| J Walton Ltd | Energy | 2019 |
| J&R Express Transport Ltd | Transport & logistics | 2021 |
| J&R Properties & Lettings Limited | Real estate | 2024 |
| J-Mar Limited | Construction | 2010 |
| J. Donnelly Agricultural Contractor Limited | Agriculture & fishing | 2018 |
| J. O. Straughan & Co. Limited | Agriculture & fishing | 1986 |
| J. W. Peters Limited | Other services | 2015 |
| J.O.S Fire Safety Ltd | Public administration | 2024 |
| J.W.Thompson(Whitefield)Limited | Agriculture & fishing | 1959 |
| Jack Evan Auld Limited | Extraterritorial | 2025 |
| Jack Small Ltd | Construction | 2019 |
| Jacksons Jewellers Ltd | Wholesale & retail | 2009 |
| JAG Technical Services Limited | Professional & scientific | 2020 |
| JAM Roly Poly Ltd | Hospitality | 2025 |
| James Autos 1 Ltd | Wholesale & retail | 2023 |
| James Darren Liddle Ltd | Professional & scientific | 2022 |
| James Edmondson Building Maintenance Ltd | Construction | 2018 |
| James Lawrence Limited | Professional & scientific | 2024 |
| James Mcewan Limited | Construction | 2026 |
| James Nicholson Heating Limited | Construction | 2023 |
| James Ryan Brady Ltd | Administrative & support | 2023 |
| James White Brickwork Limited | Construction | 2018 |
| Jamesturner.Work Ltd | Professional & scientific | 2026 |
| Jardine Residential Ltd | Real estate | 2021 |
| JAS Contracting Services Ltd | Professional & scientific | 2016 |
| JAW Games Ltd | Information & communication | 2025 |
| JB Microscopes Limited | Manufacturing | 2011 |
| Jbedwell Ltd | Professional & scientific | 2021 |
| JC Wave Tech Ltd | Professional & scientific | 2024 |
| JCO Property Investment Ltd | Real estate | 2025 |
| Jcod Living Ltd | Manufacturing | 2025 |
| Jcrogerson.Electrical Ltd | Construction | 2019 |
| JD Recruitment Group Ltd | Administrative & support | 2019 |
| JD Wealth Ltd | Financial services | 2026 |
| Jeannie Ashten Ltd | Arts & recreation | 2010 |
| Jemco Consultancy Limited | Professional & scientific | 2015 |
| Jennifer Godwin Ltd | Health & social care | 2018 |
| Jfjp Performance Ltd | Wholesale & retail | 2016 |
| Jgjb Properties Limited | Real estate | 2024 |
| JH Pipeline Services Limited | Manufacturing | 2015 |
| JH Technical Services Ltd | Professional & scientific | 2023 |
| Jireh Engineering Limited | Professional & scientific | 2017 |
| JK Mouat & SON Limited | Agriculture & fishing | 2024 |
| JM Mccracken & Sons Ltd | Transport & logistics | 2022 |
| JMO Signs Ltd | Construction | 2025 |
| JMS JR Scaffolding Limited Limited | Construction | 2025 |
| JMS Painting and Decorating Limited | Construction | 2026 |
| JO Robinson Ltd | Real estate | 2024 |
| JO Storie Design Ltd | Manufacturing | 2025 |
| John Gerard Hair Design Limited | Other services | 2006 |
| John J Astley Limited | Arts & recreation | 2013 |
| John P Cooper Ltd | Wholesale & retail | 2019 |
| JON Tweddell Planning Ltd | Administrative & support | 2010 |
| Jordann Dixon Ltd | Hospitality | 2023 |
| Joyce Properties Ltd | Real estate | 2021 |
| JP Northern Limited | Professional & scientific | 2023 |
| Jpbm Consulting Limited | Professional & scientific | 2017 |
| JT Roofing Systems Ltd | Construction | 2017 |
| JTB Builders Ltd | Construction | 2012 |
| Jtek Services Limited | Professional & scientific | 2020 |
| Judge D Liddle Ltd | Financial services | 2023 |
| Julie Elliott REC 2 REC Ltd | Administrative & support | 2026 |
| Jumboo Ltd | Extraterritorial | 2023 |
| Junior ALL Stars Ltd | Health & social care | 2017 |
| Just Taxis Morpeth Ltd | Transport & logistics | 2019 |
| Justin James Auld Limited | Extraterritorial | 2025 |
| Justin James Reynolds Ltd | Extraterritorial | 2025 |
| Justmachining Limited | Professional & scientific | 2021 |
| JW Donovan Logistics Ltd | Transport & logistics | 2025 |
| JX Tanning Studios Ltd | Other services | 2005 |
| K H Consulting Ltd | Professional & scientific | 2023 |
| K N L Builders & Home Improvements Ltd | Construction | 2024 |
| K9 Room Outdoors & Shop Ltd | Wholesale & retail | 2024 |
| Kabl Services Ltd | Professional & scientific | 2019 |
| KAL Group Ltd | Wholesale & retail | 2018 |
| Kaliander Developments Ltd | Construction | 2025 |
| Karenic Communications Limited | Professional & scientific | 1996 |
| Kaski Ltd | Wholesale & retail | 2026 |
| Kastia Limited | Construction | 2024 |
| Kate Simpson Fine Art Limited | Wholesale & retail | 2022 |
| Kathryn Kent Residential Limited | Real estate | 2022 |
| KCE Van ZYL Properties Ltd | Real estate | 2019 |
| Keel ROW Management Company Limited | Real estate | 2003 |
| Keen on Solutions Limited | Administrative & support | 2004 |
| Keith Walker Developments Limited | Construction | 2011 |
| Keithmiller Ltd | Construction | 2025 |
| Ken's Jobs. Commercial Vehicle Repairs Ltd | Wholesale & retail | 2024 |
| Kenn Toft Limited | Education | 2022 |
| Kerala Connections Limited | Administrative & support | 2020 |
| Kevin Scott Construction Consultancy Limited | Administrative & support | 2018 |
| KG DRY Wall Interiors Limited | Construction | 2020 |
| KGC Brands Ltd | Wholesale & retail | 2026 |
| Khew Ltd | Hospitality | 2024 |
| Kidland Estates Ltd | Real estate | 2015 |
| Kielder Forest Products Ltd | Agriculture & fishing | 1992 |
| Kilcar IT Consulting Limited | Information & communication | 2012 |
| King & Coats Limited | Professional & scientific | 2021 |
| Kits House Ltd | Real estate | 2025 |
| Kk-Electrical Contracting Ltd | Construction | 2025 |
| Knect Broadband Ltd | Information & communication | 2021 |