| Marcaz Ltd | Other services | 2020 |
| Marcegaglia Stainless Sheffield Ltd | Manufacturing | 2022 |
| Marceline&Leon Ltd | Wholesale & retail | 2016 |
| Marcelo's Ice Cream Ltd | Manufacturing | 2026 |
| Marcforce Limited | Construction | 1993 |
| March & MAY Limited | Manufacturing | 2004 |
| March 2021 Ltd | Health & social care | 2021 |
| Marcia Denta Limited | Transport & logistics | 2025 |
| Marcia Inn Bishopthorpe Ltd | Hospitality | 2013 |
| Marcia's ALL Nations Ltd | Hospitality | 2026 |
| Marco Island Developments Limited | Construction | 2014 |
| Marco Zerboni Limited | Other services | 2019 |
| Marco's Restaurant Ltd | Hospitality | 2013 |
| Marcolem Limited | Real estate | 2020 |
| Marcrest Limited | Construction | 1994 |
| Marcus Anderson Ltd | Administrative & support | 2022 |
| Marcus Dando Holdings Ltd | Financial services | 2021 |
| Marcus Reynolds Music Limited | Manufacturing | 2014 |
| Marcut Limited | Extraterritorial | 2008 |
| Mard Limited | Hospitality | 2024 |
| Marden Road Limited | Real estate | 2023 |
| Mardin Fresh Ltd | Hospitality | 2026 |
| Mardy Munch Ltd | Hospitality | 2025 |
| Marema Fashion Ltd | Wholesale & retail | 2025 |
| Marfona Ltd | Hospitality | 2016 |
| Margate Films Limited | Information & communication | 2017 |
| Margery Hill Limited | Professional & scientific | 2012 |
| Margo Brook Properties Limited | Real estate | 2015 |
| Margot Consultancy Limited | Arts & recreation | 2019 |
| Margrave Community Support Limited | Health & social care | 2026 |
| Marham Financial Solutions Limited | Professional & scientific | 2018 |
| Maria Clews Ltd | Professional & scientific | 2009 |
| Maria Frith Ecclesall HR Ltd | Other services | 2011 |
| Maria Market Ltd | Wholesale & retail | 2022 |
| Maria Mentoring Ltd | Professional & scientific | 2024 |
| Maria Restaurants Ltd | Hospitality | 2025 |
| Maria ZK Ltd | Wholesale & retail | 2025 |
| Marian Building Ltd | Construction | 2019 |
| Maria’S PUB Ltd | Hospitality | 2024 |
| Marie Quigley Ltd | Education | 2021 |
| Marigold Health Ltd | Health & social care | 2024 |
| Marimedics Limited | Health & social care | 2022 |
| Marina Lewycka Limited | Administrative & support | 2004 |
| Marina Medical Ltd | Health & social care | 2025 |
| Marinaa Ltd | Real estate | 2022 |
| Marine Sales Channel Limited | Administrative & support | 2003 |
| Marine Supply Chain Limited | Professional & scientific | 2008 |
| Marion Boyars Publishers Limited | Information & communication | 1975 |
| Marisa Roberts Limited | Other services | 2009 |
| Maritime Safety & Navigation Consultancy Ltd | Transport & logistics | 2020 |
| Marius Transport 26 Limited | Transport & logistics | 2019 |
| Mariusz Andrzejczak Ltd | Transport & logistics | 2014 |
| Marjolo Ltd | Professional & scientific | 2013 |
| Marjolo Partners Ltd | Professional & scientific | 2015 |
| Mark Andrew Lycett Limited | Extraterritorial | 2014 |
| Mark Barnsley Flooring Services Limited | Construction | 2014 |
| Mark Bell Consulting Limited | Administrative & support | 2022 |
| Mark Downing Consultancy Limited | Financial services | 2020 |
| Mark Fowler Limited | Professional & scientific | 2010 |
| Mark Fretwell Consulting Ltd | Other services | 2014 |
| Mark Mcalindon Limited | Health & social care | 2012 |
| Mark ROE Media Limited | Administrative & support | 2006 |
| Mark Rowley Ltd | Professional & scientific | 2013 |
| Mark Ryden Global Ltd | Information & communication | 2019 |
| Mark Stanley Consultancy Services Limited | Professional & scientific | 2010 |
| Mark Stocks Facade Ltd | Construction | 2016 |
| Mark Swift Enterprises Limited | Transport & logistics | 2016 |
| Mark Webber Limited | Information & communication | 2011 |
| Mark Whalley Group Limited | Professional & scientific | 2022 |
| Mark Your Space Ltd | Manufacturing | 2025 |
| Markbalance Limited | Extraterritorial | 1989 |
| Markbridge Limited | Real estate | 2017 |
| Markeb Media Ltd | Professional & scientific | 2024 |
| Marken Chemicals Ltd | Wholesale & retail | 2008 |
| Market Cross Properties (Selby) Limited | Real estate | 2004 |
| Market Infra Consulting Limited | Professional & scientific | 2016 |
| Market Sector Consolidation Limited | Professional & scientific | 2005 |
| Marketing and Business Planning Limited | Administrative & support | 2006 |
| Marketing Collaborative Ltd | Professional & scientific | 2025 |
| Marketing for Engineering Limited | Administrative & support | 2013 |
| Marketing Solutions Emea Limited | Professional & scientific | 2024 |
| Marketmakers International Limited | Administrative & support | 2020 |
| Marketmatrix Ltd | Wholesale & retail | 2024 |
| Marketology Ltd | Professional & scientific | 2014 |
| Markham Quay Management Limited | Households | 2003 |
| Markham Vale 6 Holdco Limited | Real estate | 2024 |
| Markham Vale 6 Propco Limited | Real estate | 2024 |
| Markham Vale 9 Holdco Limited | Real estate | 2025 |
| Markham Vale 9 Propco Limited | Real estate | 2025 |
| Marks Audio Solutions Ltd | Manufacturing | 2024 |
| Marktrails Ltd | Wholesale & retail | 2020 |
| Marlborough Estates Management Ltd | Real estate | 2011 |
| Marlon Primed Recovery Ltd | Health & social care | 2026 |
| Marlow Ellis Partnership Limited | Professional & scientific | 2014 |
| Marlow Packaging Limited | Manufacturing | 2010 |
| Marmaduke Health Care Limited | Health & social care | 2019 |
| Marmaduke's Cafe Deli Limited | Hospitality | 2012 |
| Marmaris Pizza Grill Ltd | Hospitality | 2022 |
| Maron Paint Services Limited | Construction | 2024 |
| Marples Homes Ltd | Real estate | 2026 |