| HYT UK Ltd | Wholesale & retail | 2020 |
| I H Building Ltd | Construction | 2020 |
| I Smashed IT Productions Ltd | Arts & recreation | 2016 |
| I-River Ltd | Administrative & support | 2009 |
| I.C. Enterprises Limited | Professional & scientific | 2003 |
| I.D. Hughes & Associates Limited | Information & communication | 2003 |
| I.E. Informal Education Ltd | Education | 2006 |
| I3 Creative Ltd | Information & communication | 2015 |
| IAD Business Ltd | Transport & logistics | 2025 |
| Iamsilver Limited | Information & communication | 2016 |
| IAN Stott Personal Training Limited | Health & social care | 2006 |
| IAN Tyers Property Limited | Real estate | 2018 |
| IBB Consultancy Limited | Professional & scientific | 2023 |
| Ibzamu Ltd | Information & communication | 2018 |
| IC Realtime UK Limited | Administrative & support | 2011 |
| Icarus Luxe Ltd | Real estate | 2020 |
| Icedog Design Limited | Professional & scientific | 2005 |
| Icle Fairy Ltd | Health & social care | 2022 |
| Icoy Ltd | Wholesale & retail | 2023 |
| ID Advance Designs Limited | Wholesale & retail | 2024 |
| ID Health Limited | Health & social care | 2023 |
| Iddy Design Ltd | Professional & scientific | 2021 |
| Ideacake Ltd | Professional & scientific | 2017 |
| Ideal Business Consulting Limited | Professional & scientific | 2024 |
| Ideal Roofing and Building Ltd | Construction | 2019 |
| Ideal Surrey Ltd | Administrative & support | 2020 |
| Ideals Today Limited | Wholesale & retail | 2026 |
| Identity Protection Limited | Information & communication | 2017 |
| Idwr Ltd | Administrative & support | 1998 |
| IF YOU Limited | Professional & scientific | 2023 |
| Ifix Gadgets Limited | Wholesale & retail | 2016 |
| IG10 Ltd | Information & communication | 1997 |
| IGB Property Services Limited | Construction | 2025 |
| Igenomix UK Ltd | Professional & scientific | 2017 |
| Ignite Medical Consulting Limited | Professional & scientific | 2024 |
| IHA Consulting Limited | Professional & scientific | 2012 |
| IHS Africa (UK) Limited | Information & communication | 2013 |
| IJK Agri Ltd | Professional & scientific | 2023 |
| Ikigo Solutions Ltd | Professional & scientific | 2025 |
| Ikog Ltd | Financial services | 2024 |
| Ikon Menswear Ltd | Wholesale & retail | 2006 |
| Illusion Art Beauty Ltd | Other services | 2020 |
| Ilumiti LLP | | 2013 |
| Ilutra Systems Ltd | Information & communication | 2000 |
| IMADEIT3D Ltd | Manufacturing | 2024 |
| Image Automotive Holdings Limited | Wholesale & retail | 2012 |
| Image Skincare UK Limited | Other services | 2016 |
| Imagineer Systems Ltd | Information & communication | 2002 |
| Imanraheela Ltd | Health & social care | 2022 |
| Imba DZA Mudiwa Ltd | Real estate | 2024 |
| Imberhorne Investments Limited | Real estate | 1959 |
| Immersive Industry Experiences Limited | Information & communication | 2024 |
| IMMIGRATION2OZ.COM Limited | Professional & scientific | 2005 |
| Imogen Gaunt Consultancy Ltd | Professional & scientific | 2022 |
| Impact Exhibitions & Events Limited | Administrative & support | 2007 |
| Impact for Good Limited | Professional & scientific | 2022 |
| Impact Skills Solutions Ltd | Professional & scientific | 2022 |
| Impact Training Services Ltd. | Information & communication | 2016 |
| Imperial G-Ford Ltd | Construction | 2025 |
| Imperial Urology Limited | Health & social care | 2017 |
| Imperium Consulting Limited | Professional & scientific | 2015 |
| IN House Social Ltd | Education | 2020 |
| IN the City Events Limited | Arts & recreation | 2025 |
| IN2DETAIL Ltd | Information & communication | 2009 |
| Inchstone Limited | Information & communication | 2026 |
| Inclusion Psychologists Limited | Other services | 2018 |
| Inclusive Education Trust | Education | 2021 |
| Inclusive Swim School Ltd | Education | 2023 |
| Incofood Corporation Limited | Professional & scientific | 1985 |
| Increase Altitude Limited | Professional & scientific | 2019 |
| Incus Technologies Limited | Information & communication | 2014 |
| Indabacad Ltd | Information & communication | 2013 |
| Independent Dyslexia Services Ltd | Professional & scientific | 2014 |
| Independent Power Projects Limited | Professional & scientific | 2021 |
| Independent Power Projects Mining Limited | Professional & scientific | 2025 |
| Indigo Investment Management Limited | Real estate | 2023 |
| Indigo Iris Limited | Professional & scientific | 2015 |
| Industria International Limited | Extraterritorial | 2000 |
| Industrication Inc. Limited | Administrative & support | 2006 |
| Infinitus Hub Services Ltd | Administrative & support | 2024 |
| Infinity Line Media Ltd | Professional & scientific | 2025 |
| Infinity Mind and Body Ltd | Arts & recreation | 2024 |
| Inforex DOT EU DOT COM Limited | Information & communication | 2011 |
| Information Services Group Europe Limited | Administrative & support | 1980 |
| Information Software Limited | Information & communication | 1982 |
| Informed Outcomes Limited | Professional & scientific | 2020 |
| Infovista Ltd. | Wholesale & retail | 1996 |
| Infrastructure Matters Holdings Limited | Financial services | 2023 |
| Ingenious Technical Solutions Ltd | Information & communication | 2022 |
| Inglewood Consulting Ltd | Professional & scientific | 2025 |
| Inglorious Monkey Ltd | Information & communication | 2025 |
| Ingo Health Ltd | Professional & scientific | 2020 |
| Inigmis Ltd | Information & communication | 2012 |
| Injury Solutions Limited | Extraterritorial | 2006 |
| INK Academy Limited | Education | 2016 |
| Inkrate Ltd | Manufacturing | 2022 |
| Inkria Capital Ltd | Financial services | 2026 |
| Inner Game Consulting Ltd | Professional & scientific | 2025 |
| Innert Security Ltd | Construction | 2023 |
| Innomatters Ltd | Administrative & support | 2021 |