| LRG Instrumentation Ltd | Professional & scientific | 2023 |
| Lscraftonaccessservices Limited | Manufacturing | 2026 |
| LSM Associates Ltd | Professional & scientific | 2022 |
| LTA Engineering Ltd | Professional & scientific | 2019 |
| Luckrise Limited | Real estate | 2025 |
| LUCKY91 Limited | Hospitality | 2025 |
| Lune Club Ltd | Wholesale & retail | 2024 |
| M & K Properties Teesside Ltd | Real estate | 2021 |
| M & L Groundworks Limited | Construction | 2014 |
| M & S Mckillop Garden Services Ltd | Administrative & support | 2023 |
| M . R . Crane Services Limited | Other services | 2017 |
| M Booth Engineering Limited | Construction | 2024 |
| M Buckworth and SON Property Ltd | Real estate | 2018 |
| M H Roberts Limited | Wholesale & retail | 2011 |
| M J & a Electrical Services Limited | Other services | 2011 |
| M Puckrin Electrical Services Limited | Construction | 2014 |
| M W Holiday Homes Limited | Hospitality | 2021 |
| M&F Fabrication Ltd | Manufacturing | 2024 |
| M&O Homes Ltd | Real estate | 2021 |
| M.J. Scaife Limited | Professional & scientific | 1995 |
| M.K.G Cleaning Service Ltd | Manufacturing | 2026 |
| MAC Engineering Solutions Limited | Professional & scientific | 2007 |
| Made Property Developments Ltd | Real estate | 2021 |
| Magic Properties Group LLP | | 2017 |
| Magic Properties Limited | Real estate | 2006 |
| Magna Pecunia Ltd | Wholesale & retail | 2025 |
| Mahadev Solutions Ltd | Wholesale & retail | 2026 |
| Majuba Limited | Hospitality | 2018 |
| Malvern Installation Ltd | Manufacturing | 2016 |
| Managh House Limited | Real estate | 2020 |
| Manhattan INK Chesham Ltd | Arts & recreation | 2019 |
| Manhattan INK Faringdon Ltd | Arts & recreation | 2018 |
| Manhattan INK Ltd | Arts & recreation | 2016 |
| Manhattan INK Rushden Ltd | Arts & recreation | 2017 |
| Mansfield Installations Ltd | Construction | 2026 |
| Margaret's House Limited | Hospitality | 2024 |
| Marina Bites Ltd | Hospitality | 2025 |
| Marske Auto Tech Limited | Wholesale & retail | 2006 |
| Marske Centre Limited(The) | Arts & recreation | 1983 |
| Marske Fast Food Ltd | Hospitality | 2025 |
| Marske Food Ltd | Hospitality | 2025 |
| Marske Funeral Services Ltd | Other services | 2015 |
| Marske Hand Carwash Limited | Administrative & support | 2024 |
| Marske Instrument & Controls Limited | Other services | 2014 |
| Marton Windows Limited | Construction | 2001 |
| Mascot Madness Limited | Administrative & support | 2025 |
| Maxx Property Ltd | Real estate | 2023 |
| Mayfair & Regent LLP | | 2021 |
| MCD Systems Ltd | Information & communication | 2017 |
| Mcgeady's Instrument Services Ltd | Professional & scientific | 2022 |
| Mcgeady`S Limited | Construction | 2007 |
| MCL Safety Management Limited | Professional & scientific | 2015 |
| Mcnaught & Barker Properties Ltd | Real estate | 2021 |
| Mcquade Property Developments Ltd | Real estate | 2019 |
| Mcquillan Electrical Services Ltd | Construction | 2025 |
| Mcquillan Projects Ltd | Construction | 2026 |
| MD Davies Ltd | Real estate | 2025 |
| MD Foods NE Ltd | Hospitality | 2025 |
| Mechman Ltd | Professional & scientific | 2026 |
| Mecl Consulting Ltd | Information & communication | 2016 |
| Media Installations Ltd | Construction | 2018 |
| Media Solutions (North East) Ltd | Professional & scientific | 2003 |
| Medics UK (North East) Limited | Health & social care | 2016 |
| Meef Investments LLP | | 2022 |
| Meehu Ltd | Wholesale & retail | 2014 |
| Meraki Hairdressing Ltd | Other services | 2025 |
| Merc Specialist Garage Ltd | Wholesale & retail | 2026 |
| MGP PUB Company Ltd | Hospitality | 2025 |
| Michael Revell Logistics Ltd | Transport & logistics | 2025 |
| Michael Sreenan Ltd | Information & communication | 2021 |
| Micropore Technologies Ltd | Manufacturing | 2003 |
| Middlestone Housing Ltd | Real estate | 2025 |
| Mighty Redcar Limited | Real estate | 2019 |
| Mike & SON Property Ltd | Households | 2025 |
| Minder Healthcare Ltd | Information & communication | 2021 |
| Minder Property Ltd | Real estate | 2022 |
| Minotaur Investments Ltd | Households | 2026 |
| Mintlab Communications Limited | Professional & scientific | 2024 |
| Miss SKJ Property Ltd | Real estate | 2019 |
| MJ Trade Ltd | Construction | 2026 |
| MJC Homes Ltd | Real estate | 2018 |
| MJG Lifting Consultancy Ltd | Manufacturing | 2023 |
| MJP Consultants Ltd | Professional & scientific | 2018 |
| Mjpsp Property Ltd | Real estate | 2025 |
| ML Services & Engineering Ltd | Professional & scientific | 2023 |
| ML Stuart Properties Ltd | Real estate | 2024 |
| MMD ENG Limited | Construction | 2016 |
| Mo's Palace Ltd | Wholesale & retail | 2009 |
| MOJ Homes Ltd | Real estate | 2024 |
| Monument Financial Services Limited | Financial services | 2008 |
| Motorcash Limited | Professional & scientific | 2010 |
| MP Custom Autos Ltd | Wholesale & retail | 2024 |
| MP Heavy Lift Specialist Ltd | Manufacturing | 2026 |
| MP2ENGINEERING Ltd | Construction | 2024 |
| MPH Associates Limited | Real estate | 2004 |
| MPS E&I Services Limited | Energy | 2014 |
| MR Bentley's EST. 2019 Ltd | Hospitality | 2019 |
| MR Brickworks NE Ltd | Construction | 2019 |
| MR Shawarma NE Ltd | Hospitality | 2025 |
| Mrnj Properties LLP | | 2020 |