| Injector Removal Service South West Ltd | Extraterritorial | 2024 |
| Inked Walls Ltd | Manufacturing | 2022 |
| Inkin & Deans Holdings Ltd | Financial services | 2024 |
| Inkspire Creative Studio Limited | Professional & scientific | 2025 |
| Inmeals Limited | Hospitality | 1986 |
| Innate Food Limited | Manufacturing | 2016 |
| Inngot Limited | Information & communication | 2007 |
| Innovaciones Barbara Alonzo Ltd | Financial services | 2025 |
| Innovative Care Limited | Health & social care | 2021 |
| Innovative Governance and Compliance Solutions Limited | Professional & scientific | 2024 |
| Innovative Qara Solutions Limited | Professional & scientific | 2015 |
| Innovative Railway Safety Ltd | Transport & logistics | 2011 |
| Innovura Marketing Limited | Wholesale & retail | 2019 |
| Inside OUT Renders Limited | Construction | 2025 |
| Inside the Vault Limited | Wholesale & retail | 2020 |
| Insighted Solutions Ltd | Professional & scientific | 2026 |
| Inspiration Limited | Manufacturing | 1994 |
| Inspirational Education Limited | Education | 2024 |
| Inspirational Packaging Limited | Wholesale & retail | 2012 |
| Inspirational Property Ltd | Real estate | 2017 |
| Inspire 2BU Ltd | Professional & scientific | 2019 |
| Inspire Training (GE) Limited | Education | 2016 |
| Inspirebuilding Limited | Construction | 2023 |
| Inspired Aroma Ltd | Manufacturing | 2020 |
| Inspired Property Factors Limited | Hospitality | 2010 |
| Inspired SA Limited | Real estate | 2019 |
| Inspired TEK Ltd | Wholesale & retail | 2020 |
| Inspo Life Limited | Education | 2024 |
| Instaspa Swansea Ltd | Health & social care | 2024 |
| Instinct Wear Limited | Wholesale & retail | 2025 |
| Institutional Consulting Limited | Professional & scientific | 2019 |
| Instrumentation and Process Systems (Southern) Limited | Wholesale & retail | 1988 |
| Insubloc Ltd | Wholesale & retail | 2025 |
| Insulation Installers South Wales Ltd | Other services | 2024 |
| Insurance Risk Consultancy Services Limited | Financial services | 1997 |
| Insure 4 YOU Ltd | Professional & scientific | 2019 |
| Insursystems Limited | Information & communication | 2026 |
| Integral Merchants Ltd | Wholesale & retail | 2020 |
| Integrated Health Consulting Ltd | Health & social care | 2026 |
| Integrative Therapy Wales Ltd | Health & social care | 2021 |
| Intelligent Business Tools Limited | Information & communication | 2000 |
| Intelligent Emotion Limited | Professional & scientific | 2015 |
| Intellisense Source Ltd | Information & communication | 2013 |
| Inter-Development Consulting Education Ltd | Professional & scientific | 2007 |
| Interexec Global Limited | Administrative & support | 2025 |
| Intergreen Construction Limited | Construction | 2008 |
| Interior Splash Studio Ltd | Arts & recreation | 2020 |
| Interlaid Limited | Wholesale & retail | 2013 |
| Interlaid Services Limited | Construction | 2017 |
| Internal Affairs Studio Limited | Information & communication | 2025 |
| International Centre for Manufacture by Printing Limited | Professional & scientific | 2009 |
| International Food Swansea Limited | Wholesale & retail | 2022 |
| International Land Registration Consultancy Services Limited | Professional & scientific | 2011 |
| International Society of Performance Analysis of Sport Ltd | Information & communication | 2020 |
| International Swansea Food Centre Ltd | Wholesale & retail | 2026 |
| International Workplace Solutions Ltd | Construction | 2019 |
| Interplay (Integrated Play and Leisure) | Health & social care | 1996 |
| Intrinsic Aura Limited | Construction | 2018 |
| Intstrength Ltd | Education | 2023 |
| Investb Limited | Professional & scientific | 2025 |
| Investicat Limited | Information & communication | 2024 |
| Investment Representation Services Limited | Financial services | 2017 |
| Invicta PM & D Limited | Professional & scientific | 2014 |
| Involved Property Investments Ltd | Real estate | 2021 |
| INX Direct Limited | Wholesale & retail | 2003 |
| INYATS76501 PLC | Financial services | 2025 |
| Ionita Expres Limited | Other services | 2019 |
| Iorio Group Limited | Construction | 2021 |
| Iplan Architecture Ltd | Professional & scientific | 2013 |
| Ipog Estates Ltd | Real estate | 2024 |
| Ipoh Ltd | Construction | 2024 |
| Ipulse Direct Limited | Administrative & support | 2014 |
| Ipulse Limited | Manufacturing | 2012 |
| Iris International Infrastructures Limited | Construction | 2013 |
| Iris Logistics Services Ltd | Wholesale & retail | 2026 |
| Ironcave Ltd | Manufacturing | 2025 |
| Irongate Fabrications Limited | Professional & scientific | 2022 |
| Irontriswim Limited | Arts & recreation | 2012 |
| Irosilda Properties Ltd | Financial services | 2025 |
| Irresistible Materials Ltd | Professional & scientific | 2009 |
| Irvine Court Management Limited | Households | 2007 |
| Irwin Capital Management Limited | Professional & scientific | 2016 |
| IS3 Teamwear Limited | Wholesale & retail | 2025 |
| Isaac Motors Limited | Wholesale & retail | 2022 |
| Ischooldigital Limited | Education | 2015 |
| ISG Events Ltd | Administrative & support | 2018 |
| ISG Properties Ltd | Administrative & support | 2016 |
| ISG Sports Events Ltd | Administrative & support | 2018 |
| Ishtikutum Ltd | Hospitality | 2017 |
| Islim Ltd | Health & social care | 2020 |
| Islwyn Gymnastics Club Limited | Education | 2018 |
| ISO and Pharma Consultancy Services Limited | Professional & scientific | 2026 |
| ISO Business Certification Corp Limited | Information & communication | 2020 |
| Isports Tours Ltd | Administrative & support | 2019 |
| Isrecalled Ltd | Information & communication | 2025 |
| ISS Distribution Services Limited | Transport & logistics | 2007 |
| Istanbul Restaurant (Swansea) Ltd | Hospitality | 2017 |
| Istg Limited | Health & social care | 2013 |
| Isufi Transport UK Ltd | Transport & logistics | 2026 |
| IT Migration Services Limited | Information & communication | 2014 |