S.3121: A bill to amend the Internal Revenue Code of 1986 to allow the Secretary of the Treasury to waive the penalties for failure to disclose reportable transactions, and for other purposes.

Amends the Internal Revenue Code to modify provisions relating to the waiver of penalties for failure to disclose reportable transactions (i.e., transactions which have a potential for tax avoidance or evasion) to grant authority to the Secretary of the Treasury (instead of the Commissioner of Internal Revenue) to rescind or waive all or a portion of such penalties and to allow a waiver if there was reasonable cause for the failure to disclose such transactions and the taxpayer acted in good faith.