| Iqra Investments Ltd | Real estate | 2012 |
| Iqra Solutions Ltd | Real estate | 2012 |
| Iqrah Education & Cultural Centre | Education | 2017 |
| Iqsys Limited | Information & communication | 2012 |
| Iqtrade Global Limited | Information & communication | 2024 |
| Iqualtech Limited | Wholesale & retail | 2015 |
| Iquila Ltd | Information & communication | 1996 |
| IR Cybersec Ltd | Administrative & support | 2023 |
| IR Foodservice Limited | Wholesale & retail | 2011 |
| IR Technologies House Ltd | Information & communication | 2025 |
| Iratafox@Height Ltd | Construction | 2018 |
| IRE Services Limited | Other services | 2004 |
| Ireland Secretarial Ltd | Professional & scientific | 2020 |
| Ireland Smurfitt Marine Share Co., Ltd | Mining & quarrying | 2026 |
| Iresure Limited | Professional & scientific | 2021 |
| IRG Group Limited | Other services | 2019 |
| Irianan Health Care Services Ltd | Health & social care | 2023 |
| Iridescent Bubbles Ltd | Wholesale & retail | 2023 |
| Iridescent Inspirations Ltd | Wholesale & retail | 2025 |
| Iridescentcapital Limited | Financial services | 2021 |
| Iridium Corporate Services Limited | Professional & scientific | 2002 |
| Irina House Ltd | Construction | 2024 |
| Irina Investment Limited | Hospitality | 2025 |
| Iris Care Group (Wales) Limited | Financial services | 2021 |
| Iris Care Group Midco 2 Limited | Financial services | 2024 |
| Iris Care Group Midco Limited | Financial services | 2020 |
| Iris Childcare Limited | Administrative & support | 2012 |
| Iris Construct Limited | Construction | 2019 |
| Iris Manufacturing Technology Limited | Wholesale & retail | 2021 |
| Iris Prize Outreach Limited | Information & communication | 2012 |
| Iris Property Group Limited | Real estate | 2017 |
| Iris Vision Ltd | Health & social care | 2026 |
| Irisdcleaningcompany Limited | Administrative & support | 2026 |
| Irix Export PC | | 2018 |
| IRM Consultancy Ltd | Professional & scientific | 2018 |
| Irom Properties Limited | Real estate | 1972 |
| Iron Attire Limited | Real estate | 2023 |
| Iron Command Ltd | Professional & scientific | 2023 |
| Iron Forge Software Ltd | Information & communication | 2025 |
| Iron HOG Logistics Ltd | Transport & logistics | 2020 |
| Iron Pear Ltd | Real estate | 2023 |
| Iron Protector Ltd | Wholesale & retail | 2024 |
| Iron Unique Limited | Manufacturing | 2020 |
| Iron Van Ltd | Transport & logistics | 2025 |
| Ironbridge Care Ltd | Health & social care | 2024 |
| Ironclad Contractors Limited | Construction | 2018 |
| Ironkey Homes Ltd | Real estate | 2026 |
| Ironvale Systems Ltd | Information & communication | 2025 |
| Ironveil Systems Ltd | Information & communication | 2025 |
| Ironwood Cloud Ltd | Information & communication | 2025 |
| Ironworks Industrial Ltd | Wholesale & retail | 2025 |
| Iruka Design Ltd | Professional & scientific | 2026 |
| Irvelis Ltd | Wholesale & retail | 2026 |
| Irvin M Social Care Ltd | Health & social care | 2024 |
| IS Warehouse Limited | Wholesale & retail | 2018 |
| ISA Barr FIN Ltd | Information & communication | 2025 |
| ISA Service & Administration Ltd | Financial services | 2024 |
| ISA Trades Ltd | Construction | 2024 |
| Isaac .N. Healthcare Services Ltd | Public administration | 2018 |
| Isaal Ltd | Information & communication | 2020 |
| Isabelle EVE Aesthetics Limited | Health & social care | 2023 |
| Isabelle Frank Limited | Construction | 2021 |
| Isabellla Ltd | Wholesale & retail | 2024 |
| Isadora Alliance PC | | 2017 |
| Isafen Ltd | Other services | 2025 |
| Isambard Capital LLP | | 2021 |
| Isambard Group Developments Ltd | Construction | 2021 |
| Isap Group Investments Ltd | Financial services | 2021 |
| Isaw Ltd | Wholesale & retail | 2024 |
| ISB Enterprises Ltd | Information & communication | 2024 |
| Isca Care Limited | Health & social care | 2021 |
| Isca Domos Limited | Real estate | 2018 |
| Isca Management Consulting Services Ltd | Professional & scientific | 2019 |
| Iscond Ltd | Wholesale & retail | 2020 |
| Isdan Global Ltd | Construction | 2022 |
| Isds Railway & Construction Services Limited | Administrative & support | 2014 |
| Isell Handel Ltd | Wholesale & retail | 2025 |
| Isesta Ltd | Wholesale & retail | 2020 |
| Isgrove Heating Limited | Construction | 2026 |
| Ishaq Ltd | Administrative & support | 2026 |
| Ishika Food & Wines Ltd | Wholesale & retail | 2019 |
| Ishopelectronics Ltd | Wholesale & retail | 2019 |
| Ishtar Holding Ltd | Manufacturing | 2021 |
| Ishvar UK Limited | Information & communication | 2015 |
| Isil Software Ltd | Information & communication | 2025 |
| Isis Printing Limited | Manufacturing | 2009 |
| Iskitoglu Ltd | Wholesale & retail | 2025 |
| Isla Grace Recruitment Solution Limited | Administrative & support | 2019 |
| Isla-Alexander Finance Limited | Financial services | 2024 |
| Isla-Alexander Property Experts Ltd | Real estate | 2022 |
| Isla-Alexander Sales Limited | Real estate | 2022 |
| Islamic Group Therapy Limited | Health & social care | 2025 |
| Islamic Relief & Development Association (Irada) | Health & social care | 2024 |
| Islamic World Economic Cooperation Organization Ltd | Financial services | 2019 |
| Islamy Voyage LLP | | 2022 |
| Island Lofts Management Limited | Households | 2004 |
| Island Pellet Stoves Limited | Manufacturing | 2009 |
| Island Sun Limited | | 1980 |
| Island View Properties (Hampshire) Limited | Other services | 2017 |
| Islandos Group Ltd | Extraterritorial | 2017 |