| Melf Computing Ltd | Kent |
| Melford Technologies Ltd | Buckinghamshire |
| Melius Cyber | |
| Melon Design & Marketing Ltd | Buckinghamshire |
| Melt Creative Ltd | |
| Melted Media Ltd | Cheshire |
| Melton IT Services Ltd | Greater Manchester |
| MemberGate Ltd | East Riding of Yorkshire |
| Memgraph Ltd | Greater London |
| MemoTech Ltd | Cambridgeshire |
| Memset Ltd | Surrey |
| Mendelian | |
| Meniga Ltd | |
| Menlo Park Recruitment | |
| Menora | |
| Mentat Innovations Ltd | Greater London |
| Mention Me Ltd | |
| Mentionlytics Ltd | |
| Mentor Computer Systems Ltd | Bedfordshire |
| Mentor Digital | |
| menusandblocks Ltd | Staffordshire |
| Menzies Distribution Ltd | |
| Meor Design | |
| Mercato Solutions Ltd | |
| Mercaux | |
| Merchant Agency | |
| Merchant Software Ltd | Glasgow |
| Mercia Real Estate | |
| Mercia Semiconductor Ltd | |
| Mercuri GP, LLP | Greater London |
| Mercury Systems Engineers Ltd | |
| Mereo BioPharma Group plc | |
| Merge | |
| MergerLinks Ltd | |
| Meridian Legal Systems Ltd | |
| Merisis Technology Ltd | |
| Merit Software | |
| Meritsoft | |
| Merlin Business Software Ltd | Derbyshire |
| Merlin Software Ltd | South Yorkshire |
| Mersey Internet | Merseyside |
| Merseyside Web Design | Merseyside |
| Merula Ltd | Cambridgeshire |
| Merxin Ltd | |
| Mesenbio | |
| Mesh-AI | |
| Mesmerise Global Ltd | |
| Mesoform Ltd | |
| MessageSpace | |
| MessageSpace | |