| Moremax Business Solutions Ltd | Information & communication | 2025 |
| Moreprop Limited | Real estate | 2026 |
| Moreslikan Group Co. Ltd | Extraterritorial | 2020 |
| Morfa Developments Limited | Real estate | 1972 |
| Morgan Abrasives & Industrial Supplies Limited | Manufacturing | 1992 |
| Morgan and Mumford Property Services Limited | Real estate | 2005 |
| Morgan Channing Consultancy Ltd | Professional & scientific | 2025 |
| Morgan Cole LLP | | 2010 |
| Morgan Denton Jones Limited | Professional & scientific | 2011 |
| Morgan Forest Products Limited | Administrative & support | 2006 |
| Morgan Griffin Ltd | Real estate | 2021 |
| Morgan Jupe Limited | Wholesale & retail | 2012 |
| Morgan Lighting Services Ltd | Construction | 2019 |
| Morgan Peterson Limited | Financial services | 2010 |
| Morgan Project Solutions Ltd. | Construction | 2012 |
| Morgan Properties South Wales Limited | Real estate | 2011 |
| Morgan Property Cardiff Limited | Real estate | 2020 |
| Morgan Social Care Limited | Health & social care | 2018 |
| Morgan Street Dental Practice Ltd | Health & social care | 2010 |
| Morgan Structural Wales Ltd | Professional & scientific | 2022 |
| Morgan-Genus Ltd. | Wholesale & retail | 2014 |
| Morganbys Capital Ltd | Financial services | 2024 |
| Morgans Joinery Limited | Construction | 2019 |
| Morgans Psychology Ltd | Education | 2023 |
| Morganti Electrical Services Ltd | Construction | 2018 |
| Morgenstern & Major Ltd | Professional & scientific | 2018 |
| Morgenstern & Partners Ltd | Administrative & support | 2025 |
| Morgwood Reporting Ltd | Health & social care | 2024 |
| Morianu Engineering Ltd | Professional & scientific | 2021 |
| Morina&Co Ltd | Information & communication | 2017 |
| Morini and Bossi Tools Europe Limited | Manufacturing | 2019 |
| Morinv Ltd. | Wholesale & retail | 2025 |
| Morja Catering Ltd | Hospitality | 2026 |
| Morley Animation Limited | Information & communication | 2018 |
| Morningedge Technologies Ltd | Information & communication | 2025 |
| Mornington Court Rumney Limited | Households | 2015 |
| Morocco Fruit & VEG Limited | Wholesale & retail | 2019 |
| Morol Security Limited | Administrative & support | 2026 |
| Morora Limited | | 1923 |
| Moroski Ltd | Wholesale & retail | 2025 |
| Morp Central Ltd | Professional & scientific | 2025 |
| Morris & Hannah Limited | Information & communication | 2009 |
| Morris GAS & Heating Ltd | Construction | 2024 |
| Morris Holmes Ltd | Construction | 2022 |
| Morris Paley Wealth Management Limited | Other services | 2016 |
| Morris Property and Development Ltd | Real estate | 2022 |
| Morris Property Partners Limited | Real estate | 2025 |
| Morrish & Co Limited | Professional & scientific | 2025 |
| Morrocan Kaftan Ltd | Wholesale & retail | 2025 |
| Mort Solutions Ltd | Wholesale & retail | 2018 |
| Mortajinetech Ltd | Other services | 2025 |
| Mortensen Skarsgard Limited | Wholesale & retail | 2017 |
| Mortgage & Finance Brokers Ltd | Financial services | 2025 |
| Mortgage Advice Supermarket UK Ltd | Financial services | 2023 |
| Mortgage Maison Limited | Financial services | 2024 |
| Mortgage Metrics Ltd | Information & communication | 2021 |
| Mortimer Engineering Limited | Professional & scientific | 2015 |
| Mortlock Advisory Limited | Professional & scientific | 2026 |
| Mortlock Ventures Ltd | Real estate | 2024 |
| Morton Harbour Ltd | Health & social care | 2017 |
| Mortzz Ltd | Information & communication | 2025 |
| Morvexa (UK) Brand Co., Ltd | Wholesale & retail | 2025 |
| Morvion Ltd | Education | 2025 |
| Morwell Talent Solutions Limited | Administrative & support | 2024 |
| MOS Property Investments Ltd | Real estate | 2020 |
| MOS Studio Limited | Real estate | 2025 |
| Mosaic Analytics Ltd | Information & communication | 2019 |
| Mosaic Clothing Limited | Wholesale & retail | 2002 |
| Mosaic Mirror Home Ltd | Wholesale & retail | 2025 |
| Moscone PC | | 2014 |
| Moseley Catering Limited | Hospitality | 2025 |
| Moses Investments Limited | Real estate | 2024 |
| Moshi Moshi Communication Ltd | Professional & scientific | 2020 |
| Moslo Ltd | Wholesale & retail | 2019 |
| Mosmer PC | | 2018 |
| Moss Rose Cottage C.I.C. | Manufacturing | 2021 |
| Mosshoping Ltd | Wholesale & retail | 2025 |
| Mossoyflower Ltd | Information & communication | 2025 |
| Mossy Ventures Ltd | Professional & scientific | 2022 |
| Mossymill Ltd | Wholesale & retail | 2025 |
| Most. HQ Limited | Administrative & support | 2019 |
| Mosta Marine Services Ltd | Manufacturing | 2025 |
| Mostafa Group Ltd | Professional & scientific | 2025 |
| MOT Cardiff Ltd | Wholesale & retail | 2011 |
| Motaworx Service Limited | Wholesale & retail | 2017 |
| Motech Autos Ltd | Wholesale & retail | 2025 |
| Motel Nights Limited | Hospitality | 2019 |
| Mother Hubbard's (the Wales) Ltd | Hospitality | 2022 |
| Mother Hubbard's Franchising (the Wales) Ltd | Hospitality | 2022 |
| Mother Hubbard's Group (the Wales) Ltd | Hospitality | 2022 |
| Mother Hubbard's Holdings (the Wales) Ltd | Hospitality | 2022 |
| Mother Hubbards Cardiff Limited | Hospitality | 2026 |
| Mother Marys Venues Ltd | Hospitality | 2024 |
| Mother Nature Restaurant Limited | Hospitality | 2020 |
| Motherearthmakes Ltd | Wholesale & retail | 2025 |
| Motif Agency Ltd | Information & communication | 2014 |
| Motio Camps Ltd | Education | 2026 |
| Motion Manor Ltd | Information & communication | 2021 |
| Motion Movement Studio Ltd | Arts & recreation | 2026 |
| Motion Plant Hire and Groundworks Ltd | Administrative & support | 2019 |