Any show-Cause-Notice calling upon a dead person to defend himself is void-ab-initio. Any Order-In-Original confirming demand - resulting from such SCN - is also void-ab-initio.
Thereby, any recovery proceedings initiated against legal heirs against above-said OIO is bad in law and illegal.
Despite knowing above-said factual and legal position, if Dept. still persists with recovery proceedings on the basis of such OIO, the legal heir/s can approach jurisdictional High Court and get recovery-proceedings squashed.
All above are strictly personal views of mine and the same should not be construed as professional advice / suggestion.