The Taxpayer paid the gross receipts tax due for February 2000 eleven days late and was assessed penalty and interest by the Department. The Taxpayer paid the penalty amount due but not the interest amount assessed. The Taxpayer protested the penalty amount assessed, claiming the Department incorrectly assessed interest for an entire month when it should have assessed interest for only the period of time the payment was late (11 days). Section 7-1-67 NMSA 1978 governs the imposition of interest and provides that interest is to be calculated on a monthly, not a daily basis. Held: The Department correctly assessed one month’s interest on the Taxpayer’s late payment of gross receipts tax, eleven days after the due date. Protest Denied.