| Meeron Limited | Arts & recreation | 1998 |
| Meetang Limited | Hospitality | 2017 |
| MEG Catering Limited | Hospitality | 2025 |
| Megashine Window Cleaning Ltd | Administrative & support | 2023 |
| Meggephia Limited | Administrative & support | 2012 |
| Mehbi Ltd | Professional & scientific | 2023 |
| Mehreen Dine (Bourne) Ltd | Hospitality | 2013 |
| Melbourne Mews (Apartments) Management Company Limited | Households | 2021 |
| Melbourne Mews (Wheathampstead) Management Company Limited | Households | 2021 |
| Melecorp Ltd | Manufacturing | 2016 |
| Melodic Minor Limited | Information & communication | 2026 |
| Melroxx Limited | Health & social care | 2023 |
| Melton Lettings Limited | Real estate | 2015 |
| Menaoye Group Limited | Health & social care | 2018 |
| Mental Health and ME CIC | Health & social care | 2025 |
| MEP Management and Consulting Ltd | Professional & scientific | 2023 |
| Merakiulus Limited | Other services | 2018 |
| Merc Specialist Ltd | Wholesale & retail | 2025 |
| Merchants Quarter (Stevenage) Management Company Limited | Households | 2010 |
| Mercia Fleet FIX Limited | Wholesale & retail | 2026 |
| Meridian Horizon Limited | Wholesale & retail | 2025 |
| Merryland Cuisine Ltd | Hospitality | 2019 |
| Merton Avenue Limited | Information & communication | 2017 |
| Mesic Ltd | Information & communication | 2018 |
| Mesic Tofan Group Limited | Real estate | 2025 |
| Mesoura Limited | Information & communication | 2024 |
| MET Recruitment (London) Ltd | Administrative & support | 2013 |
| Meta Auctions Limited | Other services | 2022 |
| Metro Shutters Limited | Manufacturing | 2015 |
| MEW Associates Ltd | Professional & scientific | 2007 |
| Meyra Holdings Limited | Real estate | 2020 |
| Mfor Transformation Limited | Information & communication | 2023 |
| MG Construct Ltd | Construction | 2017 |
| MG Hair Design Ltd | Other services | 2018 |
| Mg-Fm Services Limited | Administrative & support | 2021 |
| MGL Transport Ltd | Transport & logistics | 2026 |
| MGM Hotels Limited | Hospitality | 2004 |
| MGM OBI Limited | Health & social care | 2022 |
| Mgreenscenery Ltd | Construction | 2025 |
| MH Global Property Services Ltd | Real estate | 2023 |
| MH UK Properties Limited | Real estate | 2025 |
| MHB Eats Ltd | Hospitality | 2024 |
| Mhmblue Limited | Information & communication | 2025 |
| MHS Global Holdings Ltd | Administrative & support | 2026 |
| MI Construction Trading Ltd | Construction | 2014 |
| MI Design Associates Ltd | Wholesale & retail | 2006 |
| MI Drylining Systems Ltd | Construction | 2025 |
| Mi&Bg Construction Ltd | Construction | 2025 |
| Miah B Limited | Wholesale & retail | 2019 |
| MIC Healthcare Solutions Limited | Health & social care | 2018 |
| Michael Tuohy Limited | Administrative & support | 2000 |
| Michb Ltd | Health & social care | 2023 |
| Michella Retail Ltd | Wholesale & retail | 2016 |
| Midas Exchange Limited | Extraterritorial | 2005 |
| Midas Projects Limited | Administrative & support | 2000 |
| Middle Kingdom Imports Ltd | Wholesale & retail | 2023 |
| Middlemarch Residents Association Limited | Real estate | 2006 |
| Midesquare Ltd | Professional & scientific | 2019 |
| Midtown Motors Ltd | Wholesale & retail | 2019 |
| Mihikavi Ltd | Health & social care | 2020 |
| MIK Motors Ltd | Wholesale & retail | 2026 |
| Miko Properties Ltd | Real estate | 2026 |
| Mikydutz Inc Ltd | Wholesale & retail | 2019 |
| Mila Solutions Limited | Other services | 2014 |
| Milan Mart Ltd | Information & communication | 2024 |
| Mildean Ltd | Construction | 2023 |
| Mill Green (Hatfield) Management Company Limited | Households | 2022 |
| Mill Park Limited | Hospitality | 2015 |
| Mill Park Trading Company Limited | Hospitality | 2023 |
| Millie Mcbride Dressage Ltd | Arts & recreation | 2021 |
| Mills Fencing Ltd | Construction | 2006 |
| Mills Retail Group Ltd | Wholesale & retail | 2024 |
| Milosh Media Limited | Information & communication | 2021 |
| Milton 1 Limited | Professional & scientific | 2007 |
| Milton 2 Limited | Hospitality | 2007 |
| Mimax Projects Ltd | Construction | 2017 |
| Mind on Business Ltd | Wholesale & retail | 2025 |
| Mindful People Ltd | Administrative & support | 2024 |
| Mindwell Services Ltd | Administrative & support | 2024 |
| Minea V&L MEP Services Ltd | Construction | 2026 |
| Minerva 147 Ltd | Wholesale & retail | 2024 |
| Mini Workshop Ltd | Wholesale & retail | 2018 |
| Minraf Ltd | Transport & logistics | 2018 |
| MIR1977 Ltd | Construction | 2024 |
| Mireldan Freight Limited | Transport & logistics | 2015 |
| Miro Building Services Ltd | Construction | 2026 |
| Miron Construction Ltd | Construction | 2012 |
| Mirza Consultancy Ltd | Education | 2021 |
| Missenden Landscapes Limited | Administrative & support | 2017 |
| Mist&Co Ltd | Wholesale & retail | 2020 |
| Mistel Group Limited | Financial services | 2025 |
| Mistel Investments Ltd | Real estate | 2023 |
| Mistel Properties Limited | Real estate | 2025 |
| Misti Enterprises (UK) Limited | Wholesale & retail | 2017 |
| Misu&Coco Ltd | Transport & logistics | 2022 |
| Misz Transport Ltd | Transport & logistics | 2025 |
| Mitel Ltd | Transport & logistics | 2018 |
| Miti Steel Ltd | Construction | 2026 |
| Mititel Construction Services Limited | Construction | 2017 |
| MIU MIU Gems and Jewels Ltd | Wholesale & retail | 2024 |