| Haresby Homes Ltd | Construction | 2007 |
| Hartside Property Investment Company Limited | Real estate | 1964 |
| Haugh Head Holdings Ltd | Real estate | 2020 |
| HD Hot TUB Breaks Ltd | Hospitality | 2020 |
| Hedgehope Limited | Financial services | 2022 |
| Helen Wildsmith Limited | Professional & scientific | 2000 |
| Helios Computing Limited | Information & communication | 1988 |
| Hexham Auction Mart Company,Limited | Agriculture & fishing | 1901 |
| Hexham Day Nurseries Limited | Education | 2019 |
| Hexhamshire Organics Ltd | Extraterritorial | 2011 |
| Highrapid Limited | Real estate | 1990 |
| Hjem Sport Ltd | Administrative & support | 2024 |
| Holland-Sowler Limited | Professional & scientific | 1982 |
| Houses With Halls Ltd | Real estate | 2025 |
| Howick Trustees Limited | Arts & recreation | 1975 |
| Hubbway Group Limited | Professional & scientific | 2026 |
| IAN Law (Builders) Limited | Construction | 2003 |
| IAN Potts & Sons Limited | Agriculture & fishing | 2005 |
| ID Infinity Limited | Wholesale & retail | 2023 |
| IDA Controls Ltd | Manufacturing | 2003 |
| IFF Scaffolding Ltd | Construction | 2024 |
| Images Beauty Studio Limited | Other services | 2003 |
| IN Linea Limited | Information & communication | 1997 |
| Indoor Climate Control Group Ltd | Financial services | 2021 |
| Insight Neurodevelopmental Assessments Ltd | Health & social care | 2025 |
| Interlux Limited | Manufacturing | 1996 |
| Intesym Ltd. | Information & communication | 2001 |
| It's Easy Software Training Limited | Information & communication | 2002 |
| J & D Longlands Ltd | Agriculture & fishing | 2002 |
| J a and K Rowland Limited | Agriculture & fishing | 2006 |
| J a S S Limited | Arts & recreation | 1975 |
| J Herron & SON Limited | Manufacturing | 2003 |
| J. Bradburn (Builders) Limited | Extraterritorial | 1981 |
| J. Craigs Limited | Agriculture & fishing | 1976 |
| J.Bradburn & Company,Limited | Construction | 1924 |
| J.C.& D.C. Short | | 1987 |
| J.E.Bradshaw,Limited | | 1942 |
| J.H. Greenwood & Company Limited | Professional & scientific | 2005 |
| J.R. Bell (Electrical Contractors) Limited | Wholesale & retail | 1981 |
| J.R. Grieves and Company (Embleton) Limited | Wholesale & retail | 1963 |
| J.R.Inkster (Contractors) Limited | Wholesale & retail | 1963 |
| James Cooper & SON (Tyneside) Ltd | Wholesale & retail | 2004 |
| James Robert Hewitson Ltd | Transport & logistics | 2025 |
| Jane Lovett Limited | Wholesale & retail | 2016 |
| Jgarden 888 Ltd | Hospitality | 2019 |
| Joanne Clifford Limited | Health & social care | 2004 |
| Joseph March Limited | Wholesale & retail | 1976 |
| Jusepo Limited | Construction | 1991 |
| Kaas Properties (North) Limited | Real estate | 2003 |
| Kevin Armstrong Limited | Construction | 2007 |
| Kielder Country Sport Limited | Arts & recreation | 2023 |
| Kitkare Ltd | Extraterritorial | 2003 |
| Koyasan Holdings Ltd | Financial services | 2022 |
| L & S E Nielsen Limited | Agriculture & fishing | 2002 |
| L. Dickinson Limited | Health & social care | 2004 |
| LA Cucina Fresca Ltd | Hospitality | 2025 |
| Lane Farm Equestrian Limited | Arts & recreation | 2016 |
| Lane Farm Group Limited | Financial services | 2026 |
| Lathe Jackson Estates Holding Limited | Construction | 2022 |
| LES Belles Limited | Other services | 2004 |
| LFR (Seahouses) Limited | Hospitality | 1989 |
| Lilidorei Licensing Limited | Wholesale & retail | 2025 |
| Lilidorei Media Limited | Information & communication | 2025 |
| Lilidorei Operations Limited | Arts & recreation | 2025 |
| Lindisfarne Limited | Manufacturing | 1975 |
| Lindisfarne Mead Company Limited | Extraterritorial | 2011 |
| Lintonville 130 Limited | Real estate | 2005 |
| Lion Garage (Bedlington) Limited | Hospitality | 1955 |
| Little Angels FUN Club and Nursery Limited | Education | 1999 |
| Littler 180 Ltd | Professional & scientific | 2024 |
| Littler 2024 Ltd | Professional & scientific | 2024 |
| Livingston Care Limited | Health & social care | 1995 |
| Logistic Solutions Ltd | Professional & scientific | 2024 |
| Logotech Display Solutions Limited | Manufacturing | 2002 |
| Looks Natural Wildlife Consultancy Limited | Professional & scientific | 2025 |
| Luna Submarine Limited | Information & communication | 2006 |
| Lynx Taxis (Blyth) Limited | Arts & recreation | 1996 |
| M.J. Hickey Plant Hire & Contracts Limited | Construction | 2003 |
| M.Marshall and Sons Limited | Construction | 2002 |
| M.W. Herdman Forestry Solutions Limited | Agriculture & fishing | 2008 |
| MA Design Engineering Ltd | Professional & scientific | 2015 |
| Madeha Limited | Hospitality | 2002 |
| Magnatech Electronics Limited | Manufacturing | 2005 |
| Mark Westerby Limited | Professional & scientific | 2002 |
| Martins the Printers Limited | Manufacturing | 1992 |
| Maryport Boat Company Limited | Manufacturing | 1992 |
| Masala Tandoori Limited | Hospitality | 2006 |
| Matfen Hall Limited | Professional & scientific | 2006 |
| Maughan Holdings Limited | Real estate | 2022 |
| Maughan Microcomputers Limited | Wholesale & retail | 2007 |
| Maya Direct Limited | Extraterritorial | 2000 |
| Mbott Design Limited | Professional & scientific | 2007 |
| Mcli Ltd | Professional & scientific | 2013 |
| Medical Food Limited | Extraterritorial | 2003 |
| Michael Guthrie Developments Limited | Construction | 2002 |
| Milburn Stores Ltd | Wholesale & retail | 2005 |
| Mindrum Farming Company Limited | Agriculture & fishing | 1971 |
| Mindrum Properties Limited | Real estate | 1955 |
| Mitford Health Limited | Extraterritorial | 1998 |
| Modern Architectural Stone Limited | Professional & scientific | 2007 |