| Level E Research | |
| Level39 | |
| Lever Technology Group plc | West Yorkshire |
| Leverate | |
| Levicept Ltd | |
| Levy McCallum | |
| Lewes SEO | |
| Lewis Bisland | Edinburgh |
| Lewis Digital | |
| Lewis Sweeney | |
| Lewisham College | |
| LEX Diagnostics Ltd | |
| Lexacom | Oxfordshire |
| Lexcom Systems Ltd | |
| Lexden Computer Services Ltd | Suffolk |
| LexiaUK Ltd | Tyne and Wear |
| LexisClick Online Marketing | Dorset |
| LexisNexis UK | |
| Lexoo | |
| Lexoo Ltd | |
| Lexverify Ltd | |
| LGC Biosearch Technologies | |
| LGN Innovations Ltd | |
| Lhasa Ltd | |
| Liam Pedley Design | |
| Libertas Solutions | Belfast |
| Libertus Solutions | Surrey |
| Liberty Global Holdings Ltd | |
| Liberty Marketing | |
| LIBF Ltd | |
| Libra Investment Services Ltd | |
| Libris Systems | |
| Libryo Ltd | Greater London |
| Libyano | Greater London |
| Lichfield Web Design | Staffordshire |
| Lickd Ltd | |
| Life IQ | |
| Life Science Group Ltd | |
| Life Sciences Hub Wales | |
| Lifebit | |
| LifeCycle Software Ltd | Berkshire |
| Lifehack | |
| Lifelancer | |
| Lifelight | |
| Lifetime Training Group | |
| LIFNano RX Ltd | |
| Lifology | |
| Lift | Greater London |
| LIfT BioSciences Ltd | |
| Lifted | |