| Middleton Cheney Pre-School Limited | Education | 2012 |
| Middleton House Residents Limited | Households | 2019 |
| Middleton Jeffers Recruitment Limited | Administrative & support | 2001 |
| Middleton Madras Ltd | Hospitality | 2023 |
| Middleton Trade Ltd | Wholesale & retail | 2024 |
| Midland Trade Frames Limited | Construction | 2007 |
| Midlands Mediation Office Ltd | Professional & scientific | 2012 |
| MIG Engineering Solutions Ltd | Professional & scientific | 2018 |
| Migrationwatchuk | Information & communication | 2002 |
| Mike Champion Engineering Ltd | Manufacturing | 2013 |
| Mikel-Uk Ltd | Wholesale & retail | 2019 |
| Mill Field Island Ltd | Agriculture & fishing | 2023 |
| Mill Valley Properties Limited | Construction | 2024 |
| Millben Limited | Administrative & support | 2004 |
| Millen Inns Limited | Hospitality | 2021 |
| Millenium Foods Limited | Hospitality | 2024 |
| Miller Heating & Plumbing Contractors Ltd | Construction | 2022 |
| Milmil Studio Ltd | Wholesale & retail | 2023 |
| Milosz Limited | Wholesale & retail | 2024 |
| Mimi Hair Lounge Limited | Other services | 2023 |
| Mind Education School Academy Limited | Education | 2022 |
| Mind Education School Limited | Education | 2015 |
| Mindgrid AI Ltd | Information & communication | 2025 |
| Minkseal Limited | Real estate | 1993 |
| Minosa Ltd | Health & social care | 2026 |
| Minotaur Limited | Real estate | 2013 |
| Minotaur Prime Investments Limited | Real estate | 2014 |
| Mintondale Developments Ltd | Real estate | 2012 |
| Miranda Markham Events Limited | Administrative & support | 2022 |
| Mirror Gilding Ltd | Professional & scientific | 2022 |
| Mirror Quark Limited | Professional & scientific | 2017 |
| Mirrorsphere Group Ltd. | Financial services | 2019 |
| Mirrorsphere Ltd. | Information & communication | 2007 |
| Miskin Holdings Limited | Real estate | 2021 |
| Miss Briosa Ltd | Transport & logistics | 2023 |
| Mithcet Ltd | Professional & scientific | 2012 |
| Mitusrl Ltd | Transport & logistics | 2025 |
| MIY Build Ltd | Manufacturing | 2025 |
| MJ TEC Ltd | Wholesale & retail | 2010 |
| MJB Leisure Sales & Solutions Ltd | Wholesale & retail | 2026 |
| Mjct Limited | Professional & scientific | 2003 |
| MJE Clothing Limited | Wholesale & retail | 2019 |
| MJG Utilities Ltd | Construction | 2026 |
| Mjhrp Limited | Real estate | 2020 |
| MK Back and Spine Limited | Health & social care | 2018 |
| MKL Creations Limited | Wholesale & retail | 2020 |
| MKS Transport Ltd | Construction | 2023 |
| ML Ventures Limited | Hospitality | 2007 |
| Mlipski Ltd | Transport & logistics | 2018 |
| MLR Funding Solutions Ltd | Financial services | 2015 |
| MLV Holdco Limited | Financial services | 2022 |
| MMD Stores Limited | Wholesale & retail | 2022 |
| Mmery Nails Banbury Ltd | Other services | 2023 |
| Mmjf Ltd | Real estate | 2025 |
| Mmmz Limited | Professional & scientific | 2013 |
| MMS Care Services Limited | Health & social care | 2025 |
| MNR IT Testing Services Ltd | Professional & scientific | 2022 |
| Mobile Alloy Solutions Ltd | Wholesale & retail | 2025 |
| Mobile Tyres Ondemand Ltd | Wholesale & retail | 2024 |
| Mobio Distribution Ltd | Wholesale & retail | 2019 |
| Mobio Holdings Limited | Financial services | 2023 |
| Mobley Limited | Construction | 1995 |
| Moderation Associates Ltd | Professional & scientific | 2022 |
| Modex Exhibitions Limited | Administrative & support | 2003 |
| Modex Holdings Limited | Financial services | 2020 |
| Modex Show Ready Ltd | Administrative & support | 2022 |
| Molded Candy Ltd | Professional & scientific | 2020 |
| Monkeywood Limited | Manufacturing | 2023 |
| Montague Group Services Limited | Construction | 2018 |
| Montivor Ltd | Wholesale & retail | 2026 |
| Montpelier (Chatham) Limited | Real estate | 2022 |
| Montpelier Designs Limited | Construction | 2024 |
| Montpelier Estates Limited | Construction | 1997 |
| Montpelier Integrated Care Limited | Construction | 2021 |
| Montralis Group Ltd | Information & communication | 2025 |
| MOO Bells Ltd | Hospitality | 2026 |
| MOO Meadows Limited | Households | 2021 |
| Moon MED Comms Ltd | Professional & scientific | 2025 |
| Moonraker Holdings Ltd | Financial services | 2022 |
| Moorland House Management Company Limited | Households | 1991 |
| Moose Revive Ltd | Wholesale & retail | 2024 |
| Moran Gynaecology Services Limited | Health & social care | 2010 |
| Mosaic Performance Pools Ltd | Professional & scientific | 2010 |
| Mosaic Swimming Pools and Spas Limited | Construction | 2003 |
| Motec (Europe) Limited | Wholesale & retail | 1996 |
| Motikray Limited | Information & communication | 2021 |
| Motion Service & Repairs Ltd | Wholesale & retail | 2020 |
| Motorhomes 4 Motorsport Limited | Administrative & support | 2008 |
| Moviemate Limited | Administrative & support | 2025 |
| Mozza Limited | Information & communication | 2002 |
| MPG Logistics Ltd | Transport & logistics | 2019 |
| MR Abundance Ltd | Professional & scientific | 2018 |
| MR Frosty & Daughters Limited | Hospitality | 2021 |
| MR Mooping! Limited | Administrative & support | 2023 |
| MR Rice Banbury Limited | Hospitality | 2021 |
| MR Singh and Kaur Ltd | Wholesale & retail | 2020 |
| MR Souvlaki Banbury Limited | Hospitality | 2024 |
| MR. Souvlaki Limited | Hospitality | 2020 |
| MRC Tuning Limited | Wholesale & retail | 2008 |
| MRN Engineering Limited | Manufacturing | 2014 |