| H2OFFSHORE Ltd | Construction | 2024 |
| HA Healthcare Ltd | Wholesale & retail | 2022 |
| HAB Entertainment Limited | Information & communication | 2021 |
| Haines Chemicals Limited | Wholesale & retail | 2013 |
| Haines Maintenance Limited | Administrative & support | 2012 |
| Haines Recruitment Limited | Administrative & support | 2012 |
| Haines Recycling Limited | Water & waste | 2013 |
| Haines Retail Limited | Wholesale & retail | 2012 |
| Haines Spa Limited | Manufacturing | 2012 |
| Hairhaus Hair & Beauty Limited | Other services | 2012 |
| Hamsterley Cafe & Tea Room Ltd | Hospitality | 2019 |
| Hamsterley Forest Ice Cream Kiosk Ltd | Hospitality | 2019 |
| Hanaido Ltd. | Wholesale & retail | 2014 |
| Hansamelie Consulting Ltd | Information & communication | 2018 |
| Happy Homes Cleaning Company Ltd | Administrative & support | 2023 |
| Harbro Supplies Limited | Wholesale & retail | 2000 |
| Harburn Property Investments Ltd | Real estate | 2016 |
| Harehope Quarry Project Limited | Agriculture & fishing | 1999 |
| Harmonics Electrical Limited | Construction | 2022 |
| Harmonics Mechanical Limited | Construction | 2022 |
| Harmonics Renewables Limited | Construction | 2022 |
| Harmony Accounting Limited | Professional & scientific | 2022 |
| Harrann Fabrication Limited | | 1970 |
| Harris-Jones Medical Limited | Wholesale & retail | 2014 |
| Harrison Ground Earthing Limited | Extraterritorial | 2013 |
| Harrison Property & Facility Services Ltd | Construction | 2024 |
| Harry Lambard Coaching Ltd | Other services | 2024 |
| Harry Wilkinson Limited | Extraterritorial | 2016 |
| Haryana Enterprises Ltd | Hospitality | 2025 |
| Hathaway Roofing Holdings Limited | Financial services | 2019 |
| Hawkins Roofing NE Ltd | Construction | 2024 |
| Hawthorn Fields (Rufforth) Management Company Limited | Households | 2024 |
| Hawthorn Leather Company Limited | Wholesale & retail | 2022 |
| Hazeldene Fencing Limited | Construction | 2014 |
| Hdmevents Ltd | Hospitality | 2025 |
| Healey Family Holdings Ltd | Real estate | 2025 |
| Hedley Farm Homes Limited | Construction | 2003 |
| Heico-Cook Defence Ltd | Financial services | 2026 |
| Helen Redhead Consultancy Limited | Public administration | 2025 |
| Hercules Security Limited | Extraterritorial | 2008 |
| Heritage Homes (Durham) Ltd | Real estate | 2015 |
| Herrador Malaga Ltd | Agriculture & fishing | 2018 |
| Hewitt Family Assets Limited | Construction | 2015 |
| HGM Holdings Ltd | Wholesale & retail | 2023 |
| Hidden Story C.I.C. | Education | 2021 |
| High Crane Limited | Agriculture & fishing | 1996 |
| High Doctor Pasture Caravan Park Limited | Hospitality | 2011 |
| High Etherley Kennels Limited | Agriculture & fishing | 2007 |
| High Farm Holiday Park Ltd | Agriculture & fishing | 2014 |
| Hillbeck Trading Limited | Other services | 2019 |
| Hillrise Flats Limited | Agriculture & fishing | 2008 |
| Hilltop Glazing Limited | Construction | 2026 |
| Hiltongate Developments Limited | Real estate | 2008 |
| Hindmarsh Holdings Limited | Real estate | 2017 |
| Hiwa Logistics Limited | Wholesale & retail | 2025 |
| Hiyed CIC | Public administration | 2023 |
| Hiyed UN Ltd | Education | 2025 |
| HJH Events Ltd | Agriculture & fishing | 2023 |
| HLL Limited | Information & communication | 2016 |
| Hobrough Healthcare Limited | Health & social care | 2021 |
| Hoda Leisure Ltd | Hospitality | 2018 |
| Holdforth Fast Fit Centre Limited | Wholesale & retail | 2007 |
| Holdforth Management Company Limited | Real estate | 1999 |
| Holdham Events Limited | Arts & recreation | 2026 |
| Holdham Rail Limited | Administrative & support | 2025 |
| Holdham Rail Solutions Group Limited | Financial services | 2024 |
| Holidays R US Limited | Administrative & support | 2013 |
| Homes by Trafalgar (Sedgefield) Limited | Construction | 2022 |
| Homes by Trafalgar Durham Limited | Construction | 2018 |
| Hong Kong Yummy Ltd | Hospitality | 2025 |
| Honoursboards UK Ltd | Manufacturing | 2021 |
| Hooked in Training and Development Limited | Education | 2026 |
| Hope & Todd Limited | Real estate | 2022 |
| Hops and Dreams (NE) Limited | Hospitality | 2024 |
| Hot Mess Games Ltd | Information & communication | 2015 |
| HPB Plant Hire Ltd | Administrative & support | 2025 |
| HRJ Project Services Ltd | Professional & scientific | 2025 |
| HS Tyres NE Ltd | Wholesale & retail | 2025 |
| HSC Structures Limited | Extraterritorial | 2009 |
| Humble Handyman Services Limited | Construction | 2023 |
| Hunley & Co Limited | Professional & scientific | 2024 |
| Hunter Business Solutions (NE) Ltd | Water & waste | 2022 |
| Hutchinson Land Ltd | Real estate | 2021 |
| Hymas & Hall Limited | Construction | 1985 |
| Hymas and Hymas Trading Ltd | Wholesale & retail | 2021 |
| I Stoker Civils & Groundworks Limited | Construction | 2016 |
| I-Smile Dental Care Ltd | Health & social care | 2025 |
| I.L.H. (Direct Beds) Limited | Wholesale & retail | 2019 |
| IAP Partnership Limited | Administrative & support | 2023 |
| Iceplane Limited | Manufacturing | 2012 |
| ICG Property Limited | Real estate | 2021 |
| Idea Psychology Ltd | Professional & scientific | 2007 |
| Ihcr Limited | Professional & scientific | 2021 |
| IHG Legal Services Limited | Professional & scientific | 2017 |
| Ihomes Control Systems Limited | Construction | 2012 |
| Illumine Dental Limited | Health & social care | 2025 |
| Impact@G Limited | Professional & scientific | 2022 |
| Import Car Parts Limited | Wholesale & retail | 2012 |
| Imprint Art Fair Ltd | Wholesale & retail | 2026 |
| Increment by One Ltd | Information & communication | 2015 |