(1) Joint estimated tax payments may not be made after the death of either spouse. The surviving spouse must re-compute his or her estimated tax for the remainder of the year and pay separate installments for each remaining installment due date.

(2) Estimated tax payments are not required after the date of death for a deceased taxpayer.

(3) If a joint return is filed for the last tax year, the taxpayers' joint estimated tax payments may be applied on the return.

(4) If separate returns are filed for the last tax year of a deceased spouse, any joint estimated tax payments must be split equally.