Payment of Withheld Income Tax 1 Due Date for Payment

Income tax withheld by a withholding agent shall in principle be paid by the 10th of the month following the month in which the income subject to withholding was paid.
If the due date is a Saturday, Sunday, or holiday, the next business day shall be the due date.
If payment is not made by the due date, the withholding agent may in principle have to pay delinquent tax and additional tax for non-payment.

（上記　国税庁ＨＰより引用）