| Imjha Engineering Limited | Professional & scientific | 2025 |
| IML Healthcare Group Limited | Construction | 2026 |
| Impel Consultants UK Ltd | Professional & scientific | 2022 |
| Impetus Automotive Limited | Administrative & support | 2000 |
| Improving Performance in Practice (Ipip) Limited | Administrative & support | 1991 |
| IN a Pigs EAR Cider Company Ltd | Wholesale & retail | 2021 |
| In-Tech Group Ltd | Professional & scientific | 2015 |
| Inayat Holdings Ltd | Real estate | 2020 |
| INBOUND7 Ltd | Information & communication | 2026 |
| Incat International PLC | Professional & scientific | 1989 |
| Independent Association of Prep Schools | Education | 2007 |
| Independent Freight Solutions Limited | Transport & logistics | 2004 |
| Industry Today Media Ltd | Information & communication | 2016 |
| Infiniwell UK Limited | Wholesale & retail | 2020 |
| Infiquity UK Limited | Information & communication | 2023 |
| Infobric Workforce UK Limited | Construction | 2014 |
| Infofx Property Limited | Real estate | 2017 |
| Informative Energy Limited | Information & communication | 2016 |
| Ingenia Industrial Design LLP | | 2015 |
| Inglefield Construction Ltd. | Construction | 2012 |
| Ingon Tarmac Limited | Construction | 2014 |
| Injury Claim Solutions Limited | Other services | 2008 |
| Inlnkdata Ltd | Information & communication | 2020 |
| Innovate Healthcare Services Limited | Health & social care | 2020 |
| Innovatus Safety Ltd | Administrative & support | 2012 |
| Innovatus Telecom Services Limited | Information & communication | 2023 |
| Inntonic MOR Ltd | Hospitality | 2025 |
| Inriver Ltd | Information & communication | 2016 |
| Inside Sport Consulting Limited | Professional & scientific | 2017 |
| Insight 2 Value Holdings Limited | Financial services | 2017 |
| Insight 2 Value Limited | Information & communication | 2011 |
| Insight Presentation Systems Limited | Information & communication | 1993 |
| Insightpsychotherapist.Com Ltd | Health & social care | 2020 |
| Insitebuilds Ltd | Construction | 2019 |
| Insperso Limited | Education | 2015 |
| Instrata Consulting Ltd | Information & communication | 2021 |
| Int-Air Ltd | Manufacturing | 2025 |
| Intaglio Investments Limited | Professional & scientific | 1964 |
| Integritas Holdings Limited | Financial services | 2024 |
| Integrity Magazine Ltd | Information & communication | 2020 |
| Integrity Scientific Ltd | Professional & scientific | 2007 |
| Intel Travel Ltd | Administrative & support | 2024 |
| Inteligent Telecoms Routing Ltd | Information & communication | 2025 |
| Intelligent Design Agency Limited | Hospitality | 2026 |
| Intelligent Dog Training Limited | Extraterritorial | 2020 |
| Intelligent OH Ltd | Professional & scientific | 2022 |
| Interactive Touch Technology Ltd | Information & communication | 2020 |
| Interactive Touch Technology North Ltd | Information & communication | 2026 |
| Interceptor Investments Limited | Financial services | 2026 |
| Interior Solutions GB Limited | Construction | 2007 |
| Interlogical Limited | Information & communication | 2001 |
| International Centre for Civic Innovation Limited | Administrative & support | 2016 |
| Intolec Limited | Construction | 2021 |
| Intouch Training Ltd | Information & communication | 2015 |
| Intrepid IP Limited | Professional & scientific | 2022 |
| Inuka Limited | Professional & scientific | 2014 |
| Inverid Limited | Information & communication | 2022 |
| Investment Consultancy Hub Ltd | Financial services | 2025 |
| Investrite Limited | Extraterritorial | 2013 |
| Invivo Consultancy Services Limited | Administrative & support | 2019 |
| Invoicenet Ltd | Administrative & support | 2021 |
| IO3T Ltd | Manufacturing | 2021 |
| IPC Energy Limited | Financial services | 2020 |
| Ipip Holdings Limited | Financial services | 2021 |
| IPR Evesham Limited | Real estate | 2023 |
| IPR Whisson Holdings Limited | Financial services | 2023 |
| Irvine Holdings Limited | Professional & scientific | 2007 |
| Isaac Property Lettings Ltd | Real estate | 2017 |
| Isochor Engines Limited | Professional & scientific | 2026 |
| Isun Holdings (UK) Ltd | Wholesale & retail | 2017 |
| It's a 10 Haircare Limited | Wholesale & retail | 2022 |
| It's Showtime Limited | Arts & recreation | 2014 |
| Itcss Limited | Information & communication | 2022 |
| Itrack Education Limited | Information & communication | 1993 |
| It’S Smart Ltd | Wholesale & retail | 2023 |
| Ivory Aesthetics Ltd | Other services | 2026 |
| Iwood Carpentry Ltd | Manufacturing | 2026 |
| Iworkout Ltd | Education | 2020 |
| Izen Engineering Limited | Manufacturing | 2020 |
| IZR Consulting Limited | Information & communication | 2014 |
| J & a Tax Limited | Professional & scientific | 2019 |
| J & G Product Management Ltd | Information & communication | 2017 |
| J & J Hyman Pharmacy Limited | Extraterritorial | 1998 |
| J & JS Limited | Wholesale & retail | 2006 |
| J & L Asbestos Removal Limited | Construction | 2006 |
| J & O Builders Ltd | Construction | 2021 |
| J & W J Ellis Limited | Administrative & support | 2013 |
| J Consultancy Limited | Administrative & support | 2007 |
| J M Osborne Rural & Sporting Ltd | Professional & scientific | 2020 |
| J M Partnership (QS) Limited | Professional & scientific | 2009 |
| J T Electrical Installation Services Limited | Construction | 2021 |
| J&P Dhillon Properties Ltd | Real estate | 2020 |
| J&P Food Corp Ltd | Hospitality | 2025 |
| J. & N. Rymer Limited | Agriculture & fishing | 2004 |
| J. Farmer Services Ltd | Health & social care | 2023 |
| J. P. Plumbing and GAS Heating Limited | Construction | 2012 |
| J.A.S. Estates Ltd | Real estate | 2017 |
| J.C.Lockwood Construction Limited | Construction | 2019 |
| J.F. Buckingham Limited | Real estate | 1941 |
| J.J. Gallagher Limited | Real estate | 2017 |