| Intellisims Limited | Information & communication | 2015 |
| Inter Global Forwarding Limited | Transport & logistics | 1997 |
| Intera Data Systems Ltd | Information & communication | 2025 |
| Interact UK Holdings Limited | Professional & scientific | 2001 |
| Interactive Development Support Limited | Health & social care | 2002 |
| Interactive Referral Network Limited | Administrative & support | 2019 |
| Interdigitate Support Services Limited | Professional & scientific | 2019 |
| Interglobe Trade Limited | Wholesale & retail | 2020 |
| Interiora Ltd | Construction | 2024 |
| Internal Audit Connections Ltd | Administrative & support | 2011 |
| International Advisory Experts Limited | Information & communication | 2016 |
| International B2G Consortium Ltd | Mining & quarrying | 2010 |
| International Centre for Life (Property) Limited | Hospitality | 1996 |
| International Centre for Life (Trading) Limited | Extraterritorial | 1996 |
| International Centre for Life Trust | Professional & scientific | 1996 |
| International China Concern (Child Care) Ltd | Administrative & support | 2002 |
| International Combustion Riley Limited | | 1924 |
| International Education Service Arab World Ltd | Education | 2004 |
| International Fitness Alliance Limited | Education | 2015 |
| International Food Newcastle Ltd | Wholesale & retail | 2022 |
| International House Newcastle Teacher Training Limited | Education | 1997 |
| International Jurists Limited | Professional & scientific | 2006 |
| International Language College Ltd | Education | 2022 |
| International Newcastle C.I.C. | Administrative & support | 2012 |
| International Pipeline Consultants Limited | Professional & scientific | 2025 |
| International Space Station (ISS) Airlines Limited | Transport & logistics | 2025 |
| International Space Station (ISS) Freeports Limited | Real estate | 2025 |
| International Space Station (ISS) Tees Valley Limited | Construction | 2025 |
| International Space Station (ISS) Top Co Limited | Real estate | 2026 |
| International Timber Merchants Ltd | Construction | 2025 |
| International Training and Work Recruitment Limited | Administrative & support | 2016 |
| Interplay Design Ltd | Professional & scientific | 2021 |
| Intersoil Limited | Professional & scientific | 2004 |
| Interval Records Limited | Information & communication | 2023 |
| Intimo Ltd | Hospitality | 2026 |
| Into Technology Limited | Wholesale & retail | 2013 |
| Intobeige Limited | Health & social care | 1983 |
| Intouch Advance Limited | Information & communication | 2001 |
| Intouch Physiotherapy Services Ltd | Health & social care | 2019 |
| Intrain Solutions Limited | Professional & scientific | 2011 |
| Intriga Ltd | Information & communication | 2020 |
| Introspection Holdings Ltd | Real estate | 2024 |
| Intuition Learning Ltd | Education | 2020 |
| Intune Clinic Limited | Health & social care | 2014 |
| Invenirex Ltd | Professional & scientific | 2021 |
| Inver River Projects Limited | Professional & scientific | 2018 |
| Inversion Investments Limited | Financial services | 2023 |
| Invest One (MS) Ltd | Real estate | 2021 |
| Invest One Developments Ltd | Real estate | 2008 |
| Investabrick Ltd | Information & communication | 2022 |
| Investco Group Unlimited | Financial services | 2016 |
| Investment Investments Limited | Real estate | 2022 |
| Investment Properties Private Ltd | Real estate | 2025 |
| Invicta Public Affairs (England) Limited | Professional & scientific | 2015 |
| Invicta Public Affairs (Group) Limited | Professional & scientific | 2015 |
| Invicta Public Affairs (Manchester) Limited | Extraterritorial | 2025 |
| Invicta Public Affairs (Scot) Limited | Professional & scientific | 2016 |
| Invicta Public Affairs (Wales) Limited | Professional & scientific | 2015 |
| Invictus Business Consultants Ltd | Professional & scientific | 2013 |
| Inville Management Limited | Hospitality | 2016 |
| Invincible Brands Ltd | Administrative & support | 2021 |
| Invisible Rules Community Interest Company | Arts & recreation | 2024 |
| Invoke Heating Ltd | Construction | 2024 |
| Involve North East | Health & social care | 2006 |
| IO Design Solutions Ltd | Professional & scientific | 2024 |
| Io&Oa Limited | Transport & logistics | 2025 |
| ION Energies Limited | Manufacturing | 2018 |
| ION Industries Ltd | Information & communication | 2016 |
| ION Limited | Information & communication | 1996 |
| Iona HR Consulting Ltd | Professional & scientific | 2024 |
| Ionex Ltd | Real estate | 2024 |
| Ionic Upgrades Ltd | Information & communication | 2025 |
| Ionist Ltd | Professional & scientific | 2025 |
| IOP Health Limited | Information & communication | 2015 |
| Iotnikuk Ltd | Health & social care | 2018 |
| Ip-Soft Limited | Information & communication | 1997 |
| IP2IMPACT Ltd | Professional & scientific | 2022 |
| IPD Health & Safety Services Limited | Professional & scientific | 2015 |
| Ipdistribution SRL Limited | Construction | 2025 |
| IPG Estates Ltd | Real estate | 2024 |
| Iprt Group Ltd | Other services | 2017 |
| IPS Newcastle Ltd | Manufacturing | 1984 |
| IQ Automotive Ltd | Wholesale & retail | 2024 |
| IQ Collection Ltd | Wholesale & retail | 2022 |
| Iqbal Pharma Ltd | Health & social care | 2014 |
| Irdalex Tidying UP Ltd | Administrative & support | 2021 |
| IRENOV8 & Refurbish Ltd | Construction | 2024 |
| Iriana Convenience Store Ltd | Wholesale & retail | 2022 |
| Iribel Limited | Hospitality | 2022 |
| Irim ALI Solicitors Ltd | Professional & scientific | 2024 |
| Irish Lokhi Ltd | Health & social care | 2026 |
| Irons Technical Limited | Professional & scientific | 2007 |
| Ironwill Fitness Ltd | Wholesale & retail | 2024 |
| Irukpizza Ltd | Hospitality | 2021 |
| Irving Advisory Limited | Administrative & support | 2021 |
| IS Promotions and Consultants to the Lesuire Industry Ltd | Manufacturing | 2026 |
| ISA (T/A Property Management) Limited | Hospitality | 2012 |
| Isaa Holdings Limited | Financial services | 2010 |
| Isaac Walton Tailoring Ltd | Wholesale & retail | 2014 |
| Isabsuk Ltd | Professional & scientific | 2026 |