| Mervyn Greatrix Commercial Vehicle Repairs Ltd | Wholesale & retail | 2025 |
| Messrs Richardson & Dickinson Properties Ltd | Real estate | 2016 |
| Metframe Ltd | Construction | 2015 |
| Metsa Board UK Limited | Wholesale & retail | 1951 |
| Metsa Wood UK Limited | Manufacturing | 1995 |
| Mfbh Ltd | Information & communication | 2025 |
| Mfes Services Limited | Professional & scientific | 2025 |
| MH Think Limited | Information & communication | 2012 |
| MHG Management Services Ltd | Construction | 2014 |
| Mhomes for Life Ltd | Real estate | 2025 |
| Mias Motors Ltd | Wholesale & retail | 2019 |
| MIC POL Trans Ltd | Transport & logistics | 2016 |
| Michelle's Mortgage Solutions Ltd | Financial services | 2019 |
| Mick D Solutions Limited | Administrative & support | 2013 |
| Mick Young Services Ltd | Transport & logistics | 2024 |
| Midgate Farms Limited | Agriculture & fishing | 2005 |
| Midgate Properties Limited | Real estate | 2003 |
| Midland Business Limited | Health & social care | 2022 |
| Midnight OWL Studios Ltd | Manufacturing | 2016 |
| Mihai Trans (Eastern) Ltd | Transport & logistics | 2015 |
| Mikea Ltd | Transport & logistics | 2018 |
| Milday Properties Limited | Real estate | 2019 |
| Mill Farm Leisure Ltd | Hospitality | 2015 |
| Mill Tyres (Boston) Limited | Extraterritorial | 2016 |
| Miller Greetings Ltd | Wholesale & retail | 2012 |
| Millers View Limited | Other services | 2008 |
| Million Rides Limited | Transport & logistics | 2019 |
| Millpride Limited | Hospitality | 2011 |
| Milog Limited | Transport & logistics | 2025 |
| Minda Transport Ltd | Transport & logistics | 2022 |
| Mindy Trans Ltd | Transport & logistics | 2018 |
| Minerva Consulting Services Ltd | Professional & scientific | 2024 |
| Minhas & Co Ltd | Health & social care | 2014 |
| Misiuna Ltd | Transport & logistics | 2019 |
| Mitya Properties Ltd | Real estate | 2026 |
| Mixmatch UK Traders Ltd | Wholesale & retail | 2022 |
| MJ Accountancy Services (Boston) Limited | Professional & scientific | 2011 |
| MJS Engineering (Boston) Limited | Construction | 2011 |
| MK76 Services Ltd | Construction | 2022 |
| ML Wells Properties Ltd | Real estate | 2023 |
| MLH Media and Marketing Ltd | Professional & scientific | 2026 |
| MM Williams Properties Limited | Real estate | 2026 |
| Mmindo Ltd | Transport & logistics | 2024 |
| MMS Driving Ltd | Transport & logistics | 2018 |
| Mobifix Town Limited | Wholesale & retail | 2025 |
| Mobile Car Valeting (Boston) Limited | Wholesale & retail | 2018 |
| Mobile Mechanical Servicing Ltd | Wholesale & retail | 2024 |
| Mobile Zone Boston Ltd | Wholesale & retail | 2024 |
| Modris Trans Ltd | Transport & logistics | 2026 |
| Moeez Palace Ltd | Hospitality | 2025 |
| MONIAV8OSA Transport Ltd | Transport & logistics | 2024 |
| Monkey and I Ltd | Hospitality | 2021 |
| MOO 25 Ltd | Professional & scientific | 2025 |
| Moore Drivers Limited | Transport & logistics | 2010 |
| Moores Property Management Ltd | Real estate | 2025 |
| Mopy Trans Ltd | Transport & logistics | 2016 |
| Moralee and Mather Ltd | Real estate | 2021 |
| Morley Brown Howden Ltd | Professional & scientific | 2018 |
| Mortgages for YOU Ltd | Financial services | 2018 |
| MOS Pizza Perfection Boston Ltd | Hospitality | 2024 |
| Moskito Ltd | Administrative & support | 2014 |
| MOSSIM42 Ltd | Wholesale & retail | 2025 |
| Motkur Limited | Health & social care | 2018 |
| Moto Jasko Ltd | Transport & logistics | 2018 |
| Motondo Ltd | Real estate | 2017 |
| Motor Trade Consultations Ltd. | Wholesale & retail | 2023 |
| Motryx RW Limited | Wholesale & retail | 2025 |
| Moulton Limited | Financial services | 2017 |
| MOX Transport Limited | Transport & logistics | 2025 |
| MPC Thermal Limited | Construction | 2014 |
| Mpmt Ltd | Transport & logistics | 2017 |
| MR Mars Limited | Transport & logistics | 2019 |
| MR Motor INT Limited | Wholesale & retail | 2023 |
| MS Groundworks (Lincoln) Limited | Construction | 2019 |
| MS Jarex Ltd | Transport & logistics | 2018 |
| MS Recovery Ltd | Wholesale & retail | 2024 |
| MSG Trading Ltd | Wholesale & retail | 2020 |
| MTL Technology Solutions Ltd | Information & communication | 2015 |
| MTM Creations Ltd | Manufacturing | 2019 |
| Muiz Ltd | Wholesale & retail | 2025 |
| Multi Plumb Ltd | Construction | 2015 |
| Mummy & US Ltd | Wholesale & retail | 2024 |
| Munchonthemoveglobal Ltd | Hospitality | 2025 |
| Munks Agricultural Contractors Limited | Agriculture & fishing | 2021 |
| Mura Building Ltd | Manufacturing | 2018 |
| Murlec Holdings Limited | Financial services | 2024 |
| Murlec Limited | Construction | 2006 |
| Murrell Property Ltd | Real estate | 2023 |
| Musyu Fresh Fruit & VEG Ltd | Wholesale & retail | 2024 |
| MVS Traders Ltd | Wholesale & retail | 2025 |
| Mwko Ltd | Transport & logistics | 2023 |
| MXV Ltd | Wholesale & retail | 2022 |
| My Ideal Orange Limited | Health & social care | 2017 |
| Mystic Soul Collectables Limited | Wholesale & retail | 2020 |
| MZS Care Ltd | Health & social care | 2022 |
| N Mortlock Haulage Ltd | Transport & logistics | 2014 |
| N Omar Barbers Ltd | Other services | 2025 |
| N&N's Consulting Ltd | Health & social care | 2022 |
| N&S Cleaning Solutions Ltd | Administrative & support | 2018 |
| Naan Walla Grill & Pizza Limited | Hospitality | 2025 |