Which period shall be considered for interest under Section 234A if the return is not furnished in re-assessment?

Interest under section 234A accrues from the day after notice expiry until completion of re-assessment.

Where a return is required by a notice under Section 148 but is not furnished, interest under Section 234A is charged from the day after the expiry of the time allowed under the notice until the date of completion of re-assessment, and is calculated on the amount by which tax determined on re-assessment exceeds the tax determined in the completed assessment.