| HV Testing and Design Ltd | Construction | 2020 |
| Hydepark Malton Ltd | Hospitality | 2026 |
| Hygia Professional Training & Assessment Ltd | Education | 2006 |
| Hyve Property Limited | Construction | 2018 |
| I & J Property Investments Limited | Real estate | 2017 |
| I BE Properties Limited | Construction | 2015 |
| I T Training Solutions Limited | Information & communication | 1999 |
| I&H Limited | Hospitality | 2023 |
| I&J Wilson Group Limited | Financial services | 2025 |
| I&J Wilson Properties Limited | Real estate | 2025 |
| I.Morrow Ltd | Construction | 2026 |
| IA Commercials Limited | Real estate | 2022 |
| IAN Carswell Associates Limited | Construction | 2000 |
| IAN Dixon Ltd | Information & communication | 2012 |
| Ibam Group Ltd | Financial services | 2022 |
| Iberico Star Limited | Hospitality | 2023 |
| Iccf Limited | Professional & scientific | 2010 |
| Ice MAN Restoration Limited | Administrative & support | 2025 |
| Ideal Caravan Sales Limited | Wholesale & retail | 1972 |
| Identify International Ltd | Administrative & support | 2017 |
| IF YOU ARE Safe I AM Safe | Public administration | 2015 |
| Ifix U.K Limited | Manufacturing | 2019 |
| Iglobe Platinum FD III Limited | Energy | 2025 |
| IHM Consulting Limited | Professional & scientific | 2021 |
| Iiwii Ltd | Transport & logistics | 2026 |
| IJF Heating Ltd | Construction | 2026 |
| Ilgen Limited | Wholesale & retail | 2025 |
| Imad-Muminah Properties Ltd | Real estate | 2010 |
| Imagejoinery NE Ltd | Construction | 2026 |
| Imladris Ltd | Real estate | 2023 |
| Immobi Ltd | Real estate | 2012 |
| Impact DSA Ltd | Professional & scientific | 2023 |
| Impact Paving NE Ltd | Construction | 2021 |
| Impactus Media Limited | Education | 2021 |
| Impeccable Bathroom Designs Ltd | Wholesale & retail | 2024 |
| Impetus One Limited | Real estate | 2026 |
| Implant Pro Limited | Health & social care | 2024 |
| IN Pera Ltd | Wholesale & retail | 2025 |
| Inclusive Development Resilience International Ltd | Professional & scientific | 2024 |
| Indigo Properties (NE) Ltd | Real estate | 2018 |
| Indigo Works Ltd | Construction | 2019 |
| Industrial & Commercial Clean Ltd | Administrative & support | 2025 |
| Industry (South Shields) Ltd | Hospitality | 2022 |
| Inej Wigs Limited | Wholesale & retail | 2025 |
| Infinite Ascent Limited | Professional & scientific | 2023 |
| Infinite Durham (Property) Limited | Financial services | 2025 |
| Infinite Durham (Trading) Limited | Arts & recreation | 2025 |
| Infinite Logistics 22 Ltd | Transport & logistics | 2022 |
| Infinite Pet Care Ltd | Other services | 2021 |
| Infinite Ventures Global Limited | Information & communication | 2025 |
| Infiniter Ltd | Manufacturing | 2024 |
| Infinity Dental Services (IDS) Ltd | Health & social care | 2011 |
| Infinity Photographic Studios Limited | Professional & scientific | 2013 |
| Infinity Properties North East Ltd | Real estate | 2024 |
| Infoceram Limited | Professional & scientific | 2003 |
| Infosec Data Systems Limited | Professional & scientific | 2010 |
| Infrasafe Rail and Safety Training Limited | Public administration | 2024 |
| Ingrey Ltd | Wholesale & retail | 2024 |
| Injoy Home Decoration Ltd | Wholesale & retail | 2021 |
| Inky Durham Limited | Wholesale & retail | 2026 |
| Inman's Transport Ltd | Transport & logistics | 2018 |
| Inn Brandon Limited | Hospitality | 2019 |
| Innerscape Limited | Professional & scientific | 2024 |
| Innovate NE Limited | Administrative & support | 2015 |
| Innovo Developments Durham Ltd | Construction | 2026 |
| Inovatrendy Ltd | Wholesale & retail | 2025 |
| Inside OUT Communications Consulting Ltd | Professional & scientific | 2019 |
| Insidez Ltd | Extraterritorial | 2017 |
| Insightful Psychology Ltd | Health & social care | 2022 |
| Inspire Fitness Solutions Limited | Wholesale & retail | 2003 |
| Inspire Solutions Services Ltd | Health & social care | 2025 |
| Inspired Lifestyles Ltd | Real estate | 2019 |
| Inspirovations Ltd | Information & communication | 2023 |
| Instant Surface Recovery Ltd | Administrative & support | 2022 |
| Insync Labs Limited | Professional & scientific | 2025 |
| Intec Electrical Engineering Ltd | Construction | 2023 |
| Integrative Health and Wellness CIC | Health & social care | 2026 |
| Intellecta Ltd | Information & communication | 2023 |
| Intellidental Ltd | Education | 2023 |
| Intelligent Networks Solutions Limited | Information & communication | 2015 |
| Interior Educators | Other services | 2008 |
| International Spill Accreditation Scheme Ltd | Professional & scientific | 2004 |
| Intrepid Tribe Limited | Administrative & support | 2023 |
| Intricate Ltd | Extraterritorial | 2025 |
| Intupay Group Ltd. | Other services | 2021 |
| Invent Group Limited | Information & communication | 2025 |
| INVERSIONES2025 Ltd | Wholesale & retail | 2025 |
| Invert Your World Limited | Agriculture & fishing | 2026 |
| Investor Management Services Ltd | Professional & scientific | 2018 |
| Invicta ENV Holdings Ltd | Financial services | 2026 |
| Invicta Environmental Ltd | Administrative & support | 2022 |
| Invicta Property Group Ltd | Real estate | 2025 |
| Ioscm International Ltd | Education | 2019 |
| Ipek LLC Ltd | Wholesale & retail | 2025 |
| Irecommended Ltd | Information & communication | 2020 |
| Iridium Technology Solutions Limited | Information & communication | 2004 |
| Ironworks Martial Arts C.I.C. | Arts & recreation | 2020 |
| Irts Property Maintenance Ltd | Construction | 2019 |
| Isecure Group Ltd | Administrative & support | 2018 |
| Islandshire Limited | Construction | 2017 |