| IAN Davies Demolition Limited | Administrative & support | 1998 |
| IAN Davies Investments Limited | Construction | 2020 |
| IAN Davies Plant & SON Ltd | Financial services | 2022 |
| IAN Davies Plant Limited | Construction | 1996 |
| IAN Hearle Limited | Construction | 2007 |
| IAN Jones Plastering Limited | Construction | 2019 |
| IAN M Bain Ltd | Professional & scientific | 2018 |
| IAX Consulting Limited | Extraterritorial | 2013 |
| IB Locum Services Limited | Wholesale & retail | 2016 |
| Iberians & Latin Americans in Wales Ila-Wales CIC | Education | 2022 |
| Ibotta Contracting Ltd | Other services | 2022 |
| Ibronatron Limited | Information & communication | 2012 |
| IBT Locums Ltd | Health & social care | 2022 |
| Ice 14 Limited | Professional & scientific | 2013 |
| Ice Property Management (Swansea) Ltd | Real estate | 2019 |
| ICJ Ltd | Transport & logistics | 2021 |
| Ickle Bubba Limited | Manufacturing | 2013 |
| Icna Investments Limited | Real estate | 2026 |
| ICO Wales Tournaments Limited | Arts & recreation | 2024 |
| Icon Elite Sports Travel Ltd | Other services | 2019 |
| ICS Capital Ltd | Real estate | 2024 |
| Icteria Limited | Professional & scientific | 1982 |
| Icwtch Healthcare Limited | Administrative & support | 2023 |
| Ideal Engineering & Contractors Ltd | Manufacturing | 2026 |
| Ideal Events Ltd | Administrative & support | 2025 |
| Ideal Works Ltd | Construction | 2013 |
| Ideas & Inks Limited | Arts & recreation | 2021 |
| IDH Construction Ltd | Construction | 2026 |
| IDL Scaffolding Ltd | Construction | 2013 |
| Iestyn Crocker Property Ltd | Hospitality | 2025 |
| Iestyn Griffiths Music Limited | Information & communication | 2024 |
| Ifan Rhys Ltd | Financial services | 2023 |
| IFG Developments Ltd | Households | 2012 |
| Iforma Ltd | Construction | 2026 |
| Igloo Wellness Centre Limited | Health & social care | 2025 |
| Iglw Ltd | Information & communication | 2024 |
| Ignite Your Power C.I.C. | Health & social care | 2024 |
| IGX2 Enterprises Limited | Professional & scientific | 2020 |
| Ihero Marketing & Solutions Limited | Professional & scientific | 2025 |
| IHS Homes Limited | Real estate | 2023 |
| IIP Systems Limited | Information & communication | 1998 |
| Ikos Development Grwp Ltd | Real estate | 2022 |
| Illtyd Thomas & Sons (Haulage) Limited | | 1971 |
| Illtyd Thomas (Medical) Ltd | Education | 2019 |
| Illumination Projects Ltd | Information & communication | 2014 |
| Illusions Events Live Limited | Arts & recreation | 2015 |
| ILM Hub Ltd | Information & communication | 2021 |
| Iloveflola Ltd | Manufacturing | 2018 |
| Imadca Ltd | Other services | 2025 |
| Imagicloud Ltd | Information & communication | 2019 |
| Imagine Photography Ltd | Professional & scientific | 2025 |
| Imagitech (Trustee) EOT Ltd | Professional & scientific | 2023 |
| Imagitech Consulting Limited | Information & communication | 2010 |
| Imagitech Limited | Information & communication | 1995 |
| Imco (UK) Limited Partnership | | 1998 |
| Imga Limited | Real estate | 2024 |
| Imifa Ltd | Hospitality | 2021 |
| Immix Software Limited | Information & communication | 1999 |
| Immobiliare GL Limited | Construction | 2021 |
| Immyaz Groups Limited | Hospitality | 2026 |
| Impact Learning & Data Solutions Limited | Education | 2005 |
| Impact School Improvement Limited | Education | 2015 |
| Imperial Desserts Ltd | Wholesale & retail | 2024 |
| Imperial Swan Ltd | Hospitality | 2026 |
| Imperial Tech Limited | Wholesale & retail | 2018 |
| Imperium Cost Consultants Limited | Professional & scientific | 2020 |
| Imperium Group Swansea Ltd | Professional & scientific | 2026 |
| Imperium Trading Group Ltd | Financial services | 2026 |
| Impervious Ltd | Wholesale & retail | 2019 |
| Impgrove Limited | Manufacturing | 1981 |
| Impressiveu Couture Ltd | Health & social care | 2025 |
| Imprexels Limited | Information & communication | 2018 |
| IN OUR Element Organisation | Education | 2015 |
| IN the Pipeline (South East) Ltd | Construction | 2021 |
| Incare Limited | Administrative & support | 2025 |
| Inclyne Ltd | Real estate | 1976 |
| Incomfort Ltd | Real estate | 2022 |
| Incroft Ltd | Households | 2024 |
| Independence UK Limited | Construction | 2008 |
| Independent Paint Supplies Ltd | Wholesale & retail | 2019 |
| Indian Cottage Swansea Ltd | Hospitality | 2017 |
| Indian Curry 2026 Ltd | Hospitality | 2026 |
| Indianopolis Limited | Hospitality | 2017 |
| Indigo Events and Occasions Ltd | Hospitality | 2022 |
| Indigo Events Limited | Administrative & support | 2006 |
| Indigo Rises Limited | Construction | 2018 |
| Industrial Cryogenics Limited | Professional & scientific | 2025 |
| Industrial Electrical Solutions Ltd | Construction | 2013 |
| Industrial Inspection Ltd | Construction | 2023 |
| Industrial Spraywash Ltd | Wholesale & retail | 2014 |
| Industry Online Limited | Information & communication | 2010 |
| Infinity Aesthetics Limited | Health & social care | 2020 |
| Infinity Management & Recruitment Services Ltd | Professional & scientific | 2025 |
| Infinity Occupational Health Limited | Health & social care | 2015 |
| Infinity Professional Services Ltd | Administrative & support | 2023 |
| Influenceeq Limited | Professional & scientific | 2021 |
| Influx Health & Performance Ltd | Health & social care | 2025 |
| Informed Productions Limited | Information & communication | 2019 |
| Inhouse Ents Ltd | Manufacturing | 2012 |
| Inicio Global Consulting Ltd | Professional & scientific | 2025 |