| Mark Smith Writing Services Ltd | Information & communication | 2021 |
| Mark Stringer Consulting Limited | Information & communication | 2017 |
| Mark Taylor Homes Limited | Construction | 2021 |
| Mark Turner Painting & Decorating Limited | Construction | 2014 |
| Mark UP Holdings (UK) Ltd | Financial services | 2016 |
| Mark Williams Flooring Ltd | Construction | 2020 |
| Markall Limited | Arts & recreation | 2023 |
| Markant Properties Ltd | Real estate | 2024 |
| Market Access & Reimbursement Solutions Limited | Administrative & support | 2012 |
| Market Global Ltd. | Wholesale & retail | 2022 |
| Market Lodge Store Ltd | Wholesale & retail | 2025 |
| Market Street Homes Limited | Real estate | 2021 |
| Marketing Communities CIC | Administrative & support | 2024 |
| Marketing Industry Limited | Professional & scientific | 2021 |
| Marketing the Change Limited | Information & communication | 2017 |
| Marketrix Ltd | Professional & scientific | 2005 |
| Markgee Design Ltd | Other services | 2020 |
| Markhams Limited | Professional & scientific | 1997 |
| Markhr Ltd | Administrative & support | 2020 |
| Markman Capital Limited | Hospitality | 2020 |
| Marko Consultancy and Fitness Ltd | Professional & scientific | 2019 |
| Marko Marketing Ltd | Information & communication | 2024 |
| Marko Promotions Ltd | Administrative & support | 2025 |
| Markone Properties Limited | Real estate | 2024 |
| Marks Experience Co Limited | Professional & scientific | 2019 |
| Marks Sparks Electrical Limited | Construction | 2025 |
| Markson Pharma Ltd | Health & social care | 2026 |
| Marl Coatings Holdings Ltd | Extraterritorial | 2020 |
| Marl Coatings Limited | Manufacturing | 2006 |
| Marl Properties Ltd | Real estate | 2025 |
| Marl Road Joinery & Fabrication Ltd | Other services | 2013 |
| Marlan Maritime Technologies Ltd | Professional & scientific | 2013 |
| Marlborough Street Property Limited | Real estate | 2025 |
| Marlby Code Limited | Information & communication | 2025 |
| Marldon Brickwork (NW) Ltd | Construction | 2015 |
| Marldon Legal Services Limited | Financial services | 2012 |
| Marles Holiday Homes Limited | Hospitality | 2021 |
| Marles Property Holdings Limited | Real estate | 2021 |
| Marley MAX Ltd | Hospitality | 2019 |
| Marley Technologies Ltd | Wholesale & retail | 2020 |
| Marli HV Ltd | Construction | 2019 |
| Marlia Developments Ltd | Extraterritorial | 2023 |
| Marlinga Limited | Real estate | 2017 |
| Marmalade Bistro Ltd | Hospitality | 2017 |
| Marmaris Finch Lane L14 Ltd | Hospitality | 2025 |
| Marmaris Food Station Ltd | Hospitality | 2024 |
| Marmarise Foodstore Limited | Hospitality | 2010 |
| Marmarise L3 Store Limited | Hospitality | 2022 |
| Marmarise Nice Pizza Ltd | Hospitality | 2022 |
| Marmma Ltd | Real estate | 2023 |
| Marnon Ltd | Construction | 2019 |
| Marosa Ltd. | Professional & scientific | 2015 |
| Marow Pizzas Ltd | Hospitality | 2023 |
| Marr Water Limited | Manufacturing | 1995 |
| Marra & Sons Ltd | Administrative & support | 2021 |
| Marrakech Trading Ltd | Hospitality | 2017 |
| Marram Business Services Ltd | Manufacturing | 2026 |
| Marram Formby Ltd | Households | 2024 |
| Marrionpj Ltd | Construction | 2025 |
| Marrison Group Limited | Wholesale & retail | 2013 |
| Marrow Property Ltd | Real estate | 2024 |
| Mars & Stars Ltd | Real estate | 2024 |
| Mars Retail L8 Ltd | Wholesale & retail | 2025 |
| Marsden Grange 2 Limited | Health & social care | 2024 |
| Marsh Lane Limited | Households | 2024 |
| Marshall & Family (Liverpool) Ltd | Hospitality | 2010 |
| Marshall Builders Ltd | Construction | 2011 |
| Marshall Electrical Installations Ltd | Construction | 2023 |
| Marshall Land & New Homes Ltd | Real estate | 2023 |
| Marshall Leisure Group Ltd | Extraterritorial | 2016 |
| Marshall Moore Limited | Administrative & support | 1996 |
| Marshall Property (Rodney ST) Limited | Real estate | 2022 |
| Marshall Property Construction Limited | Construction | 2005 |
| Marshall Restoration Ltd | Construction | 2008 |
| Marshall Wilson Ltd | Professional & scientific | 2005 |
| Marshall Zoing Limited | Financial services | 2002 |
| Marshallets Limited | Real estate | 2011 |
| Marshils Wine Ltd | Wholesale & retail | 2021 |
| Marshmallow Beauty Ltd | Wholesale & retail | 2021 |
| Marshy's Couriers Limited | Transport & logistics | 2025 |
| Marston Electrical Services Ltd | Construction | 2015 |
| Marta.Kska Limited | Manufacturing | 2023 |
| Martam Ltd | Wholesale & retail | 2023 |
| Martelli Giovanni Ltd | Hospitality | 2023 |
| Martial Arts Minds Matter CIC | Arts & recreation | 2025 |
| Martico UK Limited | Transport & logistics | 2021 |
| Martin Bencher (UK) Limited | Transport & logistics | 2014 |
| Martin Dash Engineering Limited | Professional & scientific | 2015 |
| Martin Green Upholstery Limited | Other services | 2003 |
| Martin John School Services Ltd | Wholesale & retail | 2015 |
| Martin Lacy HGV Limited | Transport & logistics | 2023 |
| Martin Mechanical Engineering Ltd | Wholesale & retail | 2003 |
| Martin-Cooke (Car Repairs) Limited | Wholesale & retail | 1984 |
| Martina&Mv Limited | Transport & logistics | 2017 |
| Martina&Mv Realty Ltd | Real estate | 2025 |
| Martindale's Technical Services Limited | Professional & scientific | 1968 |
| Martineau Place Hotels Limited | Administrative & support | 2011 |
| Martineau Place Limited | Administrative & support | 2011 |
| Martinflipflop Ltd | Wholesale & retail | 2023 |
| Martinshouse Ltd | Real estate | 2023 |