| Mollex Lettings Ltd | Real estate | 2020 |
| Mollex Ltd | Construction | 2026 |
| Mollex Services Ltd | Administrative & support | 2020 |
| Moms Fabulous Foods Ltd | Extraterritorial | 2011 |
| Monicol Services Ltd | Households | 2025 |
| Moonrose Ltd | Hospitality | 2024 |
| Moorhouse Group Holdings Limited | Financial services | 2002 |
| Moorhouse Group Limited | Financial services | 1999 |
| Moorhouse Xbroker Limited | Financial services | 2003 |
| Moray Luke Limited | Wholesale & retail | 2020 |
| Morgan & Morgan Residential Property Limited | Real estate | 2025 |
| Morgan Fleet Care Ltd | Wholesale & retail | 2023 |
| Morgan Francis Limited | Construction | 2025 |
| Morgans Build & Design Ltd | Construction | 2025 |
| Moricon Ltd | Administrative & support | 2023 |
| Morris Rail Consultancy Ltd | Other services | 2022 |
| Moruzzi Haulage Limited | Transport & logistics | 2024 |
| Moses Properties SW Limited | Real estate | 2025 |
| Mosi Investments UK Limited | Real estate | 2024 |
| Motocross UK Ltd | Wholesale & retail | 2020 |
| Motormode Caerphilly Ltd | Wholesale & retail | 2025 |
| Mountain View Ranch Ltd | Arts & recreation | 2012 |
| Moving Away Ltd | Extraterritorial | 2012 |
| Mpasuk Ltd | Professional & scientific | 2020 |
| MPDT1 Ltd | Other services | 2018 |
| MPDT2 Ltd | Other services | 2016 |
| MPDT3 Ltd | Extraterritorial | 2015 |
| MPDT4 Ltd | Extraterritorial | 2018 |
| MPDT5 Ltd | Other services | 2015 |
| MR Chippy Caerphilly Limited | Hospitality | 2021 |
| MR Scuffs Ltd | Wholesale & retail | 2023 |
| MRA Foods Ltd | Hospitality | 2021 |
| MRJ Brothers Ltd | Real estate | 2025 |
| MRJ Recovery Ltd | Transport & logistics | 2026 |
| MRM Logistics Ltd | Transport & logistics | 2021 |
| MSB Air Conditioning Limited | Energy | 2023 |
| MSR Holdings Ltd | Real estate | 2023 |
| Multishield Group Limited | Manufacturing | 2025 |
| Muse Socials Ltd | Administrative & support | 2024 |
| Mushroom Health and Nutrition Ltd | Manufacturing | 2023 |
| My Choice Healthcare South Wales Limited | Financial services | 2020 |
| My Coed Fish Bar Ltd | Hospitality | 2024 |
| My Garment Factory Limited | Manufacturing | 2014 |
| My GIG Guide CIC | Information & communication | 2021 |
| My Hope Trading Limited | Wholesale & retail | 2024 |
| My Lettings (Merthyr) Ltd | Real estate | 2024 |
| My Lettings Limited | Real estate | 2012 |
| My Mortgage Advice Centre Ltd | Financial services | 2019 |
| My-Hub Ltd | Professional & scientific | 2019 |
| Myra Design Ltd | Manufacturing | 2020 |
| N and ST Property Ltd | Real estate | 2025 |
| N Prosser Building Maintenance Ltd | Construction | 2018 |
| Nailsbybrooke CYF | Other services | 2025 |
| Nataim UK Limited | Construction | 2003 |
| National Education Partnership CIC | Education | 2026 |
| National Roofing & Cladding Solutions Ltd | Construction | 2022 |
| Naturenurture.Education CIC | Agriculture & fishing | 2023 |
| NC Metal Recycling Ltd | Water & waste | 2013 |
| Nehir London Limited | Hospitality | 2018 |
| Nelson Fields Limited | Construction | 2016 |
| New AGE Investments Limited | Real estate | 2018 |
| New Caerphilly Fish Bar & Cafe Ltd | Hospitality | 2024 |
| New Horizons Youth Theatre Ltd | Arts & recreation | 2025 |
| New Little Village Ltd | Hospitality | 2026 |
| New Old Woolies Ltd | Wholesale & retail | 2026 |
| Newday Consulting Ltd | Professional & scientific | 2002 |
| Newlook Upholstery Limited | Manufacturing | 1999 |
| Newmodel Limited | Professional & scientific | 1998 |
| NGC Resolution Ltd | Information & communication | 2014 |
| Niche Fitness Ltd | Hospitality | 2019 |
| Niche Lane Limited | Wholesale & retail | 2015 |
| Nick Lazarou Hair Salon Ltd | Other services | 2026 |
| Nifty Code Ltd | Information & communication | 2020 |
| Nightingale Care Beds Limited | Extraterritorial | 1993 |
| Nightingale HQ Limited | Information & communication | 2018 |
| Nikki Miller Construction Services Ltd | Administrative & support | 2018 |
| Niro Contractors Ltd | Administrative & support | 2026 |
| NKW Contract Flooring Ltd | Construction | 2026 |
| NLO Properties Ltd | Real estate | 2023 |
| NM Rugby Academy Ltd | Education | 2024 |
| NO Child Left Behind Sports Coaching & Development Ltd | Arts & recreation | 2019 |
| NO Ghost Limited | Information & communication | 2015 |
| Northants Contemporary Jazz Limited | Arts & recreation | 2008 |
| Norton Education Services Ltd | Education | 2024 |
| NOT Broken Ltd | Wholesale & retail | 2015 |
| Notetop Office Solutions Limited | Wholesale & retail | 1980 |
| Novora Asset Finance Ltd | Financial services | 2025 |
| Novu Motor Sales Ltd | Wholesale & retail | 2025 |
| NPL Medical Services Limited | Manufacturing | 2008 |
| NRJ Property Limited | Real estate | 2018 |
| NU Rose Tattoos Limited | Other services | 2013 |
| Nula Properties Limited | Real estate | 2007 |
| Nulla Carbo Fabrica Ltd | Professional & scientific | 2023 |
| Nurish Foods Limited | Extraterritorial | 2002 |
| Nurture Play Cafe Limited | Hospitality | 2025 |
| NXT Nutrition Ltd | Manufacturing | 2025 |
| O'Brien Construction (South Wales) Limited | Construction | 2015 |
| O'Leary Technologies Ltd | Manufacturing | 2026 |
| Oak Property Development (South Wales) Ltd | Real estate | 2022 |
| Oak Safety Solutions Limited | Professional & scientific | 2023 |