| J. Jackson Properties Limited | Real estate | 2004 |
| J.A.B Foods Ltd | Hospitality | 2023 |
| J.A.G. Solutions Limited | Transport & logistics | 2010 |
| J.J.Hardy & Sons Limited | Manufacturing | 1922 |
| J.Lings Technical Solutions Ltd | Construction | 2017 |
| J.P.Barton Hv/Lv Ltd | Construction | 2025 |
| J.W. Hobbs Limited | | 1968 |
| J.Y. Engineering Limited | Professional & scientific | 1997 |
| J3 Property Development Limited | Construction | 2014 |
| J3NM Ltd | Real estate | 2023 |
| JA Bell Property Investments Ltd | Real estate | 2024 |
| Jack Nixon Inspections Ltd | Arts & recreation | 2025 |
| Jack of Hearts CIC | Arts & recreation | 2021 |
| Jackson & Copeland Limited | Real estate | 2006 |
| Jackson Construction and Civil Engineering Services Ltd | Construction | 2024 |
| Jackson NDT Services Ltd | Professional & scientific | 2013 |
| Jackwoodford Limited | Construction | 2014 |
| Jacon Engineering Ltd | Professional & scientific | 2026 |
| Jacra Development Limited | Real estate | 2025 |
| Jacra Group Limited | Financial services | 2026 |
| Jade Building Management Systems Limited | Construction | 2002 |
| JAF Properties (NE) Ltd | Real estate | 2021 |
| Jaig Services Ltd | Health & social care | 2022 |
| JAJ Sports Management Ltd | Arts & recreation | 2019 |
| James David Hearing Care Ltd | Health & social care | 2023 |
| Jamie Fleming Risk Management Ltd | Professional & scientific | 2024 |
| Jamos Property Services Ltd | Households | 2025 |
| Jarvis Coatings Inspection Limited | Professional & scientific | 2018 |
| Jarvis Engineering Services Limited | Professional & scientific | 2025 |
| JAX Story C.I.C. | Education | 2019 |
| Jaxons Kingdom Ltd | Hospitality | 2026 |
| Jaya Top Shop Limited | Wholesale & retail | 2023 |
| JB Gold&Bullion Ltd | Wholesale & retail | 2026 |
| JB Jointing Services Ltd | Construction | 2018 |
| JB Memorabilia Ltd | Wholesale & retail | 2025 |
| JB Project Solutions Limited | Real estate | 2023 |
| JB20 Property Limited | Real estate | 2026 |
| JBK Insulation Ltd | Energy | 2020 |
| Jbpp Ltd | Real estate | 2015 |
| JC Cables Ltd | Construction | 2020 |
| JC Commercial Services Limited | Professional & scientific | 2024 |
| JC Haulage (Hartlepool) Limited | Transport & logistics | 2016 |
| JC4 Financial Limited | Financial services | 2023 |
| JCD Electrical Contractors Ltd | Construction | 2025 |
| JCG E/I Limited | Construction | 2015 |
| JCM Industrial Services Ltd | Manufacturing | 2024 |
| JCS Contractors (Northern) Ltd | Construction | 2000 |
| JD Courier Services Ltd | Transport & logistics | 2008 |
| Jdengineeringservicesltd Limited | Professional & scientific | 2022 |
| JDM Earth Limited | Construction | 2014 |
| JE Giles Limited | Professional & scientific | 2008 |
| JE Property Lettings Ltd | Real estate | 2020 |
| Jefs Property Ltd | Real estate | 2025 |
| Jengsafe Ltd | Construction | 2023 |
| Jennifer Logistics Ltd | Transport & logistics | 2024 |
| Jennjo Ltd | Extraterritorial | 2014 |
| Jewson Communications Ltd | Information & communication | 2019 |
| Jewson Consulting Ltd | Professional & scientific | 2023 |
| JFW Physio Rooms Ltd | Other services | 2023 |
| Jgib Ltd | Professional & scientific | 2025 |
| JGL Inspection Services Ltd | Professional & scientific | 2023 |
| JH Auto Developments Ltd | Wholesale & retail | 2020 |
| JH Aviation Training Limited | Administrative & support | 2022 |
| JH Coaching Ltd | Education | 2021 |
| JH11 Motorsport Ltd | Wholesale & retail | 2023 |
| JHA Construction Limited | Construction | 2012 |
| Jhenn Properties Limited | Real estate | 2025 |
| JHI Offshore Services Ltd | Professional & scientific | 2022 |
| JHM Pipeline Services Ltd | Construction | 2017 |
| Jhvd Plating & Fabrication Services Ltd | Manufacturing | 2017 |
| Jimco Group Ltd | Information & communication | 2025 |
| Jjaccomadation Ltd | Wholesale & retail | 2025 |
| JJB a Services Ltd | Water & waste | 2023 |
| JJB Face Fitting Services Ltd | Construction | 2026 |
| JJD Access Solutions Ltd | Construction | 2024 |
| Jjrh Group Limited | Financial services | 2026 |
| JK Lawson Property Management Ltd | Real estate | 2017 |
| JK Management Consultancy Limited | Professional & scientific | 2021 |
| JKB Wind Limited | Professional & scientific | 2024 |
| JKF Clothing Limited | Wholesale & retail | 2004 |
| JL Electrical Services Ltd | Construction | 2025 |
| JL Jeffries Logistics Ltd | Transport & logistics | 2025 |
| JL Plating Services Limited | Manufacturing | 2025 |
| JLD Healthcare Consultancy Limited | Professional & scientific | 2023 |
| JLK Engineering Ltd | Professional & scientific | 2023 |
| JLN Haulage and Storage Limited | Administrative & support | 2017 |
| JLP Properties NE Limited | Real estate | 2025 |
| JM Globis Ltd | Wholesale & retail | 2026 |
| JM Property Services (NE) Ltd | Real estate | 2025 |
| JM Send Services Ltd | Education | 2024 |
| JMB Safety Ltd | Professional & scientific | 2025 |
| JMB SI Ltd | Administrative & support | 2025 |
| JMC (NE) Building Services Ltd | Construction | 2022 |
| JMC Developments NE Limited | Real estate | 2025 |
| JMH Property Developments Ltd | Other services | 2024 |
| JMJ Fibre Networks Limited | Construction | 2022 |
| JML Coating Limited | Professional & scientific | 2013 |
| JMS Plumbing and Heating Limited | Construction | 2024 |
| JN2 Enterprises Ltd | Financial services | 2022 |
| JOE Wilson Spraying & Blasting Specialist Ltd | Construction | 2025 |