234A. (1) Where the return of income for any assessment year under sub-section (1) or sub-section (4) of section 139, or in response to a notice under sub-section (1) of section 142, is furnished after the due date, or is not furnished, the assessee shall be liable to pay simple interest at the rate of one per cent for every month or part of a month comprised in the period commencing on the date immediately following the due date, and,—
(a) where the return is furnished after the due date, ending on the date of furnishing of the return; or
(b) where no return has been furnished, ending on the date of completion of the assessment under section 144,
on the amount of the tax on the total income as determined under sub-section (1) of section 143, and where a regular assessment is made, on the amount of the tax on the total income determined under regular assessment, as reduced by the amount of,—
(i) advance tax, if any, paid;
(ii) any tax deducted or collected at source;
(iii) any relief of tax allowed under section 90 on account of tax paid in a country outside India;
(iv) any relief of tax allowed under section 90A on account of tax paid in a specified territory outside India referred to in that section;
(v) any deduction, from the Indian income-tax payable, allowed under section 91, on account of tax paid in a country outside India; and
(vi) any tax credit allowed to be set off in accordance with the provisions of section 115JAA or section 115JD.
Note the underlined words.
234A interest is leviable on total income determned in the regular assessment, which refers to 143(3) assessment.
Hope that addresses the issue.