municipal corporation, or a State child support enforcement agency, including a lien arising by operation of law for overdue child support or an order to freeze the assets in an account, to effect a garnishment against a debtor. (vi) Lookback period The term lookback period means the two month period that begins on the date preceding the date of account review and ends on the corresponding date of the month two months earlier, or on the last date of the month two months earlier if the corresponding date does not exist. . (B) Application of certain rules