| Miah's (Whickham) Limited | Administrative & support | 2024 |
| Miahdrive Limited | Wholesale & retail | 2025 |
| Michael Anderson Financial Services Ltd | Financial services | 2013 |
| Michael French Draughting Services Limited | Professional & scientific | 2008 |
| Michael Henderson & Co Limited | Professional & scientific | 2011 |
| Michael Hepworth Plumbing and Heating Limited | Construction | 2017 |
| Michael Mulhern Football Consultancy Ltd | Arts & recreation | 2026 |
| Michael Offord Optometrist Limited | Wholesale & retail | 2016 |
| Michael Sehgal & Sons Limited | Wholesale & retail | 1990 |
| Michael Sehgal Properties (North East) Limited | Construction | 2003 |
| Michael Sehgal Property Company Limited | Real estate | 1998 |
| Michael Super Store Ltd | Administrative & support | 2010 |
| Michael Tate Machinery Limited | Wholesale & retail | 2013 |
| Michell Bearings Limited | Manufacturing | 2015 |
| Michigan Industries Limited | Wholesale & retail | 1987 |
| Michigan Investments Limited | Real estate | 2012 |
| Michigan Limited | Extraterritorial | 2016 |
| Mickeycat Select Ltd | Wholesale & retail | 2025 |
| Micklewood Park Residents Management Company Limited | Real estate | 2012 |
| Micro Film Ltd | Information & communication | 2014 |
| Micro PUB North 1 Ltd | Hospitality | 2019 |
| Microdynamics Ltd | Information & communication | 2026 |
| Micropub Jesmond Limited | Hospitality | 2023 |
| Microsurgery North East Ltd | Health & social care | 2026 |
| Microtima Properties Limited | Real estate | 2003 |
| Microvention UK Limited | Health & social care | 2002 |
| MID East Newcastle Ltd | Hospitality | 2026 |
| MID Essex Hospital Project Limited | Other services | 2005 |
| Midas Digital Hosting Ltd | Information & communication | 2021 |
| Midas Digital NE Ltd | Professional & scientific | 2020 |
| Midas Holdings UK Ltd | Financial services | 2025 |
| Midas Physiotherapy Newcastle Ltd | Health & social care | 2018 |
| Midas Upholstery Limited | Water & waste | 1973 |
| Middle East 1 Limited | Wholesale & retail | 2021 |
| Middle East 2 Limited | Hospitality | 2021 |
| Middleone Limited | Administrative & support | 2002 |
| Middlesbrough Empire 2008 Limited | Hospitality | 2008 |
| Middleton Enterprises (2) Limited | Other services | 2020 |
| Middleton Enterprises (Holdings) Limited | Professional & scientific | 2013 |
| Middleton Enterprises Ltd | Other services | 1992 |
| Middlewood Management Ltd | Households | 2021 |
| Middlewood Park Maintenance (NO. 1) Limited | Real estate | 1993 |
| Middlewood Park Maintenance (NO. 2) Limited | Real estate | 1994 |
| Mide-First Consult Ltd | Health & social care | 2022 |
| Mides Square Ltd | Professional & scientific | 2025 |
| Midihouse Domestics Limited | Other services | 1973 |
| Midland Road Finance Limited | Financial services | 2014 |
| Midlands Powergrid Limited | Extraterritorial | 2011 |
| Midsommar Bakery Ltd | Hospitality | 2025 |
| Midwood Generator Services Ltd | Manufacturing | 2021 |
| Mielikki GIN Ltd | Manufacturing | 2019 |
| Mightty Ltd | Administrative & support | 2024 |
| Mighty Bite Newcastle Ltd | Hospitality | 2023 |
| Mighty Developers Ltd | Construction | 2024 |
| Mihai’S Cleaning Ltd | Administrative & support | 2025 |
| Mike Clark Book-Keeping Services Limited | Professional & scientific | 2002 |
| Mike Giblin Illustration Limited | Arts & recreation | 2011 |
| Mike Leung Holdings Limited | Information & communication | 2023 |
| Mike Lynch Advertising Limited | Professional & scientific | 2003 |
| Mike Procter Consulting Ltd | Professional & scientific | 2011 |
| Mikecrichards Limited | Health & social care | 2019 |
| Milan Express NE Ltd | Wholesale & retail | 2023 |
| Milburn Construction Limited | Construction | 2023 |
| Milburn Group Limited | Financial services | 2025 |
| Milburn Plant Limited | Administrative & support | 2022 |
| Mile END (Management) Limited | Real estate | 2007 |
| Miles Makers Ltd | Transport & logistics | 2025 |
| Mill Court Whitburn (Management) Limited | Households | 1976 |
| Mill House PUB Company Ltd | Hospitality | 2026 |
| Mill Lane Halal Butcher Limited | Wholesale & retail | 2019 |
| Mill Race Court Management Limited | Real estate | 2004 |
| Millenium MOT Centre Limited | Wholesale & retail | 2000 |
| Millennial Management Ltd | Professional & scientific | 2018 |
| Millennium Balloons Limited | Wholesale & retail | 2015 |
| Millennium Ices Ltd | Hospitality | 2025 |
| Millennium Industrial Cleaning Services Limited | Administrative & support | 2014 |
| Millennium Refrigeration Limited | Energy | 2009 |
| Miller Partnership Architects Limited | Professional & scientific | 2012 |
| Millers Dene Day Care CIC | Education | 2010 |
| Millfield Composites Group Limited | Professional & scientific | 2015 |
| Millfield Composites Limited | Manufacturing | 2009 |
| Millfield Construction Solutions Limited | Manufacturing | 2010 |
| Millfield Enterprises (Manufacturing) Limited | Manufacturing | 1986 |
| Millfield Enterprises Group Limited | Professional & scientific | 2015 |
| Millfield Group Ltd | Financial services | 2026 |
| Millfield GRP North West Limited | Construction | 2015 |
| Millfield GRP Products Limited | Manufacturing | 1996 |
| Millfield Patterns Limited | Manufacturing | 2002 |
| Millfield Properties Holdings Limited | Financial services | 2016 |
| Millfield Terminations Limited | Professional & scientific | 2018 |
| Milligans Durham Limited | Wholesale & retail | 2020 |
| Milligans Kenton Limited | Wholesale & retail | 2020 |
| Milligans Middlesbrough Limited | Wholesale & retail | 2020 |
| Milligans Monkseaton Limited | Wholesale & retail | 2020 |
| Milligans Newcastle Limited | Wholesale & retail | 2020 |
| Milligans Whickham Limited | Wholesale & retail | 2020 |
| Mills & Co. Solicitors Ltd | Professional & scientific | 2015 |
| Millys Munchies Limited | Wholesale & retail | 2023 |
| Milon Enterprise & MAS Bazar Ltd | Wholesale & retail | 2015 |
| Miltin Crafts Ltd | Wholesale & retail | 2021 |