| Inclusive Movement CIC | Arts & recreation | 2025 |
| Inclusive Tutoring Network Limited | Education | 2024 |
| Incut Hairdressing Ltd | Other services | 2009 |
| Independent Fire Consultants Ltd | Public administration | 2021 |
| Independent Fire Engineering Ltd | Public administration | 2020 |
| Independent Fire Inspection Body Ltd | Public administration | 2022 |
| Independent Fire Inspections Ltd | Public administration | 2015 |
| Independent Fire Training Ltd | Education | 2020 |
| Indigo 42 Ltd | Information & communication | 2022 |
| Industrial Diesel Power Ltd | Manufacturing | 2012 |
| Industrial Field Services Ltd | Manufacturing | 2023 |
| Industrial Turbine Services Ltd | Professional & scientific | 2008 |
| Indylby Investments Limited | Real estate | 2013 |
| Ineo Wealth Management Ltd | Financial services | 2019 |
| Infinity Barber Salon Ltd | Other services | 2026 |
| Infinity EC Ltd | Manufacturing | 2025 |
| Infinity Engineering Services Ltd | Manufacturing | 2016 |
| Infobalt Ltd | Professional & scientific | 2015 |
| Inforia Limited | Information & communication | 2016 |
| Infosec Compliance Consultants Limited | Information & communication | 2024 |
| Ingamells (UK) Limited | Wholesale & retail | 1983 |
| Ingamells Developments Limited | Construction | 1978 |
| Ingleby Hall Livery Ltd | Arts & recreation | 2015 |
| Ingriid Ltd | Transport & logistics | 2023 |
| Inhome Limited | Construction | 2014 |
| INK Cartridges Ltd | Wholesale & retail | 2002 |
| Inn on the Green (FLY Girl) Ltd | Hospitality | 2019 |
| Inner Current Ltd | Other services | 2025 |
| Inner Force Martial Arts Limited | Arts & recreation | 2024 |
| Inner Lifetime Ltd | Health & social care | 2026 |
| INNOV8 Coatings Ltd | Wholesale & retail | 2020 |
| Innovative Technologies & Tribology Ltd | Professional & scientific | 2009 |
| Inol Ltd | Construction | 2018 |
| Insight for Impact CIC | Education | 2019 |
| Insightful Training Limited | Extraterritorial | 2018 |
| Insignia Bathroom Solutions Ltd | Construction | 2011 |
| Insignia Interiors (Group) Ltd | Wholesale & retail | 2016 |
| Insignia Interiors Group (UK) Ltd | Wholesale & retail | 2020 |
| Insignia Interiors Ltd | Wholesale & retail | 2016 |
| Inspire Learning Solutions Ltd | Professional & scientific | 2021 |
| Inspire Pharma Ltd | Wholesale & retail | 2025 |
| Inspire Textiles Ltd | Professional & scientific | 2014 |
| Inspired Designer Kitchens Ltd | Manufacturing | 2019 |
| Inspired Life Group Ltd | Health & social care | 2025 |
| INSPIRED2BE Ltd | Education | 2008 |
| Instagas Ltd | Wholesale & retail | 2011 |
| Installation Maintenance Services Electrical Limited | Construction | 2010 |
| Integrated Medical Consulting Ltd | Professional & scientific | 2026 |
| Integrity Energy Services Ltd | Professional & scientific | 2012 |
| Intelligence Innovation Solutions Limited | Professional & scientific | 2019 |
| Inter Haul Ltd | Transport & logistics | 2021 |
| Intergold Ltd | Wholesale & retail | 2021 |
| Interlinkin Ltd | Wholesale & retail | 2014 |
| Intermedcom Limited | Health & social care | 2011 |
| International Auto OEM Supplier Ukco Ltd. | Manufacturing | 2017 |
| International Bomber Command Centre Limited | Hospitality | 2017 |
| International Bowel Experts LLP | | 2018 |
| International Classics Ltd. | Professional & scientific | 2013 |
| International Coalition of Respiratory Nurses Limited | Other services | 2023 |
| International Management Services (Attleborough) Limited | Professional & scientific | 2019 |
| International Trade Masters (ITM) Ltd | Wholesale & retail | 2025 |
| Interpredata Limited | Information & communication | 2020 |
| Interwaste Limited | Water & waste | 2001 |
| Intotale Ltd | Information & communication | 2025 |
| Intrepid Blue Limited | Real estate | 2016 |
| Intrinsic Properties Ltd | Real estate | 2026 |
| Intuidat Ltd | Wholesale & retail | 2013 |
| Invest in Habitats Ltd | Real estate | 2019 |
| Investment Brics Ltd | Real estate | 2019 |
| Investors Campus Limited | Administrative & support | 2024 |
| Investors in Lincoln Limited | Real estate | 1991 |
| Investors Platform Ltd | Real estate | 2024 |
| Invicta Consultants Limited | Professional & scientific | 2016 |
| Invictus Trading Solutions Limited | Administrative & support | 2018 |
| Invp Ltd | Real estate | 2025 |
| Inxtattoo Ltd | Other services | 2025 |
| Inxterior Limited | Construction | 2015 |
| Inzpire Limited | Public administration | 2005 |
| Iocea.Com Limited | Information & communication | 2000 |
| Ionzie Ltd | Manufacturing | 2022 |
| IPC Transporter Limited | Transport & logistics | 2025 |
| Iperion Consultancy Limited | Professional & scientific | 2015 |
| Iprint Textile Designs Limited | Manufacturing | 2010 |
| IQ Financial Advice Limited | Financial services | 2012 |
| Irimias Medical Consulting Ltd | Health & social care | 2026 |
| Iris Analytics Consultancy Ltd | Information & communication | 2025 |
| Irisinframe Ltd | Professional & scientific | 2025 |
| Iron Horse Industries Limited | Manufacturing | 2010 |
| Ironway Logistics Ltd | Transport & logistics | 2026 |
| Irvine Enterprises Ltd | Health & social care | 2010 |
| Isabela E-Commerce Ltd | Wholesale & retail | 2025 |
| Ishu Physio Centre Ltd | Health & social care | 2016 |
| Isikhova Ltd | Health & social care | 2021 |
| Isis Commodities Ltd | Administrative & support | 2005 |
| Isla Safety Solutions (ISS) Limited | Information & communication | 2022 |
| Island GAS (Singleton) Limited | Mining & quarrying | 1971 |
| Island GAS Limited | Mining & quarrying | 2003 |
| Island GAS Operations Limited | Energy | 2000 |
| Islay Properties Ltd | Real estate | 2021 |
| Ispec Spaces Limited | Real estate | 2022 |