| Harrison Properties Limited | Real estate | 1980 |
| Harrop Leisure Ltd | Hospitality | 2024 |
| Harvey Capital Management Limited | Real estate | 2025 |
| Harvey Group (Northern) Limited | Financial services | 2024 |
| Harvey Properties (Northern) Limited | Real estate | 2018 |
| Harvey Property Group (Northern) Ltd | Real estate | 2025 |
| Hashtan Ltd | Other services | 2025 |
| Hauke Capital Limited | Administrative & support | 2022 |
| Haul Applications Ltd | Information & communication | 2026 |
| Haystacks Nursery Holdings Ltd | Financial services | 2025 |
| Haystacks Nursery Ltd | Health & social care | 2020 |
| Hayton & Lamb Limited | Construction | 1982 |
| HBX Holdings Limited | Financial services | 2020 |
| HC35 Engineering Limited | Professional & scientific | 2013 |
| Heating World of Spares Limited | Wholesale & retail | 2006 |
| Helix Innovations International Limited | Professional & scientific | 2016 |
| Heritage Timber Windows Ltd | Construction | 2025 |
| Heuvel Limited | Professional & scientific | 2023 |
| Hh&L Holdings (Teesside) Limited | Financial services | 2024 |
| High Times Consultancy Limited | Professional & scientific | 2015 |
| Hill PMG Ltd | Real estate | 2025 |
| Hillcrest Recruitment Solutions Ltd | Administrative & support | 2017 |
| Hillside Promotions and Events Limited | Administrative & support | 2023 |
| Hilo Airsports Ltd | Other services | 2025 |
| HJ Stead Limited | Professional & scientific | 2023 |
| Holdan & Jackson Associates Ltd | Professional & scientific | 2001 |
| Holdmethod Limited | Wholesale & retail | 1991 |
| Home Hardware Northeast Limited | Wholesale & retail | 2007 |
| Home Sweet Home Teesside Limited | Real estate | 2024 |
| Homeplan. DIY Limited | Wholesale & retail | 2013 |
| Homes by Carlton (Lanchester) Limited | Real estate | 2021 |
| Homes by Carlton (MSTG1) Limited | Construction | 2018 |
| Homes by Carlton (Redmarshall) Limited | Construction | 2018 |
| Homes by Carlton (Sadberge) Limited | Real estate | 2021 |
| Homes by Carlton (Snape) Limited | Construction | 2025 |
| Homes by Carlton (Staindrop) Limited | Construction | 2021 |
| Homes by Carlton (Thorpe Thewles) Limited | Construction | 2018 |
| Homes by Carlton (Whitton) Investment Company Limited | Real estate | 2021 |
| Homes by Carlton (Whitton) Limited | Construction | 2021 |
| Homes by Carlton Development Company (MSTG1) Limited | Construction | 2018 |
| Homes by Carlton Development Company (Redmarshall) Limited | Construction | 2018 |
| Homes by Carlton Development Company (Thorpe Thewles) Limited | Construction | 2018 |
| Homes by Carlton Ltd | Construction | 2017 |
| Horizon Aquatics Ltd | Wholesale & retail | 2019 |
| Horizons Durham Ltd | Real estate | 2023 |
| Horizons Global Ltd | Real estate | 2023 |
| Horizons Investment INT. Ltd | Real estate | 2017 |
| Horizons Partners Limited | Real estate | 2023 |
| Host & Clean Group Limited | Real estate | 2023 |
| House of Eden Limited | Education | 2001 |
| Houston Commercial Ltd | Real estate | 2003 |
| Howarth Limited | Manufacturing | 1997 |
| HTC Floor Systems Limited | Wholesale & retail | 2007 |
| HTM (NE) Limited | Professional & scientific | 2024 |
| Hudson and Sons Windows Limited | Construction | 2021 |
| Husqvarna Pension Scheme Trustee Limited | Financial services | 2005 |
| Husqvarna UK Limited | Manufacturing | 1970 |
| Hydraspecma Samwon Ltd | Manufacturing | 2003 |
| I L S Electrical Contractors Limited | Construction | 2010 |
| IAN Lamb Decorating Limited | Construction | 2012 |
| IDU Services Ltd | Transport & logistics | 2026 |
| IMA Europe Ltd | Administrative & support | 2017 |
| Improving Teaching Limited | Education | 2024 |
| IN the Pink Leisure Ltd | Wholesale & retail | 2020 |
| Incluscape Ltd | Professional & scientific | 2024 |
| Indulgence Hair Limited | Other services | 2015 |
| Industrial Heating Services Limited | Construction | 2000 |
| Inframe Space Ltd | Construction | 2020 |
| Innovate County Durham Limited | Hospitality | 2013 |
| Innovixx Digital Limited | Information & communication | 2023 |
| Intellifm Ltd | Information & communication | 2025 |
| Intelligence Software Group Limited | Information & communication | 2018 |
| Invest People Group Ltd | Professional & scientific | 2022 |
| Invest Training Limited | Education | 2023 |
| Investment Box Limited | Education | 2017 |
| ION Innovation Limited | Manufacturing | 2021 |
| ION Precision Limited | Manufacturing | 1998 |
| Iona MAE Aesthetics Ltd | Other services | 2023 |
| ISO Systems UK Limited | Professional & scientific | 2008 |
| ISP Holdings (U.K.) Ltd. | Manufacturing | 1999 |
| Iyah Properties Limited | Professional & scientific | 2024 |
| J & J Logistics (N/E) Limited | Transport & logistics | 2021 |
| J and J Logistics East Ltd | Transport & logistics | 2023 |
| J C Competency and Training Limited | Education | 2015 |
| J R a Software Limited | Information & communication | 2012 |
| J Robson Developments Limited | Construction | 2023 |
| J'S Healthcare Ltd | Wholesale & retail | 2017 |
| J.A.K.E. Logistics Ltd | Transport & logistics | 2012 |
| J59 Agricultural, Reclamation & Roofing Services Ltd | Construction | 2025 |
| Jack Angus Builders Ltd | Construction | 2024 |
| Jahanco Ltd | Administrative & support | 2025 |
| Jake Palliser Ltd | Transport & logistics | 2026 |
| JAM Compliance & Consultancy Ltd | Professional & scientific | 2022 |
| Jaxx Roofing Limited | Construction | 2022 |
| Jayt Properties Limited | Real estate | 2024 |
| JB Holdings (SE) Ltd | Financial services | 2024 |
| Jcfm Services Ltd | Mining & quarrying | 2016 |
| JG Financial Holdings Limited | Financial services | 2025 |
| JMG Consulting Services Ltd | Professional & scientific | 2018 |
| John Anderson Limited | Professional & scientific | 2022 |