27 CFR § 70.81 - Notice and demand for tax.
(a) General rule. Where it is not otherwise provided by provisions of 26 U.S.C. enforced and administered by the Bureau, the appropriate TTB officer shall, after the making of an assessment of a tax pursuant to § 70.71 of this part, give notice to each person liable for the unpaid tax, stating the basis for the tax due, the amount of tax, interest, additional amounts, additions to the tax and assessable penalties, and demanding payment thereof. Such notice shall be given as soon as possible and within 60 days. However, the failure to give notice within 60 days does not invalidate the notice. Such notice shall be left at the dwelling or usual place of business of such person, or shall be sent by mail to such person's last known address.
(b) Assessment prior to last date for payment. If any tax is assessed prior to the last date prescribed for payment of such tax, demand that such tax be paid will not be made before such last date, except where it is believed collection would be jeopardized by delay.