Undisclosed income focused; stay period tolling ends when certified vacatur copy reaches the jurisdictional tax commissioner. The amendment narrows sub section (1) of section 158BFA to refer only to undisclosed income instead of 'total income including undisclosed income,' and replaces clause (ii) of sub section (4) to define the stay period as beginning on the date a court granted the stay and ending when a certified copy of the order vacating the stay is received by the jurisdictional Principal Commissioner or Commissioner; both substitutions are treated as having been made with effect from the stated commencement.