Iowa Code Title XV. Judicial Branch and Judicial Procedures [Chs. 595-686] § 633E.7. Disclaimer of rights of survivorship in jointly held property

a. If, during the deceased holder's lifetime, the deceased holder could have unilaterally regained a portion of the property attributable to the deceased holder's contribution without the consent of any other holder, a surviving holder may disclaim, in whole or in part, a fractional share of that portion of the property attributable to the deceased holder's contributions determined by dividing the number one by the number of joint holders alive immediately after the death of the holder to whose death the disclaimer relates.

b. For all other jointly held property, a surviving holder may disclaim, in whole or in part, a fraction of the whole of the property the numerator of which is one and the denominator of which is the product of the number of joint holders alive immediately before the death of the holder to whose death the disclaimer relates multiplied by the number of joint holders alive immediately after the death of the holder to whose death the disclaimer relates.