No reversal of Cenvat while writing off inputs/WIP for period prior to introduction of provisions fo

Cenvat Credit : Rule 3(5B) providing for reversal on inputs/capital goods written off 'fully' was introduced only from 11-5-2007 and provision regarding 'partial' write-off was introduced only in year 2011; therefore, same could not be applied for period prior thereto to seek reversal on partially written of inputs/WIP