31 CFR 370.25: What rights do I have to terminate or suspend debit entries?

(a) General. If you are an investor account owner or deposit account owner, you generally may terminate or suspend one or more debit entries by notifying us orally or in writing at least three business days before the scheduled date of a transfer. In response to an oral notice, we may require you to give written notice, to be received by us within fourteen days of an oral notice. An oral notice ceases to be binding after fourteen days if you fail to provide the required written confirmation. A suspension will remain in effect for the duration you specify, but for no more than six months. The termination and suspension methods need not be recited in the authorization. These termination or suspension rights are in addition to those that you may have through your financial institution under Regulation E of the Board of Governors of the Federal Reserve System (12 CFR part 205).

(b) Exception. If you submit a debit entry authorization in conjunction with a Treasury auction tender for the purchase of a book-entry security, you cannot terminate or suspend a debit entry after the auction closes.