| Hutton Fire Protection Limited | Other services | 2016 |
| Hwajiting Ltd | Other services | 2010 |
| Hydrastone Ltd | Mining & quarrying | 2026 |
| Hydrochem (U.K.) Limited | Manufacturing | 1990 |
| Hydrochem Associates Ltd | Financial services | 2020 |
| Hypehaven Limited | Wholesale & retail | 2025 |
| I C Plumbing Services Ltd | Construction | 2010 |
| I Danby Properties Ltd | Real estate | 2026 |
| I Love Wallpaper Ltd | Extraterritorial | 2021 |
| I O Gavrila Limited | Construction | 2021 |
| I&J PFP Consultants Limited | Administrative & support | 2024 |
| I.C.E Properties Ltd | Real estate | 2019 |
| IAN Bond Brickwork Limited | Construction | 2015 |
| IAN Elliott Consultants Limited | Professional & scientific | 2017 |
| Ibbotson Comms Ltd | Construction | 2026 |
| Iboski African Shop Limited | Wholesale & retail | 2023 |
| Icarus Futures Ltd | Health & social care | 2025 |
| Ice (Onshore/Offshore) Limited | Construction | 2012 |
| IDL Design Limited | Professional & scientific | 2006 |
| IFM Investments Limited | Financial services | 2026 |
| IG Fitness Ltd | Health & social care | 2025 |
| IG Medical & Occupational Health Limited | Health & social care | 2026 |
| Ignite Candles Ltd | Wholesale & retail | 2025 |
| Igomove County Durham Limited | Real estate | 2019 |
| Igomove Darlington Limited | Real estate | 2023 |
| Igomove Durham North West Limited | Real estate | 2022 |
| Igomove Limited | Real estate | 2018 |
| Igomove Teesside Limited | Real estate | 2020 |
| IHK Electrical Limited | Manufacturing | 2016 |
| Ihtec Ltd | Construction | 2021 |
| Ijjsp Ltd | Construction | 2014 |
| IJT Holdings Limited | Financial services | 2026 |
| IK Group Holdings Limited | Financial services | 2026 |
| Iles Forestry Limited | Agriculture & fishing | 2018 |
| ILP Properties Limited | Real estate | 2004 |
| Imagination Village Ltd | Arts & recreation | 2019 |
| Imaginative Living Limited | Construction | 2006 |
| Imaginatively Superior Art Work Company Ltd | Arts & recreation | 2022 |
| IMC Windows Limited | Construction | 2016 |
| Impact Dents Limited | Wholesale & retail | 2004 |
| Imray Digital Ltd | Information & communication | 2022 |
| IN the Frame Collective Ltd | Information & communication | 2025 |
| In-Between Worlds Ltd | Health & social care | 2025 |
| Inayah Tandoori Ltd | Hospitality | 2023 |
| Incontrol-Able Community Interest Company | Health & social care | 2008 |
| Indaba Holdings Ltd | Construction | 2018 |
| Industrial Asset Management Technology Limited | Professional & scientific | 2014 |
| Ingleby Consulting Limited | Professional & scientific | 2019 |
| Ingrain-Spe Limited | Professional & scientific | 2018 |
| Inkkpit Ltd | Real estate | 2023 |
| Innovagent AI Ltd | Information & communication | 2025 |
| Innovation and Project Management Engineering Ltd | Professional & scientific | 2023 |
| Innovative Advancements Ltd | Information & communication | 2024 |
| Innovative Electrical & Solar Solutions Ltd | Energy | 2025 |
| Innovative Roofing & Solar Ltd | Energy | 2025 |
| Insane Dancewear by Nadine Limited | Administrative & support | 2016 |
| Inspiration by Tori Limited | Other services | 2007 |
| Instaheat North Limited | Construction | 2022 |
| Instrument Automation Solutions Ltd | Professional & scientific | 2022 |
| Integrale Project Services Limited | Professional & scientific | 2018 |
| Integrated and Automated Solutions Limited | Manufacturing | 2021 |
| Integrated Modular Partitions Limited | Manufacturing | 1996 |
| Intellivate Limited | Information & communication | 2022 |
| INTERNET2YOU.CO.UK Ltd | Wholesale & retail | 2010 |
| IP Techni Limited | Professional & scientific | 2013 |
| IP3 Web Solutions Ltd | Information & communication | 2016 |
| IPM Consultancy Ltd | Professional & scientific | 2026 |
| Ipro Technology Ltd | Other services | 2023 |
| IR Taylor Renewables Limited | Construction | 2016 |
| Irinel Dragan Logistics Limited | Transport & logistics | 2025 |
| Isla Britannica Books Ltd | Information & communication | 2018 |
| Isocom Components 2004 Limited | Manufacturing | 2003 |
| IT Infrastucture UK Limited | Administrative & support | 2008 |
| ITC First AID Limited | Education | 2006 |
| ITS ALL About the Cake Limited | Hospitality | 2014 |
| IVF North East Limited | Health & social care | 2016 |
| IWS Building Solutions Limited | Construction | 2005 |
| Iykyk Business Solutions Limited | Professional & scientific | 2022 |
| Izzouse Ltd | Information & communication | 2020 |
| J & M Lowther Properties Limited | Real estate | 2022 |
| J & M Storage Ltd | Other services | 2025 |
| J & O Properties Limited | Real estate | 2015 |
| J & S UK Holdings Limited | Wholesale & retail | 2024 |
| J Barron Ltd | Extraterritorial | 2025 |
| J Clarke Inspection Ltd | Professional & scientific | 2024 |
| J Davison Financial Limited | Financial services | 2020 |
| J Denham Metals (Gateshead) Limited | Construction | 2026 |
| J Hardy Labour Ltd | Administrative & support | 2019 |
| J J a Renewables Ltd | Administrative & support | 2026 |
| J J Tones Safety Services Ltd | Other services | 2018 |
| J K Malcolm Limited | Agriculture & fishing | 2023 |
| J L R Plant & Machinery Limited | Construction | 2015 |
| J Mitchell Property Ltd | Real estate | 2020 |
| J T Dawson Plastering & Rendering Ltd | Construction | 2023 |
| J T Hodgman Ltd | Manufacturing | 2024 |
| J W Cockburn Ltd | Construction | 2016 |
| J Wallis Investments Ltd | Real estate | 2020 |
| J Wallis Leisure Ltd | Hospitality | 2013 |
| J&S Mayfield Holdings Ltd | Construction | 2022 |
| J&Sd Services Limited | Construction | 2025 |