| Jamie Cook Haulage Ltd. | Airdrie | 2011 |
| Jamroc Engineering Ltd | Yarm | 2010 |
| Jamyn Limited | Inverurie | 2021 |
| Jana International Ltd | Omagh | 2024 |
| Janaca UK Limited | Aberdeen | 2025 |
| Jangada Mines PLC | London | 2015 |
| Janssens Smeets (Netherlands) Co., Ltd | Coventry | 2025 |
| Japan Gangshan Chemical Ltd | West Midlands, England | 2023 |
| Japan Longyehuacheng Zhushehuishe Limited | Stafford | 2025 |
| Japan Sakurai Chemical Co., Limited | West Midlands, England | 2026 |
| Japan Seiwa Kampo Co., Ltd | Cardiff | 2025 |
| Japan Yezhuang Fertilizer Ltd | Cambridge | 2023 |
| Jarl Marine Limited | London | 2025 |
| Jason Protheroe Ltd | Forres | 2019 |
| Java Energy (UK) Limited | London | 2020 |
| Javed DIN Contracting Ltd | Arbroath | 2024 |
| Javelin Global Commodities (UK) Ltd | London | 2015 |
| Javelin Marketing and Sales (UK) Ltd | London | 2022 |
| Javelin Marketing and Trading (UK) Ltd | London | 2017 |
| JAW Well Services Ltd | Peterculter | 2024 |
| Jaws High Voltage Solutions Limited | Lowestoft | 2024 |
| Jayflex (Aggregates) Ltd | London | 1997 |
| Jayteeco Limited | Aberdeen | 1997 |
| JB Rope Access Services Ltd | Peterhead | 2024 |
| JB10 Solutions Ltd | Kilmaarnock | 2022 |
| Jbgeological Services Limited | Penarth | 2014 |
| Jbm.Ntd Ltd | Dumfries | 2025 |
| JBS Power Limited | Peterhead | 2019 |
| JC Associates OIL and GAS Safety Ltd | Stirling | 2024 |
| JC Technical Services Limited | Sheffield | 2015 |
| JCC 1977 Services Ltd | Montrose | 2025 |
| Jccswelding Ltd | Redcar | 2016 |
| Jcfm Services Ltd | Newton Aycliffe | 2016 |
| JCJ Minerals Ltd | Doncaster | 2019 |
| Jcunningham Rope Access Ltd | Stirling | 2017 |
| JCW Engineering Consultants Limited | High Wycombe | 2014 |
| JCW Scientific Ltd | Kenilworth | 2023 |
| Jcws Engineering Limited | Banff | 2018 |
| JD Alpha Services Limited | Leicester | 2013 |
| JD Energy Solutions Limited | Aberdeen | 2012 |
| JD Geoconsultancy Limited | Wetherby | 2024 |
| JD Geoscience Limited | Derby | 2016 |
| JD Lifting Solutions Ltd | Grangemouth | 2025 |
| JD Offshore (Bolting Services) Ltd. | Hebburn | 2014 |
| Jdas Enterprises Ltd | Magherafelt | 2022 |
| JDB Energy Services Limited | Stockton On Tees | 2025 |
| JDC Rigging Lifting & Engineering Services Ltd | London | 2025 |
| JDT Services Ltd | Montrose | 2016 |
| JDV Subsea Ltd | Montrose | 2016 |
| Jebco Seismic (UK) Limited | West Malling | 1991 |
| JEE Limited | Tonbridge | 1998 |
| Jeeffrancoisservices Ltd | London | 2021 |
| Jeenius Limited | Tonbridge | 2012 |
| JEM Star Consultancy Limited | Insch | 2021 |
| Jemika Ltd | Glasgow | 2025 |
| Jenex Limited | Great Yarmouth | 1996 |
| Jenico Services Limited | Aberdeen | 2020 |
| JEO Wells Ltd | Dundee | 2019 |
| Jersey Petroleum Ltd | London | 2008 |
| Jersey V&C Ltd | London | 2017 |
| Jesco Inspection Ltd | Newcastle Upon Tyne | 2019 |
| Jessups (Lime Productions) Limited | Sevenoaks | 1935 |
| JET Pumps UK Ltd | Ammanford | 1997 |
| Jete NDT Ltd | Carrickfergus | 2021 |
| Jetex Petroleum Ltd | London | 2012 |
| JEX Geoconsulting Limited | London | 2020 |
| Jeylee Holdings Limited | Wolverhampton | 2021 |
| JF Blanchard Electrical Services Ltd | Banff | 2014 |
| JG Marsden Ltd | Arbroath | 2012 |
| JH Cable Limited | Great Yarmouth | 2023 |
| JH Ward Ltd | Cleethorpes | 2025 |
| Jhal Engineering Ltd | Coatbridge | 2018 |
| Jhgs Rigging Ltd | Wirral | 2022 |
| JIB Great Yarmouth Limited | Lowestoft | 2023 |
| Jigsaw Logistics & Materials Ltd | Ellon | 2018 |
| Jimaj Energy Services Limited | Edinburgh | 2012 |
| Jimtek Ltd | Lowestoft | 2012 |
| Jing Knack Co., Ltd | Beckenham | 2021 |
| JJ Offshore Ltd | London | 2023 |
| JJP Technical Services (UK) Ltd | Arbroath | 2016 |
| JJS Minerals Co. Limited | Oxford | 2009 |
| JJS Minerals INT. Limited | Thame | 2014 |
| JJS Resources Co Ltd | Thame | 2023 |
| JJT Projects Ltd | Salisbury | 2020 |
| JK Geological Services Limited | Southsea | 2012 |
| JK New Build Yaser Ltd | London | 2014 |
| JK Offshore Ltd | London | 2013 |
| JKR Quarries and Concrete Products Ltd | Ellon | 2020 |
| JKW Offshore Ltd | Buckie | 2019 |
| JKX Georgia Ltd | London | 2002 |
| JKX Services Limited | London | 1994 |
| JL Industrial Consultants Ltd | Brechin | 2025 |
| Jl-Enterprise International Ltd | Manchester | 2023 |
| Jldh Telecommunications and Rope Access Limited | Kirkby In Cleveland | 2019 |
| JLJ Consultants Ltd | Montrose | 2016 |
| JLM Plant Hire Limited | London | 2020 |
| Jlsh Industrial Solutions Ltd | Bedlington | 2026 |
| JM Bliss Ltd | Birmingham | 2014 |
| JM Drilling Ltd | Montrose | 2007 |
| JM Global Marine Limited | Dundee | 2011 |