| Independent School Travel Ltd | Administrative & support | 2014 |
| Indigi Origi Ltd | Manufacturing | 2015 |
| Indigo Graphics Ltd | Arts & recreation | 2016 |
| Indigo Platform Limited | Information & communication | 2020 |
| Indigo Service Solutions Limited | Construction | 2007 |
| Indomitable Technical Solutions Ltd. | Information & communication | 2013 |
| Industrial Automation and Control Holdings Limited | Professional & scientific | 2009 |
| Industrial Automation and Control Limited | Manufacturing | 1982 |
| Industrial Climbers Limited | Construction | 2005 |
| Industrial Door Holdings Ltd | Financial services | 2016 |
| Industrial Door Services Limited | Manufacturing | 1995 |
| Industrial Ductwork Limited | Construction | 1997 |
| Industrial Maintenance Consultants Limited | Professional & scientific | 2022 |
| Industrial Welfare Cleaning Services Ltd | Administrative & support | 2024 |
| Inexclusion CIC | Health & social care | 2025 |
| Inexclusion Group Ltd | Professional & scientific | 2026 |
| INF Solutions Ltd | Professional & scientific | 2013 |
| Inferno Catering (Wales) Ltd | Hospitality | 2022 |
| Infinite Auto Spraying Limited | Manufacturing | 2022 |
| Infiniti Care Services Ltd | Health & social care | 2020 |
| INFINITI2 Ltd | Construction | 2019 |
| Infinity Global Investments Ltd | Construction | 2026 |
| Inflight Peripherals Limited | Manufacturing | 1996 |
| Influzio Limited | Professional & scientific | 2025 |
| Infomap Surveys and Mapping Limited | Professional & scientific | 1986 |
| Informative Company Statistics Limited | Administrative & support | 1976 |
| Informed Training Limited | Information & communication | 2010 |
| Infraterra Property Europe Limited | Real estate | 2019 |
| Infraterra Property Italy LLP | | 2018 |
| Infraterra Property Poland LLP | | 2017 |
| Infrawork Capital Limited | Manufacturing | 2017 |
| Ingenstat Renewables Limited | Construction | 2024 |
| Ingley Apse Limited | Real estate | 2021 |
| Ingram Farriers Ltd | Other services | 2018 |
| Ingram Networks Ltd | Information & communication | 2016 |
| Initia Solutions Ltd | Information & communication | 2022 |
| Inmation UK Ltd | Information & communication | 2021 |
| Inner Beauty (Blackwood) Limited | Other services | 2013 |
| Inner Margins Ltd | Wholesale & retail | 2025 |
| Innovate Local Ltd | Professional & scientific | 2024 |
| Innovation Drive Newport Limited | Real estate | 2019 |
| Innovation Financial Consultancy LLP | | 2012 |
| Innovation Human Capital Limited | Professional & scientific | 2014 |
| Innovation Professional Services Limited | Information & communication | 2012 |
| Innovation Tax and Mileage Consulting Group Ltd | Financial services | 2018 |
| Innovative Risk Solutions Ltd | Information & communication | 2025 |
| Innovise Ltd | Professional & scientific | 2025 |
| Innozee Ltd | Wholesale & retail | 2024 |
| Inolux Ltd | Wholesale & retail | 2018 |
| Inqbate.Business Limited | Financial services | 2017 |
| Inside OUT Building and Landscaping Limited | Construction | 2016 |
| Inside REG Ltd | Administrative & support | 2019 |
| Insight HRC Ltd | Professional & scientific | 2021 |
| Insight International Group Limited | Construction | 2026 |
| Insight Workplace Safety Ltd | Public administration | 2018 |
| Insignia Crew Limited | Administrative & support | 2016 |
| Inspire Air Conditioning Ltd | Construction | 2023 |
| Inspired Bespoke Limited | Administrative & support | 2025 |
| Inspired Business Media Ltd | Administrative & support | 2013 |
| Inspired Purpose Ltd | Professional & scientific | 2015 |
| Instant Investments Limited | Real estate | 1998 |
| Instinct AI Systems Ltd | Information & communication | 2016 |
| INSURE24 Limited | Information & communication | 2011 |
| Insx UK Limited | Administrative & support | 2012 |
| Intalman Ltd | Arts & recreation | 2019 |
| Integrated Resilience Group Ltd | Hospitality | 2026 |
| Integratis Business Consulting Limited | Professional & scientific | 2014 |
| Integrevise Ltd | Information & communication | 2025 |
| Integrum Group Limited | Financial services | 2021 |
| Intellectual Language and Editing Services Ltd | Professional & scientific | 2018 |
| Intelligent Automotive Group Ltd | Wholesale & retail | 2019 |
| Intemporel Grocery CYF | Wholesale & retail | 2020 |
| Intensichem Group Limited | Extraterritorial | 2011 |
| Intensichem Solutions Limited | Professional & scientific | 2011 |
| Intercare Support Services Limited | Health & social care | 2023 |
| Interceptor Solutions Limited | Information & communication | 2011 |
| Interclad Property Services Limited | Construction | 2013 |
| Interclad Services Ltd | Construction | 2001 |
| Interface Developments Ltd | Professional & scientific | 2022 |
| Interim Accountancy Solutions Limited | Professional & scientific | 2008 |
| Interlec Systems (Newport) Limited | Construction | 2017 |
| Intermobilsrlservices Ltd | Construction | 2018 |
| International Convention Centre Wales Limited | Real estate | 2014 |
| International Quality Ltd | Information & communication | 2011 |
| Internet Radio Promotions Ltd | Information & communication | 2016 |
| Internet Video Solutions Ltd | Information & communication | 2016 |
| Interoncology Education & Prevention Limited | Administrative & support | 2018 |
| Intuitive Learning Solutions Ltd | Professional & scientific | 2025 |
| Intyme Limited | Professional & scientific | 2014 |
| Invaluable Group Limited | Information & communication | 1989 |
| Invenode Ltd | Information & communication | 2024 |
| Inventory Smart Limited | Administrative & support | 2022 |
| Invest to Grow Ltd | Real estate | 2021 |
| Invoke Evoke Limited | Hospitality | 2022 |
| IO Biotech Limited | Professional & scientific | 2021 |
| Iona Windows Cleaning Ltd | Administrative & support | 2024 |
| Iota Byteworks Limited | Information & communication | 2023 |
| IOW Consulting Limited | Professional & scientific | 2026 |
| IOW Developments Limited | Real estate | 2015 |
| IOW Espresso LLP | | 2008 |