| Monmouthshire Events Ltd | Administrative & support | 2024 |
| Monster Junk Wrexham Ltd | Water & waste | 2024 |
| Monty's Penguin Limited | Information & communication | 2023 |
| Morlove Ltd | Information & communication | 2017 |
| Morris' MOO Shoes Ltd | Agriculture & fishing | 2017 |
| Mosaic Business and Technology Consulting Ltd | Information & communication | 2016 |
| Motor FIX Chepstow Limited | Wholesale & retail | 2025 |
| Motor Services (Bath) Ltd | Professional & scientific | 1981 |
| Mounton Brook Lodge Ltd | Professional & scientific | 2015 |
| MOVE2CLOUD Advisory Services Limited | Professional & scientific | 2020 |
| MR T. Butt T/A the Wood Bandits V the IT Nerds Ltd | Information & communication | 2026 |
| MR T.Butt & the Crown Jewel Bespoke IT and Renaovation Services Limited | Information & communication | 2026 |
| MST Properties Ltd | Construction | 2009 |
| Muca Motors Ltd | Wholesale & retail | 2017 |
| Muscle Buddy Ltd | Wholesale & retail | 2025 |
| MVM Entertainment Limited | Wholesale & retail | 2005 |
| MVR Consulting Ltd | Information & communication | 2012 |
| Mynyddbach Developments Ltd | Construction | 2018 |
| Mypets Limited | Wholesale & retail | 2015 |
| Myseoul Nails & Beauty Lounge Ltd | Other services | 2025 |
| Mythonic Consulting Limited | Information & communication | 2023 |
| Mythonic Trading Limited | Wholesale & retail | 2021 |
| N.D.A.C. Limited | Professional & scientific | 2005 |
| Nammu Tech Ltd | Administrative & support | 2017 |
| Natures Habitat Limited | Wholesale & retail | 2016 |
| NCJ Group Limited | Financial services | 2002 |
| ND Contracts (South West) Limited | Construction | 2026 |
| Negative Space Studios Limited | Information & communication | 2020 |
| Neil Gallagher Operational Excellence Ltd | Professional & scientific | 2018 |
| Netherton Tech Park Ltd | Construction | 2020 |
| New Hall Property Investments Limited | Construction | 2020 |
| Newman and Eastwood Limited | Professional & scientific | 2013 |
| Newport H Limited | Manufacturing | 2001 |
| Newportg Limited | Financial services | 2017 |
| Newton Software Limited | Information & communication | 1990 |
| Nexus Consulting Group Limited | Professional & scientific | 2022 |
| NG Legal Services Ltd | Professional & scientific | 2024 |
| Nhpil EOT Management Limited | Construction | 2023 |
| Nightingale Automation Limited | Construction | 2022 |
| Nightingale Renewable Limited | Construction | 2022 |
| Nimbus Solar Ltd | Construction | 2022 |
| Node Imaging Ltd | Information & communication | 2026 |
| Nomadgear Ltd | Administrative & support | 2026 |
| Nomadic SKI Holidays Limited | Hospitality | 2003 |
| Norton Plantaria Limited | Wholesale & retail | 2022 |
| Notanant Limited | Information & communication | 2006 |
| Noufy's Ltd | Hospitality | 2024 |
| Nova Luxe Ltd | Wholesale & retail | 2023 |
| NSD Composite Floor Decks Ltd | Construction | 2009 |
| Oak EYE Limited | Information & communication | 2024 |
| Oakey Dokey Ltd | Construction | 2018 |
| Oaklands Technical Services Limited | Information & communication | 2011 |
| OCT Homemaker Limited | Construction | 2026 |
| OCW Engineering Services Limited | Professional & scientific | 2010 |
| OG Publishing Ltd | Information & communication | 2018 |
| OH Hello Box Ltd | Wholesale & retail | 2025 |
| OMB Business Services Ltd | Professional & scientific | 2020 |
| ON Cans Ltd | Information & communication | 2014 |
| ON Point Brew Company Limited | Manufacturing | 2009 |
| ON Screen Productions Ltd | Administrative & support | 1993 |
| One Call Caterer Limited | Hospitality | 2006 |
| One Hand Lift Limited | Professional & scientific | 2017 |
| One to Four Limited | Professional & scientific | 2000 |
| One Tribe TV Limited | Information & communication | 2011 |
| One World Events Limited | Administrative & support | 2017 |
| One World Property Group Limited | Real estate | 2017 |
| One World Venture Group Ltd | Construction | 2020 |
| Only Booz Limited | Hospitality | 2025 |
| Only Foodz and Sauces Limited | Hospitality | 2025 |
| Only Foodz Socials Limited | Professional & scientific | 2025 |
| Only Treatz Ltd | Hospitality | 2025 |
| Orchard Mortgages Ltd | Financial services | 2016 |
| Orchascan Limited | Administrative & support | 2021 |
| Original Pictures Distribution Limited | Information & communication | 2011 |
| Ormrod Property Ltd | Real estate | 2018 |
| Osborn-Unipol (UK) Limited | Manufacturing | 1941 |
| Osnlolo Limited | Financial services | 2024 |
| OSP Exhibitions Limited | Administrative & support | 2024 |
| OSP Healthcare Limited | Information & communication | 2013 |
| OSP NO 3 Limited | Professional & scientific | 2017 |
| OSP NO2 Limited | Administrative & support | 2015 |
| Outpost Facilities Limited | Information & communication | 1999 |
| Overbilt Designs Limited | Professional & scientific | 2024 |
| Owens Ground Maintenance Limited | Administrative & support | 2007 |
| Ozturk 2 Recoveries Limited | Professional & scientific | 2022 |
| O’Mullens Civil Engineering Limited | Construction | 2025 |
| P & M Property Development Limited | Real estate | 2000 |
| P & S Property Development 2021 Limited | Real estate | 2021 |
| P M R Products Limited | Manufacturing | 1994 |
| Padel by Gabriela Ltd | Professional & scientific | 2012 |
| Padel Centres Limited | Arts & recreation | 2020 |
| Panda and the Portrait Productions Ltd | Information & communication | 2026 |
| Panda Oriental Kitchen Ltd | Hospitality | 2025 |
| Parry Business Services Limited | Professional & scientific | 2003 |
| Parsonage Productions Limited | Information & communication | 2021 |
| Parva Spices Limited | Manufacturing | 2016 |
| Passif Prints Ltd | Wholesale & retail | 2026 |
| Patience Staff Supply Limited | Hospitality | 2022 |
| Payne Bros Holdings (UK) Ltd. | Wholesale & retail | 1999 |
| Payne Bros Ltd | Extraterritorial | 2017 |