Interest under sections 215 and 217 is chargeable only up to the date of the original assessment despite subsequent reassessments. Interest under sections 215 and 217 is computed from the first day of April next following the previous year up to the date of the regular assessment; where an original assessment is cancelled under section 146 or set aside and a fresh assessment framed, interest is chargeable only up to the date of the original (first) assessment, since the statutory reference to the regular assessment refers to the initial assessment on the return, distinct from later reassessments.