2. Yes, the assessee can legitimately seek exclusion of the period spent bona fide prosecuting the writ petition before the High Court, but I would not say that exclusion is automatic.
The legal foundation should be presented in this order:
Section 112, CGST Act
limitation and power to condone sufficient cause
Section 29(2), Limitation Act, 1963
applicability of Sections 4-24 to special-law limitation, subject to its conditions
Section 14, Limitation Act, 1963
exclusion of time spent prosecuting the earlier proceeding with due diligence and in good faith
Alternatively / additionally, Section 112 proviso
condonation on sufficient cause.
And the factual foundation is:
GSTAT was not constituted/available assessee did not sleep over its remedy assessee approached High Court writ remained pending GSTAT subsequently became available assessee seeks withdrawal with liberty immediately files GSTAT appeal.
That is a reasonably strong position, provided the chronology and the High Court order support it.
One caution
I would not presently state as a proposition of settled law that "Section 14 automatically excludes the entire period of the writ petition from GSTAT limitation." The exact applicability of Section 14 to the Section 112 CGST appeal requires judicial support and depends on the precise facts and the manner in which the writ proceedings were pursued/disposed of.
The safer litigation strategy is to plead Section 14 as the primary exclusion argument and Section 112's sufficient-cause condonation power as an independent alternative.
In continuation of my reply at serial no.4 above,
If it is so, the time-bar aspect already covered up while filing writ petition with the High Court and thus you do not need the shelter of any case law.