| Hindsight Software Ltd | |
| Hinge Ltd | |
| Hinterview Ltd | |
| Hiper Ltd | Glasgow |
| Hiperactive.Net Ltd | Cambridgeshire |
| HiperCom Holding Ltd | |
| Hiperpool Ltd | |
| Hippo Digital Ltd | |
| Hirebolt | |
| Hired by Startups Ltd | |
| HireDeveloper.dev | |
| Hireserve Ltd | Hampshire |
| Hiro Capital 1, LLP | |
| HiSOFT | Isle of Wight |
| HistoCyte Laboratories Ltd | |
| Hit Search Ltd | Merseyside |
| Hitachi Cambridge Laboratory | |
| Hitachi Rail Ltd | |
| Hitch Design | West Midlands |
| Hitchman IT Solutions Ltd | Essex |
| Hitex (UK) Ltd | West Midlands |
| Hitmaker Ltd | |
| Hive Creative Ltd | |
| Hive Design Agency | |
| Hive19 | |
| HIVED Ltd | |
| HiveMQ | |
| Hivolt Capacitors Ltd | Derry and Strabane |
| Hiyield Ltd | |
| HJS Technology Ltd | |
| HK Web Solutions | |
| HKS Manpower Group Ltd | |
| HLB International Ltd | |
| HMA | |
| HMG.NET Ltd | South Lanarkshire |
| Hobb Computer Services Ltd | Staffordshire |
| Hobo Web | |
| Hoburne Business Systems | |
| Hodgkinson McCambridge Ltd | |
| Hofy Ltd | |
| Hogarth | |
| Hoge 100 Business Systems Ltd | Worcestershire |
| HOH Ltd | Gloucestershire |
| HOKO | |
| Hoko Design | |
| Hokodo Services Ltd | |
| Holdens Agency Ltd | |
| Holibob | |
| HolidayFox | |
| Holiferm | |