| MadeByPi Ltd | |
| MadeByShape Ltd | Greater Manchester |
| MadeFrom | Greater London |
| MadeSmarter | |
| Madgex Ltd | East Sussex |
| Madhouse Media Ltd | |
| MadLab | |
| Magdalene Ltd | Cambridgeshire |
| Magdrive | |
| Magenta Electronics Ltd | Staffordshire |
| Magic Web Solutions | Kent |
| Magic5 Software | |
| Magicard Ltd | Dorset |
| MagicFuse | |
| Magin Web Design | |
| Maginus Software Solutions | Greater Manchester |
| Maglabs | |
| MagnaCom Ltd | Renfrewshire |
| Magnetic | |
| Magnitude Biosciences Ltd | |
| Magnum Enterprises | |
| Magora | |
| Magpie Education | |
| Magrathea-telecom | Berkshire |
| Magstim | |
| Maguires | |
| Mahaz Tech Enterprise Ltd | |
| MaidSafe.net Ltd | |
| Maidstone Technology | |
| Mailbox Internet | West Yorkshire |
| Mailchain Ltd | |
| Mailercloud | |
| Mailgate Ltd | Suffolk |
| mailingmanager | Northamptonshire |
| MailOrderWorks | Essex |
| Mailosaur Ltd | |
| Main Menu | |
| Maine Business Systems plc | West Midlands |
| Mainframe Computer Services Ltd | Lancashire |
| Mainstream Digital Ltd | Gloucestershire |
| MainStreet Consulting | |
| Maintel | Greater London |
| Majenta Solutions | West Midlands |
| Majestic | |
| Majestic Interactive Ltd | West Yorkshire |
| Major Custom Computing | |
| Major Digital | East Sussex |
| Make Digital Marketing Ltd | |
| Make Do | South Yorkshire |
| Make it POP | |