| Initiative Marketing Consultants Limited | Professional & scientific | 2025 |
| Injuria Limited | Administrative & support | 2007 |
| Inkblue Marketing Limited | Professional & scientific | 2024 |
| Inkk Limited | Professional & scientific | 2023 |
| INL Services Limited | Professional & scientific | 2018 |
| Inloom Fabrics Limited | Wholesale & retail | 2020 |
| Inner City Housing Ltd | Extraterritorial | 1985 |
| Innerva Holdings Ltd | Financial services | 2022 |
| Innerva Trustee Limited | Financial services | 2026 |
| Innfrastructure Limited | Professional & scientific | 2001 |
| Innova Ecommerce Limited | Wholesale & retail | 2023 |
| Innovaco Holdings Ltd | Construction | 2012 |
| Innovate MR, Ltd | Professional & scientific | 2017 |
| Innovate Orthopaedics Limited | Manufacturing | 2014 |
| Innovate YOU Ltd | Administrative & support | 2019 |
| Innovative Hearing Solutions Limited | Other services | 2024 |
| Inobee Ltd | Health & social care | 2024 |
| Inomorph Ltd | Professional & scientific | 2023 |
| Inpals OUT of School Club CIC | Health & social care | 2024 |
| Insertiagear Limited | Wholesale & retail | 2025 |
| Inside OUT Beauty From Within Ltd | Manufacturing | 2019 |
| Insight (PFM) Limited | Professional & scientific | 2020 |
| Insolvens Ltd | Professional & scientific | 2001 |
| Inspiration Computers Limited | Manufacturing | 2003 |
| Inspirations Plants & Gardens Ltd | Wholesale & retail | 2023 |
| Inspire Electrical & Interior Solutions Limited | Construction | 2016 |
| Inspire Training Solutions Limited | Professional & scientific | 2002 |
| Inspired Design (Yorkshire) Limited | Construction | 2017 |
| Inspirekind Care Services Ltd | Health & social care | 2025 |
| Inspoconia Ltd | Wholesale & retail | 2020 |
| Instant Entry Services Limited | Other services | 2023 |
| Instyle Property Management Limited | Real estate | 2025 |
| Insula Care and Support Ltd | Health & social care | 2021 |
| Insulink CIC | Health & social care | 2025 |
| Insydium Ltd | Information & communication | 2013 |
| INT Transport Ltd | Transport & logistics | 2016 |
| Intake Ltd | Manufacturing | 2024 |
| Integra Advisers Limited Liability Partnership | | 2009 |
| Integra Consulting UK Limited | Professional & scientific | 2008 |
| Integral Healthcare Ltd | Health & social care | 2013 |
| Integrate Families LLP | | 2019 |
| Integrated in Sensory Praxis Ltd | Administrative & support | 2010 |
| Integrated Lift Solutions Limited | Extraterritorial | 2015 |
| Integrated Projects Ltd | Construction | 2017 |
| Integrated Security Systems Group Limited | Administrative & support | 2011 |
| Integrity Accounting Services Ltd | Professional & scientific | 2020 |
| Intelepathic Ltd | Information & communication | 2023 |
| Intelligent Coatings (North) Ltd | Construction | 2023 |
| Intelligent Ground Response Mapping Limited | Information & communication | 2023 |
| Inter Co-Serve Ltd | Real estate | 2018 |
| Inter Homes North Ltd | Construction | 2017 |
| Interior Goods Direct Limited | Wholesale & retail | 2003 |
| Interiors UK Limited | Construction | 2004 |
| International Bearings Limited | Wholesale & retail | 2022 |
| International Fibres Group (Holdings) Limited | Professional & scientific | 1949 |
| International Fibres Group Limited | Professional & scientific | 2011 |
| International Graduate Programme Ltd | Professional & scientific | 2025 |
| Internis Pharmaceuticals Limited | Health & social care | 2010 |
| Interscope Export and Sales Ltd | Wholesale & retail | 2023 |
| Interstellar Topology UK Private Ltd | Wholesale & retail | 2026 |
| Intervo (UK) Ltd | Wholesale & retail | 2014 |
| Interweave Textiles Limited | Wholesale & retail | 2004 |
| Intext Installations Ltd | Construction | 2021 |
| Intizar Hussain Ltd | Transport & logistics | 2023 |
| Intouch Geospatial Services Ltd. | Information & communication | 2014 |
| Intravive Ltd | Health & social care | 2022 |
| Inverse Metric Ltd. | Professional & scientific | 2024 |
| Invest IT Ltd | Information & communication | 2019 |
| Invest IT Recruitment Services Ltd | Administrative & support | 2022 |
| Investment Property 67 Limited | Real estate | 2022 |
| Investment Property Advantage Ltd | Real estate | 2023 |
| Investnest Trading Ltd | Financial services | 2025 |
| Invex Media Ltd | Professional & scientific | 2025 |
| Invincible PVT Ltd | Wholesale & retail | 2024 |
| Invisible Limited | Hospitality | 1982 |
| Invoicedrop Ltd | Information & communication | 2014 |
| Inya Ltd | Information & communication | 2017 |
| Ipcs West Yorkshire Ltd | Professional & scientific | 2013 |
| Iphones Limited | Wholesale & retail | 2005 |
| IPU Consultancy Ltd | Information & communication | 1996 |
| IQA Services Ltd | Professional & scientific | 2019 |
| Iqbal Group Limited | Financial services | 2025 |
| Iqbal’S Cooperation Ltd | Transport & logistics | 2026 |
| IR Consultancy Ltd | Professional & scientific | 2016 |
| Ired Rentals Ltd | Arts & recreation | 2024 |
| Irem Mobile Catering Ltd | Hospitality | 2020 |
| Irentra Ltd | Information & communication | 2025 |
| Iridex Engineering Co. Limited | Wholesale & retail | 1963 |
| Irie Eats Ltd | Hospitality | 2025 |
| Irish Fiddler Ltd | Hospitality | 2026 |
| Iroko Community Alliance CIC | Professional & scientific | 2022 |
| Iron DAD Coaching Ltd | Other services | 2025 |
| Ironheart Cyber Ltd | Information & communication | 2023 |
| Irshad Holding Limited | Financial services | 2025 |
| Irus Ltd | Arts & recreation | 2013 |
| Iryt Limited | Arts & recreation | 2023 |
| ISA IT Consulting Ltd | Information & communication | 2010 |
| Isaa Healthcare Ltd | Health & social care | 2019 |
| Isaac James Associates Limited | Administrative & support | 2021 |
| Isaac Machinery Limited | Wholesale & retail | 2012 |