| I-Hawk Ltd | Manufacturing | 2017 |
| I.C.E. Electrical Services Ltd | Construction | 2011 |
| I.E. Freight Ltd | Transport & logistics | 2023 |
| I.T.S. Tools Limited | Real estate | 1976 |
| I2I Properties Limited | Real estate | 2021 |
| IA Repairs Ltd | Wholesale & retail | 2025 |
| IAC Lamtek Limited | Manufacturing | 2018 |
| Iain Maclean Consultancy Limited | Professional & scientific | 2013 |
| IAK Food (Newport) Ltd | Hospitality | 2022 |
| IAN Bartlett Transport Limited | Administrative & support | 2017 |
| IAN Hodges & Co (Hull) Limited | Real estate | 2013 |
| IAN Prosser Building Services Ltd | Construction | 2021 |
| IB Wood & Sons Limited | Arts & recreation | 2003 |
| Ibercus Biotek Ltd | Wholesale & retail | 2021 |
| Ibex Enterprises Ltd | Information & communication | 2026 |
| Ibex Heritage Ltd | Construction | 2026 |
| Ibile Foodstore Ltd | Wholesale & retail | 2024 |
| IBJ Properties Limited | Hospitality | 2007 |
| IBN Fragrances Ltd | Wholesale & retail | 2025 |
| IBN Imports Ltd | Wholesale & retail | 2025 |
| Ibraa Limited | Wholesale & retail | 2024 |
| Ibrah Ltd | Wholesale & retail | 2024 |
| IBRAHIM777 Cargo Worldwide Ltd | Transport & logistics | 2025 |
| Ibse Limited | Information & communication | 2013 |
| Ibtc Consultant Ltd | Professional & scientific | 2022 |
| IC Designs Ltd | Professional & scientific | 2009 |
| Icanfoster Ltd | Health & social care | 2019 |
| Ice Boba Limited | Manufacturing | 2023 |
| Ice Solar Trustee Limited | Professional & scientific | 2026 |
| ICF Builds UK Ltd | Construction | 2022 |
| ICF Holdings Limited | Financial services | 2019 |
| Ichiban Creative Ltd | Professional & scientific | 2019 |
| Icon & Co (Wales) Limited | Professional & scientific | 2009 |
| Icon Creative Design Ltd | Professional & scientific | 2000 |
| Icon Expo Limited | Arts & recreation | 2018 |
| Iconic Events Limited | Administrative & support | 2023 |
| ICP Electrical Services Limited | Construction | 2002 |
| ICP Newtech (UK) Ltd | Manufacturing | 2025 |
| IDC Engineering Limited | Manufacturing | 2025 |
| Ideal Fitness Limited | Arts & recreation | 2008 |
| Ideal M&E Ltd | Construction | 2016 |
| Ideal Marketing Solutions Limited | Administrative & support | 2015 |
| Idealoom Ltd | Professional & scientific | 2024 |
| Identified Health Care Limited | Health & social care | 2022 |
| Idesigntutorials UK Ltd | Education | 2023 |
| IDM Consultancy Ltd | Professional & scientific | 2019 |
| IDM Doors (Trustees) Limited | Financial services | 2025 |
| IDM Doors Limited | Manufacturing | 2005 |
| IDM Window Systems Limited | Manufacturing | 2012 |
| Idmax Limited | Professional & scientific | 2008 |
| Idol Fever Ltd | Wholesale & retail | 2024 |
| Idris Stables Limited | Agriculture & fishing | 2023 |
| IDU Holdings Ltd | Wholesale & retail | 2019 |
| Idyllic Weddings UK Ltd | Information & communication | 2023 |
| Iestyn C Boxing Ltd | Arts & recreation | 2025 |
| Ieuans Floor Fitting Business CYF | Construction | 2025 |
| Ifab Marine Services Ltd | Manufacturing | 2018 |
| Ifpl Group Limited | Financial services | 2006 |
| Ifracs Properties Ltd | Real estate | 2002 |
| Ifraim Ltd | Public administration | 2024 |
| Ifyizu Nwalie Ltd | Health & social care | 2022 |
| Igam Ogam Interiors Ltd | Professional & scientific | 2021 |
| Igbo Union of Wales CIC | Health & social care | 2025 |
| IGR (2024) Ltd | Wholesale & retail | 2024 |
| Iguys Refurb Ltd | Other services | 2019 |
| Ihcw & S Ltd | Wholesale & retail | 2018 |
| IJ Construction & Civil Engineering Limited | Construction | 2023 |
| IJE Shropshire Ltd | Real estate | 2011 |
| IJN Property Limited | Real estate | 2023 |
| IK Catering Ltd | Hospitality | 2021 |
| Ikon Sales Limited | Wholesale & retail | 2010 |
| Ikto Ltd | Information & communication | 2017 |
| Ilayda Landscapes Ltd | Other services | 2019 |
| ILM Projects Limited | Manufacturing | 2016 |
| Ilmeg Ltd | Real estate | 2024 |
| Ilvd Limited | Professional & scientific | 2018 |
| ILÉ Living Ltd | Wholesale & retail | 2025 |
| Image and Ocean Ltd | Administrative & support | 2021 |
| Imagelease U.K. Limited | Professional & scientific | 2003 |
| Imanigiftcompany Limited | Wholesale & retail | 2025 |
| Imbre Ltd | Education | 2019 |
| IMC Business Consultancy & Training Ltd | Professional & scientific | 2012 |
| Imcec Ltd | Construction | 2019 |
| Imcec Properties Ltd | Real estate | 2026 |
| Imdeq Limited | Administrative & support | 2008 |
| Imenex UK Limited | Information & communication | 1996 |
| Immigration Compliance Solutions for School Admission Ltd | Administrative & support | 2023 |
| Impact Innovation & Growth Services Limited | Professional & scientific | 1993 |
| Impact Innovation and Growth Services (Trading) Limited | Professional & scientific | 2021 |
| Impact Investment Foundation | Professional & scientific | 2018 |
| Imphouse Limited | Construction | 1985 |
| Imrs Hemingway Ltd | Professional & scientific | 2019 |
| IN IT Together Festival Ltd | Arts & recreation | 2025 |
| IN Rude Health Limited | Health & social care | 2018 |
| Inaya Limited | Hospitality | 2020 |
| Independence TT Limited | Information & communication | 2025 |
| Independent Arts | Health & social care | 1987 |
| Independent Carpet Supplies(I.W.)Limited | Wholesale & retail | 1970 |
| Independent Children Services (South Wales) Limited | Health & social care | 2001 |
| Independent Commercial Services (I.W) Ltd | Real estate | 2000 |