Three Requirements
(1) Failure to complete is due to circumstances beyond your control -- job loss, disability, death of spouse, medical emergency.
(2) Unsecured creditors received at least what they would have gotten in a Chapter 7 liquidation (best interest test).
(3) Modification of the plan is not practicable -- you have tried or it would not solve the problem.
Key Difference from Full Discharge
The hardship discharge does NOT include the Chapter 13 superdischarge benefits. Debts under 523(a)(2) (fraud), (4) (fiduciary fraud), and (6) (willful injury) survive a hardship discharge, just as they would in Chapter 7.
This means the hardship discharge is essentially the same scope as a Chapter 7 discharge, but obtained through Chapter 13.
Learn more about hardship discharge
Hardship Discharge Guide