| Invest Money Tree Ltd | Real estate | 2022 |
| Invest West Ltd | Other services | 2018 |
| Investai Limited | Information & communication | 2024 |
| Investay Limited | Real estate | 2017 |
| Investicorp Ltd | Construction | 2016 |
| Investment (Paragon) Limited | Financial services | 2013 |
| Investment Property Number 1 Ltd | Real estate | 2019 |
| Investments Corporation Ltd | Real estate | 2022 |
| Investors in Health Limited | Professional & scientific | 2003 |
| Investors in the Community Group Limited | Administrative & support | 2006 |
| Investors in Veterans Ltd | Professional & scientific | 2016 |
| Invexor Ltd | Wholesale & retail | 2026 |
| Invia (Bristol) Limited | Construction | 2021 |
| Invicta Audio Ltd | Wholesale & retail | 2020 |
| Invicta Cleaning Services Ltd | Administrative & support | 2021 |
| Invicta Harbourside Management Limited | Households | 2012 |
| Invicto Tech Ltd | Manufacturing | 2020 |
| Invictus Business Services Limited | Construction | 2014 |
| Invictus Products Ltd | Wholesale & retail | 2010 |
| Invictus Professional Carpet, RUG & Upholstery Cleaning Ltd | Administrative & support | 2020 |
| Invictus Property Management and Developers Ltd | Real estate | 2022 |
| Invisible Army Community Interest Company | Arts & recreation | 2023 |
| Invisible Studio Creative Limited | Professional & scientific | 2019 |
| Invisible Visible CIC | Arts & recreation | 2024 |
| Invisible Window Cleaning Limited | Administrative & support | 2023 |
| Invisiglaze Limited | Extraterritorial | 2022 |
| Involving Residents in Solutions Ltd | Education | 2000 |
| Invro Limited | Manufacturing | 2003 |
| Inwel Property Services Ltd | Real estate | 2018 |
| Inye CIC | Health & social care | 2010 |
| Inzpire Group Limited | Professional & scientific | 2013 |
| Inzu Limited | Information & communication | 2016 |
| IO Associates Limited | Administrative & support | 2015 |
| IO Creative Ltd | Professional & scientific | 2024 |
| IO Plant Ltd | Wholesale & retail | 2000 |
| IO Property Invest Limited | Real estate | 2024 |
| Ioannis K Limited | Health & social care | 2013 |
| Ioch Ltd | Construction | 2025 |
| IOD Scientific Services Ltd | Professional & scientific | 2019 |
| Iolaire Consulting Limited | Professional & scientific | 2012 |
| Iomi Solutions Limited | Information & communication | 2007 |
| ION Acoustics Limited | Professional & scientific | 2006 |
| ION Controls Ltd | Professional & scientific | 2021 |
| ION Fire and Security Ltd | Administrative & support | 2023 |
| Ion-Ess Limited | Manufacturing | 2015 |
| Ionel Mechanic Limited | Water & waste | 2022 |
| Ionic Builds Ltd | Construction | 2021 |
| Ionix Performance Ltd | Wholesale & retail | 2026 |
| Ionut Cleanar Ltd | Administrative & support | 2022 |
| Ionut Dogaru Ltd | Transport & logistics | 2017 |
| IOP Educational Publishing Limited | Extraterritorial | 2001 |
| IOP Publishing Limited | Information & communication | 1949 |
| Iosis Clinic Limited | Health & social care | 2007 |
| IOT Delivery Ltd | Information & communication | 2018 |
| Iota Bristol Limited | Wholesale & retail | 2014 |
| Iotix Ltd | Information & communication | 2011 |
| Iova Ltd | Wholesale & retail | 2019 |
| Iownthat Ltd | Information & communication | 2026 |
| Ioxford Ltd | Other services | 2023 |
| IP Marine Limited | Information & communication | 2011 |
| IP People Ltd | Administrative & support | 2023 |
| IP2MEDIA Limited | Information & communication | 2018 |
| Ipension Limited | Financial services | 2007 |
| Iperfect Ltd. | Professional & scientific | 2011 |
| Ipex Commercial Management Limited | Administrative & support | 2009 |
| Iphone Srvices Ltd | Wholesale & retail | 2025 |
| IPK Investment Ltd | Real estate | 2025 |
| Ipower Electrical Contractors Limited | Construction | 2017 |
| Iprinciples Limited | Information & communication | 2003 |
| Ipromote Gigs Limited | Arts & recreation | 2013 |
| Ipsum Allied Ltd | Construction | 2019 |
| Ipsum Opus Limited | Manufacturing | 2019 |
| IPV Performance Management Ltd | Professional & scientific | 2008 |
| IQ Professional Services Limited | Professional & scientific | 2022 |
| Iqbal Enterprises Ltd | Real estate | 2020 |
| IQI Recruit Ltd | Professional & scientific | 2017 |
| IQM U.K. Ltd | Information & communication | 2026 |
| Iraci Property Management Limited | Real estate | 2012 |
| Iram Housing Ltd | Real estate | 2025 |
| Iravath Foods Ltd | Wholesale & retail | 2023 |
| IRB Marketing Solutions Ltd | Professional & scientific | 2024 |
| Irena Bess Limited | Energy | 2022 |
| Irena Dental LAB Limited | Health & social care | 2025 |
| Irene's Kitchen Limited | Hospitality | 2024 |
| Irenos Ltd | Wholesale & retail | 2022 |
| Irfanjaidipk Ltd | Wholesale & retail | 2025 |
| Irie Inns Ltd | Hospitality | 2013 |
| Iris Field Ltd | Extraterritorial | 2008 |
| Iris Health Solutions Limited | Health & social care | 2019 |
| Irish Hospitality Ltd | Hospitality | 2024 |
| Irisi | Health & social care | 2017 |
| Irismob Ltd | Information & communication | 2019 |
| IRM Mobility Limited | Health & social care | 2000 |
| Iroid Technologies UK Ltd | Information & communication | 2023 |
| Iroko Management Limited | Professional & scientific | 2019 |
| Iron Fury Limited | Wholesale & retail | 2026 |
| Iron Oak Gymnastics Limited | Education | 2026 |
| Iron-Lake Consulting Ltd | Information & communication | 2024 |
| Ironamber Limited | Construction | 1982 |
| Ironbridge Partners Limited | Administrative & support | 2022 |