| Jomast 3 Limited | Professional & scientific | 2012 |
| Jomast 4 Limited | Real estate | 2012 |
| Jomast Accommodation Limited | Real estate | 1969 |
| Jomast Developments Limited | Construction | 1978 |
| Jomast Estates Limited | Professional & scientific | 1974 |
| Jomast Finance Limited | Professional & scientific | 2012 |
| Jomast Hotels Limited | Professional & scientific | 2012 |
| Jomast Limited | Financial services | 2012 |
| Jonathan Hart Limited | Professional & scientific | 2013 |
| Jones and Jones Management LLP | | 2019 |
| Jones Asset Management Ltd | Financial services | 2018 |
| Jones Estate Agents and Mortgage Brokers Ltd | Real estate | 2010 |
| JOS North East Group Limited | Administrative & support | 2022 |
| Josap Holdings Limited | Financial services | 2025 |
| Josarajen Limited | Wholesale & retail | 1995 |
| Joseph James (IAS) Ltd | Professional & scientific | 2021 |
| Josh Walsh Ltd | Construction | 2025 |
| Joslin Rhodes Lifestyle Financial Planning Limited | Financial services | 2007 |
| Joulevault Ltd | Professional & scientific | 2023 |
| JPB Services Ltd | Professional & scientific | 2014 |
| JPC International Ltd | Financial services | 2023 |
| Jpci Ltd | Mining & quarrying | 2026 |
| JPD Home Improvements Ltd | Construction | 2019 |
| JPL OIL & GAS Services Ltd | Construction | 2024 |
| JPL Project Services Ltd | Professional & scientific | 2024 |
| JPM Solutions Ltd | Professional & scientific | 2025 |
| JPN Complete Services Limited | Administrative & support | 2014 |
| JPS Welding Services Ltd | Manufacturing | 2026 |
| Jpwelding Limited | Construction | 2018 |
| JRC Electrical Ltd | Professional & scientific | 2014 |
| JRD Electrical & Instrumentation Limited | Manufacturing | 2017 |
| Jrfcomp Limited | Professional & scientific | 2020 |
| JRJ Plumbing Ltd | Construction | 2022 |
| Jrmlittlefair Ltd. | Real estate | 2017 |
| JRN Electrical Design Limited | Administrative & support | 2014 |
| Jross Contracting Ltd | Manufacturing | 2025 |
| JRW Inspections Ltd | Professional & scientific | 2013 |
| JS & MF LMT Ltd | Hospitality | 2023 |
| JSA Pubs Limited | Hospitality | 2018 |
| JSC Engineering Ltd | Construction | 2017 |
| JSL Tunstall Consulting Limited | Professional & scientific | 2015 |
| Jsropeaccess Limited | Construction | 2025 |
| JSV Site Services Ltd | Administrative & support | 2025 |
| JT Building Solutions Ltd | Construction | 2021 |
| JT Construction Ltd | Energy | 2010 |
| JT Development Enterprises Ltd | Real estate | 2022 |
| JT Effect Limited | Professional & scientific | 2016 |
| JT Property Branch Ltd | Real estate | 2023 |
| JTD Marine Limited | Construction | 2025 |
| JTD Site Services Limited | Manufacturing | 2019 |
| JTP Engineering Limited | Professional & scientific | 2025 |
| Jubilee Church Teesside | Other services | 1999 |
| Jude Chijioke Limited | Health & social care | 2023 |
| Judge Sampson Limited | Manufacturing | 2013 |
| Juicy Marketing & Design Limited | Professional & scientific | 2019 |
| Jules Barron Photography Ltd | Professional & scientific | 2024 |
| July Cleaning Ltd | Administrative & support | 2025 |
| Juma Corporation Ltd | Transport & logistics | 2011 |
| Junction Properties (North East) Ltd | Real estate | 2020 |
| Junction Properties(Norton) Ltd | Real estate | 2025 |
| Junifet Ventures Ltd | Wholesale & retail | 2026 |
| Juno Hire Limited | Administrative & support | 2017 |
| Jupiter Hotels Wetherby Limited | Administrative & support | 2011 |
| Just Medico-Legal Reports Ltd | Health & social care | 2019 |
| Just Money UK Limited | Financial services | 2012 |
| Just Williams Sales Academy Limited | Education | 2021 |
| Justice First Limited | Health & social care | 2006 |
| JVC Engineering Ltd | Professional & scientific | 2025 |
| JVG Logistics Limited | Transport & logistics | 2025 |
| JW Electrical Services (Thornaby) Ltd | Professional & scientific | 2022 |
| JW Plastering Services Ltd | Construction | 2025 |
| JW Trade Solution Ltd | Other services | 2024 |
| JWC Stocks Limited | Financial services | 2026 |
| JWD Consulting Ltd | Health & social care | 2024 |
| Jwmotorworks Limited | Wholesale & retail | 2011 |
| JWP Electrics Limited | Construction | 2023 |
| JX Rising Sun Limited | Hospitality | 2021 |
| JY Mart Trading Limited | Wholesale & retail | 2024 |
| JZL Solutions Limited | Information & communication | 2006 |
| JZR Valeting Limited | Administrative & support | 2025 |
| K a W Properties Limited | Real estate | 2020 |
| K Brown Wind Services Ltd | Construction | 2025 |
| K Carter Consulting Ltd | Professional & scientific | 2025 |
| K Green Property Management Limited | Real estate | 2025 |
| K T L Renewables Ltd | Construction | 2026 |
| K U Designs Ltd | Construction | 2024 |
| K&H Access Ltd Ltd | Construction | 2022 |
| K&R Corporations Ltd | Real estate | 2025 |
| K&R Health Group Ltd | Health & social care | 2026 |
| K. C. Planning OIL & GAS Ltd | Construction | 2017 |
| K.R. Maintenance Limited | Manufacturing | 2011 |
| K1 Scaffolding KM Ltd | Construction | 2025 |
| KAD Enterprises Limited | Real estate | 2020 |
| Kaijo Holdings Ltd | Financial services | 2025 |
| Kaijo North Consulting Ltd | Financial services | 2024 |
| Kaistyle Ltd | Wholesale & retail | 2022 |
| KAL EL Properties Ltd | Real estate | 2023 |
| Kaldani Builders Ltd | Construction | 2013 |
| Kaldani Properties Limited | Real estate | 2017 |
| Kaldani Real Estate Limited | Construction | 2022 |