64:44:01:05Determination of credit period.

The first day of a credit period is the day following the date of invoice, and the 30-day period expires at midnight the thirtieth day following the date of invoice, after which payment is delinquent. However, no remittance made by mail is considered delinquent if it is affirmatively established that the envelope in which the remittance was transmitted bears the postmark of the thirtieth day following the date of invoice.

Source: 1 SDR 44, effective December 6, 1974; 13 SDR 129, 13 SDR 134, effective July 1, 1987.