| Inspire Brickwork Company Ltd | Construction | 2025 |
| Inspire Design Consultancy Ltd | Professional & scientific | 2001 |
| Inspire School of Dance and Drama Limited | Arts & recreation | 2026 |
| Inspire to Independence (Property) Limited | Real estate | 2004 |
| Inspired Asset Group Ltd | Construction | 2026 |
| Inspired Bookings LLP | | 2013 |
| Inspired Internet Limited | Information & communication | 2006 |
| Inspired Investment Solutions Ltd | Financial services | 2016 |
| Inspired Joinery & Projects Ltd | Construction | 2025 |
| Inspired Structures Limited | Construction | 2012 |
| Inspired Youth Arts Ltd | Information & communication | 2005 |
| Inspired Youth Productions Ltd | Information & communication | 2007 |
| Inspiring Spaces Limited | Real estate | 2021 |
| Installation Maintenance Engineering Limited | Manufacturing | 2016 |
| Instant Grid Ltd | Energy | 2026 |
| Instant Trading Group Ltd | Wholesale & retail | 2020 |
| Instantdebit Limited | Wholesale & retail | 2024 |
| Instantdonate Limited | Information & communication | 2025 |
| Insted Limited | Real estate | 2023 |
| Instep Properties Ltd | Real estate | 2024 |
| Institute of Interim Management | Other services | 2002 |
| Institute of Money Advisers | Other services | 2005 |
| Institute of Physics and Engineering in Medicine | Information & communication | 1995 |
| Instyle Kitchens & Windows Ltd | Construction | 1999 |
| Insure IT Angels Ltd | Financial services | 2017 |
| Insvestigate Limited | Financial services | 2013 |
| Intager Limited | Administrative & support | 1997 |
| Intandem Communications Limited | Professional & scientific | 2010 |
| Intaroma Limited | Real estate | 2000 |
| Integracare Limited | Other services | 2003 |
| Integral Design & Media Limited | Information & communication | 2008 |
| Integrity Care Bridge Ltd | Health & social care | 2026 |
| Integrity Leadership Limited | Professional & scientific | 2019 |
| Intelligent Transport Services Limited | Construction | 2011 |
| Inten Media Ltd | Information & communication | 2021 |
| Inter County Lettings Limited | Real estate | 1988 |
| Inter Sports Management UK Ltd | Arts & recreation | 2022 |
| Inter-Nail Bulk Fixings Ltd | Wholesale & retail | 2006 |
| Inter-Nail Limited | Wholesale & retail | 2006 |
| Interact & Connect Ltd | Wholesale & retail | 2015 |
| Interactive Financial Solutions Limited | Financial services | 2010 |
| Interbeauty Cosmetics Limited | Wholesale & retail | 2026 |
| Interchange and Consort Hotels Limited | Hospitality | 1971 |
| Intercity Window Cleaning Ltd | Administrative & support | 2008 |
| Interim Staffing Ltd | Administrative & support | 2019 |
| Interlawn Ltd | Agriculture & fishing | 2024 |
| Internallyspeaking Ltd | Information & communication | 2025 |
| International Brands of York Ltd | Wholesale & retail | 2022 |
| International Curling Academy Limited | Arts & recreation | 2019 |
| International Elite Education Consultancy Ltd | Education | 2018 |
| International Finest Foods Limited | Wholesale & retail | 2017 |
| International Marine Survey Limited | Transport & logistics | 2013 |
| International Organisation for Medical Physics | Information & communication | 2017 |
| International Partners York Ltd | Education | 2017 |
| International Power Group Limited | Energy | 2025 |
| International Resources Limited | Financial services | 2019 |
| International Resourcing Solutions (Philippines) Limited | Professional & scientific | 2007 |
| International Skills UK Limited | Professional & scientific | 2015 |
| International Teachers Hub Ltd | Wholesale & retail | 2025 |
| Interpower Solutions Ltd | Construction | 2011 |
| Interview Ready Limited | Administrative & support | 2025 |
| Into a Dream Limited | Information & communication | 2025 |
| Intotal Developments Limited | Construction | 2017 |
| Intra Inns Limited | Hospitality | 1967 |
| Intrepid Findley Limited | Professional & scientific | 2022 |
| Intuition Impact Ltd | Professional & scientific | 2022 |
| Invent Partners Limited | Information & communication | 2008 |
| Inventory Management Solutions Limited | Real estate | 2006 |
| Invert the Pyramid Ltd | Real estate | 2020 |
| Invest 92 Ltd | Real estate | 2021 |
| Invested EPA Ltd | Real estate | 2017 |
| Investigate Inclusive Ltd | Professional & scientific | 2025 |
| Investing in Time Limited | Wholesale & retail | 2012 |
| Investors Independent Limited | Professional & scientific | 2018 |
| Invicta Knitting Mills Limited | Professional & scientific | 1939 |
| Invigorate Recruitment Limited | Administrative & support | 2006 |
| Invisions Music Ltd | Arts & recreation | 2019 |
| Inzingane | Financial services | 2024 |
| Inztec Composting Limited | Administrative & support | 2011 |
| Inztec Limited | Manufacturing | 2002 |
| Ioim Limited | Other services | 2002 |
| ION Dyson (Plumbing) Limited | Real estate | 1981 |
| ION Dyson Limited | Real estate | 1933 |
| Iona Management Services (Caledonia) Limited | Manufacturing | 2021 |
| IPA Holdings 1234 Limited | Real estate | 2025 |
| Ipem Enterprises Limited | Wholesale & retail | 1996 |
| Ipothica Limited | Financial services | 2018 |
| Ippuku Tea House Limited | Hospitality | 2017 |
| IPT Investments Limited | Real estate | 2006 |
| IQ Engineers Limited | Manufacturing | 2008 |
| IQ Property (Hull) Limited | Real estate | 2010 |
| IQE Holdings Limited | Financial services | 2024 |
| Ireland Landscapes Ltd | Professional & scientific | 2023 |
| Irene Atelier Ltd | Wholesale & retail | 2025 |
| Irepair and Iprotect Limited | Wholesale & retail | 2019 |
| Iris Graphics Ltd | Manufacturing | 2022 |
| Irregular Miniatures Limited | Manufacturing | 1986 |
| IRW Property Limited | Real estate | 2025 |
| Isfahim Properties Ltd | Real estate | 2026 |
| Ishy & Associates Ltd | Health & social care | 2026 |