Real estate | 2023 |
| Indraya Limited | Arts & recreation | 2025 |
| Industrial Scripts Ltd | Arts & recreation | 2010 |
| Infinita Search Ltd | Administrative & support | 2013 |
| Infinite Engineering Services Ltd | Professional & scientific | 2023 |
| Infinity External Services Ltd | Construction | 2023 |
| Infinity London Ltd | Other services | 2011 |
| Infracapital (IT PPP) Holdings Limited | Financial services | 2016 |
| Ingenovate Ltd | Professional & scientific | 2025 |
| Inglewall Limited | Transport & logistics | 2018 |
| Ingram & Ingram Limited | Hospitality | 2017 |
| Inner Vision Massage Ltd | Other services | 2024 |
| Innoteza Limited | Wholesale & retail | 2025 |
| Innovate Career Training Limited | Information & communication | 2023 |
| Innovate Vehicle Leasing Ltd | Administrative & support | 2026 |
| Innovatech Africa Ltd | Financial services | 2024 |
| Inocular Limited | Professional & scientific | 2020 |
| Inovapharm Limited | Professional & scientific | 2021 |
| Inovex Enterprise Limited | Wholesale & retail | 2026 |
| INP Marketing Ltd | Professional & scientific | 2025 |
| Insightful IT Limited | Information & communication | 2015 |
| Inspection NDE Consultants Limited | Information & communication | 2013 |
| Instant Opportunities Limited | Administrative & support | 2010 |
| Instapin Limited | Information & communication | 2023 |
| Instatap Ltd | Financial services | 2021 |
| Intangible Business Limited | Professional & scientific | 2001 |
| Integ Management Ltd | Administrative & support | 2013 |
| Integrative Medicine and Wellbeing Ltd | Health & social care | 2022 |
| Integrity AI Ventures Limited | Information & communication | 2025 |
| Intel Futures Limited | Administrative & support | 2024 |
| Intelli-Call Limited | Information & communication | 2003 |
| Intellisaas Limited | Professional & scientific | 2026 |
| Inter-Action Training Limited | Other services | 2011 |
| Interactual Ltd | Manufacturing | 2011 |
| Interdoceo | Education | 2015 |
| Interglobal Assets Ltd | Administrative & support | 1999 |
| Interior Kinetics Limited | Real estate | 2014 |
| Interior White Limited | Wholesale & retail | 2018 |
| International Aesthetics Pro Ltd | Wholesale & retail | 2024 |
| International Food Information Service (Ifis Publishing) | Information & communication | 1998 |
| Internet Mate Ltd | Information & communication | 2011 |
| Internetwork Limited | Information & communication | 2003 |
| Interval International Limited | Other services | 1987 |
| Interval Leisure Group Management Limited | Professional & scientific | 2013 |
| Interval Leisure Group UK Holdings (NO.2) Limited | Professional & scientific | 2012 |
| Interval Leisure Group UK Holdings Limited | Professional & scientific | 2012 |
| Interval UK Holdings Limited | Professional & scientific | 1994 |
| Intex Consulting Ltd | Information & communication | 2013 |
| Intoscope Solutions Limited | Administrative & support | 2024 |
| Intralan (UK) Limited | Information & communication | 1995 |
| Intralan Investments Limited | Financial services | 2017 |
| Intralan Telecom Limited | Extraterritorial | 2002 |
| Intrinsic Executive Search Limited | Administrative & support | 2006 |
| Intu Industrial Ltd | Extraterritorial | 2014 |
| Intu Maritime Ltd | Extraterritorial | 2014 |
| Intuitive Inbox Ltd | Professional & scientific | 2020 |
| Intuitive Testing Ltd | Information & communication | 2011 |
| Inventive Events Ltd | Administrative & support | 2025 |
| Inventorium Limited | Administrative & support | 2006 |
| Invest Silver Ltd | Information & communication | 2023 |
| Investiprop Ltd | Real estate | 2020 |
| Iogen New Energies UK Ltd | Energy | 2026 |
| IOX Partners Ltd | Administrative & support | 2023 |
| IQ in IT Ltd | Information & communication | 2009 |
| IQ Management Consulting Ltd | Professional & scientific | 2016 |
| IRA Investments Ltd | Households | 2018 |
| IRA RE Commercial Ltd | Real estate | 2024 |
| Iris Providence Limited | Financial services | 2016 |
| Iris Works Limited | Information & communication | 2026 |
| Irongran Ltd | Professional & scientific | 2021 |
| Isabella Hammond Consulting Limited | Information & communication | 2023 |
| Isabella Place (HAM) Residents Management Company Limited | Real estate | 2004 |
| ISC Holdings Limited | Administrative & support | 2016 |
| ISC Institutional Service Center Limited | Administrative & support | 1983 |
| ISG Facades Ltd | Construction | 2026 |
| ISI Enterprize Ltd | Wholesale & retail | 2025 |
| Isidro Heredia Legal Services Ltd | Professional & scientific | 2019 |
| Isight Asset Management Ltd | Real estate | 2026 |
| Isight Consultancy Ltd | Information & communication | 2015 |
| Island Hospice and Bereavement Service (UK) | Administrative & support | 2001 |
| Islay Subsurface & Engineering Ltd | Professional & scientific | 2010 |
| Isofit Limited | Arts & recreation | 2022 |
| Isomarble Limited | Manufacturing | 2018 |
| IT 4 DT London Limited | Information & communication | 2018 |
| IT 4 Everyone Ltd | Wholesale & retail | 2020 |
| IT Green Light Limited | Information & communication | 2011 |
| IT Renovation and Consultancy Ltd | Information & communication | 2025 |
| IT4EO Ltd | Wholesale & retail | 2025 |
| Iteratio Ltd | Information & communication | 2018 |
| Iteration Consulting Ltd | Information & communication | 2015 |
| Ithaca Capital Limited | Administrative & support | 2004 |
| Itineris Software UK Limited | Information & communication | 2023 |
| Itman Resources Limited | Professional & scientific | 1999 |
| ITS Pure Limited | Manufacturing | 2011 |