Wis. Admin. Code Department of Employee Trust Funds ETF 20.30
Pursuant to s. 40.08(7) (c), Stats., if an annuity under s. 40.23, 40.24, 40.63, or 40.73, Stats., is underpaid by more than $2 in a month, and if that underpayment is uncorrected for 12 or more months, then the payment to the annuitant to correct the underpayment shall include interest at 0.4 % per month for each full month between the date the underpayment occurred and the date the retroactive correction is paid. The interest due shall be calculated separately for each month's underpaid amount. For purposes of this section, "full month" means the period from any date in a month to the corresponding date in the next month, or to the end of the month if there is no corresponding date.
Wis. Admin. Code Department of Employee Trust Funds ETF 20.30
This rule (CR 09-057) changes the calculation of interest on underpayments to conform to s. 40.08(7) (c), Stats., and pay monthly interest on a particular month's underpayment until it is corrected.