| Idam Builders Limited | Construction | 2024 |
| Idasons Limited | Real estate | 2018 |
| IDB Properties Limited | Real estate | 2004 |
| Idca Limited | Administrative & support | 2017 |
| IDD Advisory Ltd | Information & communication | 2020 |
| IDD Freight Ltd | Transport & logistics | 2018 |
| Iddylic Service Cardiff Limited | Manufacturing | 2025 |
| Idea Elite Limited | Professional & scientific | 2024 |
| Ideafood Ltd | Wholesale & retail | 2021 |
| Ideaforge Labs Ltd | Information & communication | 2025 |
| Ideal Care & Solutions Limited | Health & social care | 2025 |
| Ideal Decorators (NE) Limited | Wholesale & retail | 2004 |
| Ideal Eco Ltd | Administrative & support | 2018 |
| Ideal Flooring (Sussex) Limited | Wholesale & retail | 2016 |
| Ideal Gifts & Furniture Ltd | Wholesale & retail | 2019 |
| Ideal Locations Essex Limited | Real estate | 2019 |
| Idealhomeproducts Limited | Wholesale & retail | 2018 |
| Idealparts Shop Ltd | Administrative & support | 2025 |
| Idean Ltd | Administrative & support | 2025 |
| Ideas Extreme Limited | Administrative & support | 2025 |
| Ideas Forums Holdings Limited | Financial services | 2024 |
| Ideas Forums Ltd | Administrative & support | 2018 |
| Ideas Invest Ltd | Financial services | 2024 |
| Ideas X Limited | Wholesale & retail | 2025 |
| Ideation House Technologies Limited | Information & communication | 2022 |
| Idenfy Ltd | Administrative & support | 2022 |
| Identify Solutions Ltd | Administrative & support | 2018 |
| Identity Consultants Ltd | Information & communication | 2019 |
| Identity Labs ( Rugby ) Limited | Other services | 2019 |
| Identity Technology Limited | Information & communication | 2020 |
| Ideoa Services UK Ltd | Households | 2023 |
| IDH Contractors Ltd | Construction | 2022 |
| Idigitize Ltd | Professional & scientific | 2026 |
| Idiva Ltd | Wholesale & retail | 2015 |
| Idle Friday Ltd | Information & communication | 2019 |
| IDM Academy Ltd | Education | 2025 |
| Idmark Limited | Wholesale & retail | 1995 |
| Idomedia Ltd | Information & communication | 2017 |
| Idomotics Ltd | Manufacturing | 2013 |
| Idoophotobooths Limited | Professional & scientific | 2017 |
| Idooweddingcars Limited | Administrative & support | 2017 |
| IDP Education Limited | Information & communication | 2019 |
| IDP Traveling Ltd | Administrative & support | 2025 |
| IDP Worldwide Ltd | Wholesale & retail | 2025 |
| IDQ ML Ltd | Wholesale & retail | 2025 |
| Idsk Ltd | Hospitality | 2024 |
| Idwal Marine Services Limited | Transport & logistics | 2010 |
| Idwal Williams and Company Limited | Transport & logistics | 1948 |
| Idyfodol Ltd | Wholesale & retail | 2021 |
| IE IE Productions Limited | Information & communication | 2005 |
| IEA Marketing Business Ltd | Other services | 2018 |
| Iechyd DA @ CF14 CYF | Wholesale & retail | 2019 |
| Iechyd DA Cyfyngedig | Arts & recreation | 2005 |
| Iedufire Ltd | Construction | 2019 |
| IEI Brilliant Solutions Ltd | Administrative & support | 2019 |
| IEI Electrical & Emergency Ltd | Construction | 2025 |
| Ielectronics UK Ltd | Wholesale & retail | 2018 |
| IES AV Ltd | Construction | 2026 |
| Ieva(Uk) Ltd | Professional & scientific | 2019 |
| IEW Consulting Limited | Professional & scientific | 2022 |
| IF Building Service Ltd | Real estate | 2026 |
| IF Group Ltd | Manufacturing | 2017 |
| IF Lending (UK) II Limited | Financial services | 2017 |
| IF Lending (UK) Ltd | Financial services | 2016 |
| IFA Management Consultancy Ltd | Professional & scientific | 2019 |
| Ifeed Events Limited | Hospitality | 2024 |
| Ifinici Ltd | Professional & scientific | 2021 |
| IFP Consulting Limited | Administrative & support | 2007 |
| Ifrocare Co., Ltd | Manufacturing | 2025 |
| Ifruitz UK Ltd | Wholesale & retail | 2018 |
| IFS International Finance Solutions | Information & communication | 2021 |
| IFS Wealth Management Limited | Financial services | 2009 |
| Ifsl Ltd | Professional & scientific | 2018 |
| Ifsus Argan London Ltd | Wholesale & retail | 2019 |
| IG Border Limited | Hospitality | 2019 |
| IG Coatings Ltd | Manufacturing | 2019 |
| IG for Education Services Oxford Ltd | Education | 2017 |
| IG Plumbers Ltd | Construction | 2021 |
| Igaming News Limited | Information & communication | 2021 |
| Igbo Community of Wales CIC | Education | 2026 |
| Igcore Limited | Information & communication | 2025 |
| IGD Holdings Realisations LLP | | 2013 |
| IGF Ltd | Information & communication | 2023 |
| Ighile Music Group Limited | Information & communication | 2019 |
| Igneous Limited | Other services | 2018 |
| Ignissecure Systems Ltd | Administrative & support | 2025 |
| Ignite Events & Hire Cardiff Limited | Administrative & support | 2022 |
| Ignite Fintech Ltd | Professional & scientific | 2016 |
| Ignite Fire and Electrical Limited | Construction | 2019 |
| Ignite GAS Limited | Construction | 2017 |
| Ignite Hospitality Careers Ltd | Administrative & support | 2020 |
| Ignite Okami Ltd | Wholesale & retail | 2017 |
| Ignite Your Dreams Ltd | Information & communication | 2026 |
| IGNITE100 Investment Services Ltd | Financial services | 2019 |
| IGNITER100 UK Ltd | Information & communication | 2017 |
| Ignixion Ltd | Wholesale & retail | 2025 |
| Igo-Wego Bikes Limited | Administrative & support | 2016 |
| Igotfixed Limited | Manufacturing | 2020 |
| Igrow Education LP | | 2011 |
| Igwt Discounts Ltd | Wholesale & retail | 2026 |