Quick answerIowa sells tax lien certificates for unpaid property taxes. Lien buyers can earn 2% per month / 24% per year, fixed by statute (Iowa Code 447.1); the rate is not bid down - bidders compete by bidding down the undivided interest percentage in the parcel they would take on a deed, and many counties assign contested parcels by random / rotational selection among registered bidders.. Redemption: The holder may serve a notice of expiration of the right of redemption after 1 year and 9 months from the sale; redemption ends 90 days after completed service of that notice (Iowa Code 447.9, 447.12), so the effective minimum hold is about 2 years. Sales: Annual tax sale on the third Monday in June in every county (Iowa Code ch. 446), with adjourned sales for unsold parcels thereafter. Governing law: Iowa Code chs. 446 (tax sale), 447 (redemption) and 448 (tax deeds), esp. 446.16, 447.1 and 447.9.