| Habu | |
| Hack The Box | |
| Hackajob | Greater London |
| Hackquarters | |
| Hacktivlabs | |
| Hadean | |
| Hage Ltd | Gloucestershire |
| Haiper | |
| HaiX | |
| Halcyon Optical Services | Hampshire |
| Hale Insttruments Ltd | Greater Manchester |
| Haleon plc | |
| Halfhead Design | Cambridgeshire |
| Hallam Internet Ltd | Nottinghamshire |
| Hallmark Consumer Services | Leicestershire |
| Hallmark Electronics Ltd | Staffordshire |
| hallmarkdesign | East Sussex |
| Halo System | Devon |
| HaloITSM | |
| Hamilcar Capital Ltd | |
| Hamillroad Software Ltd | Cambridgeshire |
| Hamilton Rentals | Berkshire |
| Hamiltonian Dynamics | |
| Hampshire Business Computers | Hampshire |
| Hampton & Associates Ltd | |
| HANDD Business Solutions | Berkshire |
| Handpoint | |
| Hands-On Computer Solutions Ltd | Greater Manchester |
| HandsHQ Ltd | |
| Handtec | Cambridgeshire |
| Hangar 51 | |
| Hanlon Software Solutions | Nottinghamshire |
| Hannah Blair | |
| Hanover | |
| Hanson Search | |
| Hanson Web Design | Hertfordshire |
| Haoma Medica Ltd | |
| hape Technical Consulting Ltd | |
| Hapony Ltd | |
| Happaning | |
| Happen Software | |
| Happy Finish Ltd | |
| Happy Giraffe Group Ltd | |
| Hara Digital | |
| Harborne Computers | |
| Harborne Web Design Ltd | West Midlands |
| Harbr | |
| Harbr Group Ltd | |
| Hardball Games Ltd | |
| Hardcat | Surrey |