| Inside Voice (NE) Community Interest Company | Health & social care | 2025 |
| Insight Agile Ltd | Information & communication | 2018 |
| Insightcore Analytics Ltd | Information & communication | 2026 |
| Inspayer Limited | Manufacturing | 2024 |
| Inspearational Travels Limited | Professional & scientific | 2005 |
| Inspection & Quality Services Ltd | Professional & scientific | 2018 |
| Inspire Financial (North East) Limited | Professional & scientific | 2026 |
| Inspire Multi Academy Trust | Education | 2012 |
| Inspire Studios Sunderland Ltd | Arts & recreation | 2025 |
| Instaclad (NE) Ltd | Construction | 2024 |
| Instadec Ltd | Construction | 2022 |
| Instaflor Ltd | Construction | 2017 |
| Instaglam Prom Ltd | Wholesale & retail | 2019 |
| Instant Clearances Ltd | Administrative & support | 2025 |
| Instrument Access Ltd | Professional & scientific | 2022 |
| Integer Investments Europe Ltd | Real estate | 2023 |
| Integrated Ceiling Services Limited | | 1961 |
| Integrated Engineering Management Ltd | Construction | 2024 |
| Integrity Building Services Limited | Construction | 2024 |
| Intelex Developments Ltd | Real estate | 2020 |
| Intelex Ltd | Construction | 2012 |
| Intellicloud Solutions Ltd | Information & communication | 2018 |
| Intergas UK Ltd | Wholesale & retail | 2006 |
| Interior Designs (N.E) Ltd | Wholesale & retail | 2010 |
| International Niemann-Pick Disease Alliance | Information & communication | 2012 |
| International Niemann-Pick Disease Registry | Information & communication | 2017 |
| International Organization for Artificial Intelligence Ltd | Professional & scientific | 2025 |
| International Society for Rapid Response Systems | Professional & scientific | 2014 |
| Introco Ltd | Wholesale & retail | 2020 |
| INVIGOR8 North East Community Interest Company | Arts & recreation | 2023 |
| IP Consulting Management Ltd | Professional & scientific | 2020 |
| Ipca Laboratories UK Limited | Manufacturing | 2003 |
| IPE Assets Ltd | Wholesale & retail | 2024 |
| IPE Retail Ltd | Wholesale & retail | 2023 |
| Iqms Learning Ltd | Education | 2020 |
| Irecycle International Limited | Water & waste | 2024 |
| Irevolution Claims (Holdings) Limited | Professional & scientific | 2021 |
| Irevolution Claims Limited | Financial services | 2020 |
| Irevolution Extra (Holdings) Limited | Financial services | 2021 |
| Irevolution Group (Holdings) Limited | Financial services | 2023 |
| Irevolution Group Limited | Professional & scientific | 2015 |
| Irevolution Investments Limited | Administrative & support | 2023 |
| Irevolution Repair Network Limited | Wholesale & retail | 2026 |
| Iris Learning Trading Limited | Education | 2017 |
| Iris Learning Trust | Education | 2017 |
| IS This YOU Digital Ltd | Information & communication | 2026 |
| IS This YOU Ltd | Professional & scientific | 2024 |
| Islam Bros (NE) Ltd | Hospitality | 2026 |
| Ismatic Engineering Limited | Professional & scientific | 2020 |
| ISO Data Solutions Limited | Professional & scientific | 2018 |
| Isolutions Labs Limited | Information & communication | 2020 |
| ISP Holdings Ltd | Wholesale & retail | 2024 |
| IT UP Cuisines Ltd | Hospitality | 2024 |
| Itech Fire & Security Limited | Administrative & support | 2017 |
| Iter Solutions Ltd | Information & communication | 2013 |
| Itsconsult Ltd | Education | 2025 |
| ITY Digital Ltd | Information & communication | 2026 |
| Ivys Solutions Limited | Professional & scientific | 2026 |
| Ivyxclusive Rental Services Ltd | Wholesale & retail | 2026 |
| Izent Global Ltd | Information & communication | 2025 |
| J & C Graham Limited | Hospitality | 2015 |
| J & F Precision (Sunderland) Limited | Construction | 2011 |
| J & J Timber Limited | Construction | 2017 |
| J & K Cakes Limited | Wholesale & retail | 2020 |
| J & K Transport - Service Limited | Wholesale & retail | 2025 |
| J & N Lettings Limited | Real estate | 2021 |
| J & S Blyth Properties Limited | Real estate | 2025 |
| J + T Lettings Limited | Construction | 2008 |
| J and G Plumbing Heating Ltd | Construction | 2020 |
| J Brothers NE Ltd | Hospitality | 2020 |
| J Bulotiene Recycle Ltd | Water & waste | 2025 |
| J Carman Electrical Services Ltd | Construction | 2022 |
| J Farquhar Wind Ltd | Construction | 2026 |
| J G & G Ltd | Manufacturing | 2005 |
| J G H Project Limited | Health & social care | 2019 |
| J G P Investco Limited | Financial services | 2017 |
| J Gibson Services Ltd | Professional & scientific | 2023 |
| J Glass Trade Frames Ltd | Construction | 2023 |
| J Gosling Inspection Ltd | Professional & scientific | 2019 |
| J Hall Ultrasound Services Limited | Health & social care | 2015 |
| J Hilton Ltd | Transport & logistics | 2017 |
| J Jomson UK Ltd | Wholesale & retail | 2023 |
| J Lonsdale Limited | Construction | 2023 |
| J M C Fitness Limited | Arts & recreation | 2014 |
| J Murray Wall and Floor Ceramic Tiling Specialists Limited | Construction | 2008 |
| J Pearce Electrical Limited | Professional & scientific | 2013 |
| J S Locum Services Limited | Wholesale & retail | 2010 |
| J S Welch CD Ltd | Administrative & support | 2026 |
| J Slater Properties Ltd | Hospitality | 2025 |
| J T Taverns Limited | Real estate | 2011 |
| J Thompson Joinery Limited | Construction | 2022 |
| J&A Clothing Limited | Wholesale & retail | 2026 |
| J&B Enterprises Ltd | Wholesale & retail | 2021 |
| J&D Group Ltd | Administrative & support | 2025 |
| J&J PVT Ltd | Wholesale & retail | 2023 |
| J&M Medical NE Ltd | Wholesale & retail | 2020 |
| J&M Warehouse Retail Limited | Wholesale & retail | 2019 |
| J&S News Ltd | Wholesale & retail | 2024 |
| J&W Collective Limited | Professional & scientific | 2025 |
| J. & S. (Site Services) Limited | Water & waste | 1982 |