To the best of my knowledge, there was a grace period of one day given for electronic payments, primarily because they clear immediately as compared to payment by a cheque. The circulars for the grace period were only advisory to the field officers, advising them not to take legal action on minor delays. In case of repeated delays, this grace period, to my knowledge, would not apply. In any case, there is no grace period in the online systems which compute interest for any delay.