1) Dereliction 
Failure to perform some act which should have been performed.
Failure to perform a duty or carry out an act when under legal obligation
The failure to act when a duty to act existed. Compare: misfeasance, malfeasance
Failure to act when duty required. Compare misfeasance.
[n] - a failure to act when under an obligation to do so
noun a failure to act when under an obligation to do so; a refusal (without sufficient excuse) to do that which it is your legal duty to do
the omission of some act that ought to have been performed. Cf.(def. 2).