| IN House Inc Ltd | Arts & recreation | 2011 |
| Inana Limited | Health & social care | 2022 |
| INB Advisory Limited | Financial services | 2007 |
| Inclusive Digital Limited | Information & communication | 2007 |
| Independent Childcare Group of Schools Limited | Extraterritorial | 1990 |
| Independent Data Solutions Limited | Information & communication | 2025 |
| Independent Flooring Validation Ltd | Wholesale & retail | 2009 |
| Independent Reliable Access Scaffolding Ltd | Construction | 2019 |
| India Association Limited | Other services | 2001 |
| Indigo Kite Limited | Information & communication | 2007 |
| Indigo Sapphfire Ltd | Health & social care | 2024 |
| Indinite Ltd | Information & communication | 2024 |
| Indira Properties Ltd | Real estate | 2025 |
| Indus Digital Limited | Information & communication | 2023 |
| Industria Bearings and Transmissions Limited | Wholesale & retail | 2006 |
| Indyd Ltd | Hospitality | 2023 |
| Inertia Structures Ltd | Professional & scientific | 2011 |
| Infinite Enterprises Limited | Information & communication | 2018 |
| Infinite Interior Design Limited | Manufacturing | 2025 |
| Infinity Delivery Ltd | Transport & logistics | 2023 |
| Infinity HI Ltd | Construction | 2024 |
| Influitiveibotta Ltd | Wholesale & retail | 2024 |
| Info Edge Limited | Wholesale & retail | 2023 |
| Infocus Security Systems Limited | Administrative & support | 2000 |
| Infogami Ltd | Information & communication | 2013 |
| Infonail Limited | Information & communication | 2025 |
| Informanagement UK Limited | Administrative & support | 2008 |
| Infrastructure Financial Management UK Ltd | Administrative & support | 2010 |
| Infrastructure Investments (Buxton) Limited | Administrative & support | 2004 |
| Infrastructure Investments (Leicester 2) Limited | Administrative & support | 2013 |
| Infrastructure Investments (Leicester) Limited | Administrative & support | 2013 |
| Infrastructure Investments Limited | Construction | 2003 |
| Infringo Ltd | Professional & scientific | 2025 |
| Infybee Limited | Wholesale & retail | 2023 |
| Inhabit Property Limited | Real estate | 2022 |
| Inhoco 2993 Limited | Professional & scientific | 2003 |
| Inhousebutchery Ltd | Hospitality | 2025 |
| Injury Helpline Limited | Extraterritorial | 1991 |
| Injury Hotline Limited | Extraterritorial | 1991 |
| INK AI Ltd | Information & communication | 2025 |
| Inkcredible Print Ltd | Manufacturing | 2026 |
| INNOV8IVE Investment Company Limited | Real estate | 2002 |
| Innovation and Growth Partners Ltd | Professional & scientific | 2018 |
| Innovationetc Limited | Information & communication | 2019 |
| Innovative Glass Solutions Ltd | Manufacturing | 2023 |
| Innovclean Ltd | Administrative & support | 2024 |
| Innovite UK Limited | Information & communication | 2014 |
| Inovage UK Limited | Information & communication | 2023 |
| INP Services Ltd | Administrative & support | 2025 |
| Inplas Fabrications Limited | Manufacturing | 2003 |
| Inplay Labs Ltd | Information & communication | 2019 |
| Inprojex Holdings Limited | Financial services | 2013 |
| Inscription Autos Ltd | Wholesale & retail | 2021 |
| Inside and OUT Maintenance Limited | Construction | 2010 |
| Insight Hearing Ltd | Wholesale & retail | 2023 |
| Insight UK Consultants Limited | Real estate | 2017 |
| Insightedge Consulting Ltd | Administrative & support | 2025 |
| INSPIRE-108 Ltd | Education | 2024 |
| Inspired Cleaning Services Ltd | Administrative & support | 2020 |
| Inspired Property Investment Limited | Real estate | 2017 |
| Inspiretrue Ltd | Transport & logistics | 2025 |
| Install & Build Ltd | Construction | 2020 |
| Instant Buy Ltd | Wholesale & retail | 2022 |
| Integra Control Solutions (EOT) Limited | Manufacturing | 2024 |
| Integra Control Solutions Limited | Administrative & support | 2006 |
| Integrated Build and Energy Ltd | Households | 2025 |
| INTEGRITY21 Ltd | Professional & scientific | 2021 |
| Intelliagent Limited | Information & communication | 2017 |
| Intellian Limited | Information & communication | 2011 |
| Intelligent Esubmissions Limited | Real estate | 2015 |
| Intelligent Membrane Consultants (IMC) Ltd | Construction | 2019 |
| Intelligent Security and Fire Limited | Professional & scientific | 2007 |
| Intelliwork Software Limited | Information & communication | 2022 |
| Inter-Global Holdings and Investments UK Limited | Households | 2024 |
| Inter-Mundial Investments Ltd | Households | 2024 |
| Inter-Tierra Investments Limited | Professional & scientific | 2011 |
| Interact Care Limited | Health & social care | 2003 |
| Interaction Graphics Limited | Professional & scientific | 1994 |
| Interdev Ltd | Professional & scientific | 2017 |
| Interface UK Limited | Administrative & support | 2001 |
| Interfit Interiors Limited | Construction | 2008 |
| Interiors by RIZ Ltd | Construction | 2021 |
| International Apex Management Group Ltd | Financial services | 2023 |
| International Commoditization Limited | Wholesale & retail | 2025 |
| International London Premises Limited | Real estate | 2025 |
| International Rooms Limited | Hospitality | 2013 |
| International Total Services (Holdings) Ltd | Administrative & support | 2017 |
| International Toys & Leisure Ltd | Wholesale & retail | 2024 |
| International Wellbeing Insights Ltd | Other services | 2003 |
| Interscan Limited | Transport & logistics | 2023 |
| Intersella Ltd | Wholesale & retail | 2024 |
| Interstellar Entertainment Limited | Manufacturing | 2023 |
| Intimate Trading Ltd | Wholesale & retail | 2022 |
| Intramex Trading Ltd | Wholesale & retail | 2022 |
| Introworld Ltd | Financial services | 2024 |
| Intu CUT Ltd | Other services | 2020 |
| Inventiv Solutions Limited | Administrative & support | 2023 |
| Inventsis Ltd | Manufacturing | 2011 |
| Invest and Grow Rich Ltd | Real estate | 2021 |
| Invest Construction Group Ltd | Construction | 2019 |