| J&B Sunderland Community Interest Company | Health & social care | 2021 |
| J.A. Mcmurchie (Meat) Limited | Wholesale & retail | 1975 |
| JAB Landscapes & Groundworks Limited | Construction | 2018 |
| JAB Properties Ltd | Real estate | 2022 |
| Jack Gething Logistics Ltd | Transport & logistics | 2025 |
| Jack Gray Accountancy Services Limited | Professional & scientific | 2020 |
| Jack-James Holdings Ltd | Real estate | 2022 |
| Jacks Delivery Service Ltd | Transport & logistics | 2026 |
| Jackson & O'Leary Catering Limited | Hospitality | 2009 |
| Jacwicks Designs Limited | Manufacturing | 2018 |
| Jake (NE) Ltd | Hospitality | 2026 |
| Jake Keelin Ltd | Manufacturing | 2026 |
| Jalat Properties Ltd | Real estate | 2024 |
| James White Joinery Ltd | Construction | 2022 |
| Jamie Stockdale Roofing Limited | Construction | 2025 |
| Jangali Foods Ltd | Hospitality | 2020 |
| Janine Hegarty Bell Limited | Real estate | 2022 |
| Janine Hegarty Bell Property Services Limited | Real estate | 2024 |
| Jarrow Technical Services Ltd | Construction | 2018 |
| Javelin Content Management Ltd | Information & communication | 2023 |
| JAY & ARY Ltd | Real estate | 2021 |
| Jayhan Property Management Limited | Real estate | 2025 |
| Jayhan Tech Limited | Information & communication | 2023 |
| JB GAS Services (N E) Limited | Other services | 2013 |
| JB Insulation Services Ltd | Construction | 2025 |
| JBM Waste Management Ltd | Construction | 2025 |
| JC Blades Ltd | Professional & scientific | 2021 |
| JC Management Services Ltd | Manufacturing | 2023 |
| JC10 Projects Ltd | Construction | 2026 |
| Jcct (Advisory) Limited | Professional & scientific | 2024 |
| Jcpv Ltd | Real estate | 2025 |
| Jd'Z Car & Commercial Specialist Body Repairs Ltd | Wholesale & retail | 2019 |
| JDC Media Productions Limited | Wholesale & retail | 2007 |
| Jeff MAC Holdings Limited | Wholesale & retail | 2015 |
| JEM Energy NE Limited | Extraterritorial | 2025 |
| Jenks Recovery and Transport Ltd | Transport & logistics | 2026 |
| Jessmmusic Ltd | Information & communication | 2025 |
| Jewellery Queen Ltd | Wholesale & retail | 2025 |
| JGM Electrical Services Ltd | Construction | 2017 |
| JH Bespoke Joinery Ltd | Construction | 2025 |
| JH Commercial Management Limited | Administrative & support | 2017 |
| JJD Group Ltd | Other services | 2025 |
| Jjjgc Properties (NE) Ltd | Real estate | 2023 |
| JJM Property Solutions NE Ltd | Real estate | 2024 |
| Jjr's Lifting Operations Limited | Manufacturing | 2025 |
| JJT Properties Limited | Real estate | 2002 |
| JL Better Lighting Ltd | Wholesale & retail | 2019 |
| JL Mechanical and Electrical Services Limited | Professional & scientific | 2007 |
| JLE Garden Maintenance NE Ltd | Professional & scientific | 2026 |
| JLW Property Management Limited | Real estate | 2025 |
| JMG Groundworks Limited | Construction | 2023 |
| Jmja Limited | Professional & scientific | 2013 |
| Jmkitchens Limited | Construction | 2026 |
| Joanne Angus Limited | Administrative & support | 2016 |
| Jobs With Purpose Limited | Professional & scientific | 2021 |
| John Buck Estates Ltd | Real estate | 2025 |
| John Buck Property Ltd | Real estate | 2018 |
| John Howard Assessments Limited | Education | 2004 |
| Jordan Property Improvements Ltd | Construction | 2026 |
| JOS North East Limited | Administrative & support | 2015 |
| JRA Medical Supplies Ltd | Health & social care | 2017 |
| JRH Construction Solutions Ltd | Construction | 2019 |
| Just Automotive Ltd | Wholesale & retail | 2018 |
| Just MAG Limited | Wholesale & retail | 2024 |
| Just Pristine CIC | Health & social care | 2023 |
| Jvel Holdings Limited | Real estate | 2020 |
| JW Building Supplies Ltd | Wholesale & retail | 2025 |
| Jwparish Ltd | Energy | 2018 |
| K & R Hunter Metal Recycling Ltd | Transport & logistics | 2025 |
| K Construction NE Ltd | Construction | 2026 |
| K MCD Consultants Ltd | Administrative & support | 2016 |
| K O B Holdings Ltd | Construction | 2024 |
| K.M. Electrical Services Limited | Construction | 2004 |
| Kandola Properties NE Limited | Real estate | 2023 |
| Kanestubbs Ltd | Wholesale & retail | 2025 |
| Kashlee IT Consultancy Ltd | Information & communication | 2025 |
| Kaya Cutz Ltd | Other services | 2025 |
| Kazthetics Aesthetics Ltd | Other services | 2024 |
| KB Tyres (N E ) Limited | Wholesale & retail | 2004 |
| Kbcctv Solutions Ltd | Information & communication | 2023 |
| KBG Limited | Hospitality | 2024 |
| KC International Transport Ltd | Transport & logistics | 2026 |
| KCL Property Holdings Ltd | Transport & logistics | 2025 |
| KCL Transport Ltd | Transport & logistics | 2023 |
| Kelltech.Uk Holdings Ltd | Financial services | 2024 |
| Kelltech.Uk Security & Facilities Services Ltd | Administrative & support | 2023 |
| Keva Nails and Beauty DH4 Ltd | Other services | 2026 |
| Key Property Manager Limited | Households | 2019 |
| KG Project Support Services Limited | Professional & scientific | 2021 |
| Khan's Fast FRY Ltd | Hospitality | 2025 |
| Khaven Ltd | Wholesale & retail | 2025 |
| Kidz Closet Ltd | Wholesale & retail | 2025 |
| Kindly Earth Herrington Limited | Other services | 2022 |
| Kindred Vault Ltd | Health & social care | 2025 |
| King Commercial Services Limited | Professional & scientific | 2016 |
| King Sports Agency Ltd | Arts & recreation | 2019 |
| Kingfisher Sheeting and Cladding Limited | Construction | 2022 |
| Kings Properties (Sunderland) Limited | Households | 2026 |
| KJC Services Ltd | Manufacturing | 2016 |
| KJK Data Ltd | Other services | 2004 |