Ind. Code § 6-8.1-9.5-11

Sec. 11. If set off is sought pursuant to the provisions of this chapter against the combined refund of taxpayers who have previously filed a combined return, the entire refund is subject to set off unless there is a timely defense raised by a co-refundee who is not a debtor as defined in this chapter. If a timely defense is raised that the refund is based on a combined application of a debtor and a nondebtor, then set off shall only be effected against the debtor's share of the refund.