29 CFR § 20.55 - Second and subsequent notifications.
(a) In accordance with guidelines established by the Chief Financial Officer, the responsible agency head (or designee) shall send progressively stronger second and subsequent demands for payment, if payment or other appropriate response is not received within the time specified by the initial demand. Unless a response to the first or second demand indicates that a further demand would be futile or the debtor's response does not require rebuttal, the second and subsequent demands shall generally be made at 30-day intervals from the first, and shall state that a 6 percent per annum penalty will be assessed after the debt has been delinquent 90 days, accruing from the date it became delinquent. An agency head (or designee), however, in his or her sole discretion can send second and subsequent demands at shorter intervals. The second and subsequent demands shall identify the amount of interest then accrued on the debt, as well as administrative costs thus far assessed. In determining the timing of the demand letters, agencies should give due regard to the need to act promptly so that, if necessary, the debt may be referred in a timely manner to the Department of Justice for litigation. When the agency head (or designee) deems it appropriate to protect the government's interests (for example, to prevent the statute of limitations 28 U.S.C. 2415, from expiring), written demand may be preceded by other appropriate actions, including immediate referral for litigation.
(b) Agencies shall also include in their demand letters the notice provisions to debtors required by other regulations of the Labor Department, pertaining to waiver of the indebtedness, administrative offset, salary offset and disclosure of information to credit reporting agencies, to the extent that such inclusion is appropriate and practicable.