| Icanique Research Limited | Professional & scientific | 2010 |
| Icanique Technology Limited | Manufacturing | 2010 |
| ICARE4HEALTH Ltd | Public administration | 2023 |
| Icars Automotive Ltd | Wholesale & retail | 2019 |
| Icarus (Bristol) Ltd | Construction | 2014 |
| Icastrotechnology LLP | | 2022 |
| ICB Security Ltd | Administrative & support | 2025 |
| ICC Building Preservation Limited | | 1973 |
| Ice and Fire SKI and Snowboard Holidays Ltd | Hospitality | 2010 |
| Ice Fabric Services Limited | Manufacturing | 2011 |
| Ice Mill Ltd | Manufacturing | 2021 |
| Icebreaker Audio Limited | Information & communication | 2015 |
| Icehouse Systems Ltd | Information & communication | 2021 |
| Icertis Group Ltd | Information & communication | 2017 |
| Icescape Limited | Administrative & support | 2014 |
| Iceway Group Limited | Professional & scientific | 2025 |
| ICF Manufacturing (Holdings) Limited | Manufacturing | 2025 |
| ICF Manufacturing Limited | Construction | 2025 |
| Ichigo Health Ltd | Health & social care | 2023 |
| Ichrome Ltd | Information & communication | 2009 |
| ICL Construction Ltd | Construction | 2019 |
| Icms Holdings Ltd | Real estate | 2026 |
| ICN Business Limited | Professional & scientific | 2003 |
| Icoc Limited | Wholesale & retail | 2020 |
| Icomsoft Limited | Information & communication | 1988 |
| Icon Construction Services Limited | Construction | 1993 |
| Icon Corporate Finance Limited | Financial services | 1999 |
| Icon Films Limited | Information & communication | 1995 |
| Iconectiv UK Limited | Information & communication | 1984 |
| Iconic Property Rental Ltd | Extraterritorial | 2024 |
| Iconic Simulation Ltd | Professional & scientific | 2022 |
| Iconist Media Ltd | Information & communication | 2011 |
| Icrict | Professional & scientific | 2024 |
| ICS Hire Limited | Administrative & support | 2011 |
| ICT Auto Electrical Limited | Wholesale & retail | 2022 |
| Icti Care (Europe) Limited | Professional & scientific | 2015 |
| ICW Risk Services Limited | Financial services | 2007 |
| ICY EWE Optical Solutions Ltd | Professional & scientific | 2024 |
| ICY SIM Ltd | Information & communication | 2025 |
| ID Skin Surgery Limited | Health & social care | 2023 |
| ID Spirits Limited | Wholesale & retail | 2022 |
| Id-Laboratory Ltd | Information & communication | 2025 |
| IDA Innovations Limited | Construction | 2016 |
| IDA Lifestyle Ltd | Wholesale & retail | 2019 |
| Idalina Care Limited | Health & social care | 2020 |
| Idas Properties Ltd | Real estate | 2025 |
| Iddparts Limited | Manufacturing | 2015 |
| Ideabeams Ltd | Wholesale & retail | 2018 |
| Ideal Campervan Ltd | Manufacturing | 2022 |
| Ideal Delivery 8 Limited | Transport & logistics | 2022 |
| Ideal Engineering Consultants Limited | Construction | 2025 |
| Ideal Goods Ltd | Wholesale & retail | 2022 |
| Ideal Lets Ltd | Real estate | 2020 |
| Ideal Mortgage Advisers LLP | | 2019 |
| Ideal Security Services Ltd | Administrative & support | 2022 |
| Ideal Services (Bristol) Ltd | Administrative & support | 2018 |
| Idealsoft Limited | Information & communication | 2007 |
| Ideanco UK Ltd | Professional & scientific | 2019 |
| Ideas ETC Limited | Information & communication | 2002 |
| Ideas Foundation | Professional & scientific | 2001 |
| Ideas Fusion Ltd | Information & communication | 2018 |
| Ideas Made Visual Limited | Arts & recreation | 2025 |
| Ideasquares Worldwide Ltd | Administrative & support | 2013 |
| Idec Facilities Management Ltd | Construction | 2021 |
| Idem Capital Ltd | Financial services | 2022 |
| Idem ET Diversum Holdings Ltd | Financial services | 2025 |
| Identimark Ltd | Other services | 1991 |
| Identity Hair and Beauty Limited | Other services | 2016 |
| Idimitrov Ltd | Transport & logistics | 2025 |
| Iding Trading Ltd | Wholesale & retail | 2024 |
| Idiomatic Translations Limited | Administrative & support | 2006 |
| Idlemachines Ltd | Education | 2026 |
| Idoz Games Ltd | Information & communication | 2021 |
| Idpe | Education | 1999 |
| Idriss Integrated Solutions Ltd | Information & communication | 2026 |
| Idro Barber Shop Limited | Other services | 2024 |
| IE8 Limited | Professional & scientific | 2018 |
| IES Digital Systems PLC | Manufacturing | 2000 |
| IF NOT NOW Digital Ltd | Professional & scientific | 2016 |
| Ifach Ltd | Real estate | 2026 |
| Ifamax Holdings Limited | Financial services | 2025 |
| Ifamax Limited | Financial services | 2004 |
| Ifave Care Response Ltd | Health & social care | 2022 |
| Ifeys Care Limited | Health & social care | 2024 |
| IFG Investco Limited | Extraterritorial | 2020 |
| Ifind Recruitment Ltd | Administrative & support | 2019 |
| Ifixx Electricals Ltd | Other services | 2020 |
| Ifly Design Ltd | Construction | 2022 |
| Iform Education Ltd. | Education | 2015 |
| IFS Global Investments Limited | Professional & scientific | 2011 |
| Igloo Consulting Ltd | Professional & scientific | 2023 |
| Igloo Domestics Limited | Administrative & support | 2018 |
| Ignis Assured Construction Limited | Construction | 2022 |
| Ignis Holdings Ltd | Real estate | 2025 |
| Ignis Innovations Ltd | Professional & scientific | 2024 |
| Ignisiq Ltd | Information & communication | 2025 |
| Ignite Digital Search Limited | Administrative & support | 2014 |
| Ignite Incentives Holdings Limited | Manufacturing | 2013 |
| Ignite Incentives Limited | Manufacturing | 2006 |
| Ignite Media Ltd | Information & communication | 2025 |