| Mycorp Energy Limited | London | 2024 |
| Mythe Systems Limited | Frome | 2012 |
| Mytholm Stone Sales Limited | Leeds | 1951 |
| Mytilus Limited | Bradford-On-Avon | 2017 |
| N & R Services Limited | Bedfordshire | 1996 |
| N a Pipe & Survey Services Ltd | Peterhead | 2013 |
| N G Jackson Consulting Ltd | Aberdeen | 2023 |
| N G R Land Development Limited | Birmingham | 1994 |
| N R D Limited | Aberdeenshire | 1997 |
| N&A NE Ltd | Newcastle Upon Tyne | 2023 |
| N&G Mining Limited | Windsor | 2022 |
| N&J Automation Limited | Glossop | 2023 |
| N&L Consult Ltd | York | 2025 |
| N-Sea UK Limited | Milton Keynes | 2021 |
| N.E.I. (Edzell) Limited | Brechin | 2013 |
| N.F.C. Consultancy Services Ltd | Beccles | 2004 |
| N2 OIL and GAS Ltd | Great Yarmouth | 2011 |
| N7 Recycling Ltd | Goole | 2022 |
| NA Mara Innovations Ltd | Peterhead | 2023 |
| NAB Safety Ltd | Arbroath | 2016 |
| Nachingwea U.K. Limited | London | 2014 |
| Nairn Inspection Ltd | Nairn | 2019 |
| NAJ Antipodes Ltd | London | 2016 |
| Nalita Transport and Logistics Ltd | Milton Keynes | 2023 |
| Nama Energy Group PLC | London | 2026 |
| Nama Energy Ltd | Worcester Park | 2025 |
| Namimine Group Ltd | Birmingham | 2023 |
| Namsa Limited | Turriff | 2009 |
| Namurian Geological Services Limited | Radcliffe | 2013 |
| Naneek Limited | Magherafelt | 2023 |
| Nanhoron Granite Quarry (2014) Ltd | Pwllheli | 2014 |
| Nano Ltd | Airdrie | 2021 |
| Nasa Comercial DE Nascimento Alberto UK Limited | Chesham | 2016 |
| Nascon Aggrigates Ltd | Coventry | 2023 |
| Nashscope Fishing Limited | Pembrokeshire | 1985 |
| National Oilwell Varco UK Limited | Stonehouse | 1966 |
| Nationwide Crushing Services Limited | London | 2021 |
| Nationwide Materials Limited | Coventry | 2025 |
| Nativo Resources PLC | London | 2005 |
| Natuna UK (Kakap 2) Limited | London | 1995 |
| Natural Energy Resources (OIL & GAS) Limited | Norwich | 2026 |
| Natural Resource Charter Limited | London | 2011 |
| Natural Stone Baths Ltd | Westcliff-On-Sea | 2021 |
| Natural Stone Direct (Cumbria) Limited | Brampton | 2009 |
| Naughty Fish Ltd | | 2006 |
| Nauticuas Inspection & Survey Limited | Ruthin | 2017 |
| Naviera DEL Caribe Limited | London | 2011 |
| Navigator Terminals Midco Limited | Grays | 2015 |
| Navigator Terminals North Tees Limited | Grays | 2015 |
| Navitas Petroleum Africa Ltd | London | 2026 |
| Navitas Petroleum Atlantic Limited | London | 2025 |
| Navitas Petroleum Development and Production Ltd | London | 2012 |
| Navitas Petroleum Guyana Ltd | London | 2026 |
| Navitas Petroleum Limited | London | 2013 |
| Navitas Petroleum Philippines Limited | London | 2022 |
| Nayles Barn Quarry Limited | Chipping Norton | 2021 |
| Naylor Technical Solutions Ltd. | Barnsley | 2000 |
| Naylor, Benzon & Co. Limited | Tenterden | 1979 |
| Nazteq Industries Ltd | Leicester | 2010 |
| Nbdenergy Ltd | Lowestoft | 2026 |
| NCB Subsea Ltd | Ellon | 2025 |
| Ncdf UK Limited | Enfield | 2013 |
| NCE Drilling Consultants Limited | Halesworth | 2015 |
| Ncrd Nanoparticles Limited | London | 2025 |
| ND Joint Integrity Services Limited | Sunderland | 2019 |
| ND3 Ltd | Plymouth | 2015 |
| NDT Services KJD Limited | Aberdeen | 2019 |
| NDT Solutions Ltd | St Helens | 2018 |
| Ndtek Access Ltd | Castle Douglas | 2025 |
| NE Marine and Offshore Services Ltd | Montrose | 2020 |
| NE Rigging Ltd | North Shields | 2024 |
| NE Verification Ltd | Carluke | 2014 |
| NEC Inspections Ltd | Peterhead | 2019 |
| Needham Chalks (HAM) Limited | Bishop'S Stortford | 1993 |
| Needham Geoscience Limited | Ilkley | 2007 |
| Nehemiah Construction Ministries UK Limited | Leicester | 2008 |
| Neil Adams Mechanical Services Limited | Swadlincote | 2009 |
| Neil Mullin & Sons Limited | | 1987 |
| Nelson Cummings Well Services Limited | Newark | 2018 |
| Nelson Inspection Ltd | Sheffield | 2020 |
| NEO Energy Asia (U.K) Limited | London | 2013 |
| NEO GEO Consulting Ltd | Falmouth | 2025 |
| NEO Next + Energy (GBA) Limited | London | 2023 |
| NEO Next + Energy Alpha Limited | London | 2003 |
| NEO Next + Energy Beta Limited | London | 2003 |
| NEO Next + Energy Delta Limited | London | 2017 |
| NEO Next + Energy LNS Limited | London | 1990 |
| NEO Next + Energy North Sea Limited | London | 1972 |
| NEO Next + Energy Offshore GB Limited | London | 1998 |
| NEO Next + Energy OIL Trading Limited | London | 1988 |
| NEO Next + Energy Resources UK Limited | London | 1964 |
| NEO Next + Energy Zeta Limited | London | 2018 |
| NEO Next+ Energy (Production) Limited | London | 2006 |
| NEO Next+ Energy (SNS) Limited | Aberdeen | 2005 |
| NEO Next+ Energy (Ukcs) Limited | London | 1991 |
| NEO Next+ Energy (ZEL) Limited | London | 2008 |
| NEO Next+ Energy (ZEX) Limited | London | 2006 |
| NEO Next+ Energy (ZNI) Limited | Belfast | 1995 |
| NEO Next+ Energy (ZPL) Limited | London | 2013 |
| NEO Next+ Energy Central North Sea Limited | London | 2006 |