| Metway Electrical Industries Ltd | East Sussex |
| Mevrik | |
| Meyertech Ltd | Greater Manchester |
| MF Communications Ltd | Kent |
| MF Telecom Services | |
| MFD Capacitors (1991) Ltd | Wrexham County Borough |
| MFDevCo | |
| MFX (microfluidx Ltd) | |
| MG Media Solutions | Gwynedd |
| MGCSoft | Greater Manchester |
| MGH Scotland Ltd | North Lanarkshire |
| MGT Design Ltd | Northamptonshire |
| mGuru | Bedfordshire |
| Mgy Digital Ltd | |
| MH MCR | |
| Miappi Ltd | |
| Mica Technology UK Ltd | Kent |
| Michael Davey Consulting Ltd | |
| Michael J. Stewart SEO Consultant & Google Ads Manager | |
| Michael Maclean | |
| MICRAMED Ltd | |
| Micregen Ltd | |
| Micrima Ltd | |
| Micro Drone | |
| Micro Focus | Berkshire |
| Micro Pro | |
| Micro Technology Consultants | North Lanarkshire |
| Micro-Tec Services | Norfolk |
| Micro2 | |
| Micro:bit Educational Foundation | |
| MicroAngelo | |
| Microapl Ltd | East Sussex |
| Microbiotica Ltd | |
| Microcom Systems Ltd | |
| Microcosm Ltd | Bristol |
| Microdec | Essex |
| MicrofluidX Ltd | |
| Micromat International | Cambridgeshire |
| Micron Data Solutions Ltd | Norfolk |
| Micron Web Design | Warwickshire |
| Micropathology Ltd | |
| Microplate Dx Ltd | |
| Micropore Technologies Ltd | |
| Micropraxis | Cambridgeshire |
| MicroProcessor Engineering Ltd | Hampshire |
| Microsaic Systems plc | |
| Microsec Ltd | Hampshire |
| MicroSense Technologies Ltd | |
| Microsmiths Ltd | Buckinghamshire |
| Microsoft United Kingdom | Berkshire |