| Interguide LS Limited | Real estate | 2011 |
| Interim BED Service Limited | Transport & logistics | 2008 |
| Interior Home Solutions Essex Limited | Construction | 2024 |
| Interior Home Solutions Limited | Construction | 2018 |
| Interior Workshops (London) Limited | Manufacturing | 1976 |
| Interiors in London Ltd | Manufacturing | 2020 |
| Interlude Digital Limited | Professional & scientific | 2020 |
| Intermeal Ltd | Financial services | 2026 |
| International BI Solutions Ltd | Information & communication | 2023 |
| International Colours Import & Export Limited | Wholesale & retail | 2010 |
| International Food Croydon Ltd | Wholesale & retail | 2020 |
| International Meat Co Ltd | Wholesale & retail | 2025 |
| International Paneurhythmy Academy "Beinsa Douno" Community Interest Company | Health & social care | 2020 |
| International Publishing House "Beinsa Douno" CIC | Health & social care | 2021 |
| International Sales Consultancy Limited | Wholesale & retail | 2016 |
| International Service Group & Partners Finance Limited | Professional & scientific | 2025 |
| International Service Group & Partners Ltd | Construction | 2025 |
| International Television Channel Limited | Information & communication | 2004 |
| International Youth Sports Centre Ltd | Education | 2024 |
| Intersoftkk Limited | Information & communication | 2023 |
| Interweb Systems Limited | Professional & scientific | 1994 |
| Interwebse Ltd | Information & communication | 2019 |
| Inthesky Limited | Households | 2019 |
| Intimate Kreations Ltd | Other services | 2023 |
| Intraview Limited | Real estate | 2014 |
| Intrd Ltd | Wholesale & retail | 2023 |
| Intro-Fast Limited | Administrative & support | 2016 |
| Introscope Limited | Professional & scientific | 2024 |
| Intueducation Limited | Education | 2021 |
| Intuitive Media Limited | Professional & scientific | 1997 |
| Inventus Tech Ltd | Health & social care | 2024 |
| Invermay Court Residents Limited | Households | 1996 |
| Investa Properties Inc Ltd | Real estate | 2024 |
| Investex Capital London Ltd | Professional & scientific | 2023 |
| Investinx Ltd | Other services | 2015 |
| Investment Group London Limited | Real estate | 2024 |
| Investsimply Group UK Limited | Administrative & support | 2024 |
| Invexe Limited | Administrative & support | 2009 |
| Invicta 24 Plus Limited | Administrative & support | 2014 |
| Invictus Martial Arts Academy Ltd | Arts & recreation | 2022 |
| Invigorate Education Ltd | Education | 2020 |
| Invira Ltd | Information & communication | 2025 |
| Invoke-Script Limited | Information & communication | 2019 |
| Invromight Group Ltd. | Manufacturing | 2026 |
| ION++ Ltd | Information & communication | 2013 |
| Ionian Plumbing & Heating Limited | Construction | 2026 |
| IOW Care Homes Limited | Administrative & support | 1993 |
| IP Wise Limited | Information & communication | 2002 |
| IP50 Ltd | Real estate | 2024 |
| IP70 Ltd | Real estate | 2025 |
| Ipag Ltd | Wholesale & retail | 2024 |
| IPC Consultants Ltd | Administrative & support | 2011 |
| Ipcm Cathedral DOS Milagres Limited | Other services | 2026 |
| Ipcn Limited | Professional & scientific | 2025 |
| Iphenom Ltd | Wholesale & retail | 2019 |
| Ippney Ltd | Wholesale & retail | 2026 |
| Ipropertyuk Ltd | Real estate | 2015 |
| IQ Property Cleaning Ltd | Administrative & support | 2025 |
| IQI (UK) Limited | Administrative & support | 2014 |
| Iraa Infotech Ltd | Administrative & support | 2014 |
| Iraqi Shawarma Ltd | Hospitality | 2025 |
| Ireké Juice Limited | Wholesale & retail | 2023 |
| Iridium Trading Ltd | Wholesale & retail | 2017 |
| Irina Sitnikova Consulting Ltd | Information & communication | 2025 |
| Iris Admin Solutions Ltd | Professional & scientific | 2021 |
| IRO Sushi Ltd | Hospitality | 2021 |
| Iron Castle Limited | Professional & scientific | 2014 |
| Ironclad Masonry Co Ltd | Manufacturing | 2025 |
| Ironshield Security Services Ltd | Administrative & support | 2020 |
| Irwin Building Services Limited | Construction | 2014 |
| IRX Solutions Limited | Health & social care | 2010 |
| IS1 Limited | Real estate | 2026 |
| Isaac ADU Limited | Construction | 2016 |
| Isaac Jacob Overseas UK Ltd | Construction | 2022 |
| Isaze Holdings Ltd | Real estate | 2021 |
| Isbiz Payroll Services Ltd | Professional & scientific | 2016 |
| ISD Real Estate Limited | Real estate | 2024 |
| Isecure Homes Ltd | Administrative & support | 2015 |
| Iselin Art Advisory Limited | Wholesale & retail | 2014 |
| Isfck Ltd | Wholesale & retail | 2024 |
| Ishari Limited | Real estate | 2017 |
| Ishirosoft Limited | Information & communication | 1998 |
| Ishraqnsons Limited | Wholesale & retail | 2026 |
| Ishtanay Solutions Limited | Professional & scientific | 2025 |
| Isio Wealth Planning Limited | Financial services | 2006 |
| Isiobi Ndigbo UK and Ireland Ltd | Wholesale & retail | 2026 |
| Isis Property Management and Lettings Limited | Real estate | 2002 |
| Islam Grocery Ltd | Wholesale & retail | 2020 |
| Island Express Limited | Households | 1988 |
| Island HR Solutions Ltd | Information & communication | 2024 |
| ISM Future Ltd | Financial services | 2025 |
| Ismail Khan Consulting Ltd | Extraterritorial | 2024 |
| Ismash Clinic Limited | Wholesale & retail | 2016 |
| Isola Solutions Ltd | Other services | 2023 |
| Isolar Records C.I.C. | Information & communication | 2022 |
| Isolpol Ltd | Wholesale & retail | 2019 |
| Isoource Limited | Wholesale & retail | 2019 |
| Isra International Ltd | Administrative & support | 2024 |
| ISS (GB) Limited | Information & communication | 2013 |
| ISS Real Estate Limited | Real estate | 2025 |