For 2018 Fed tax refund, I elected applied it to 2019 estimated tax. Internet said it need to be applied to 2019 1st quarter by 4/15.? But I missed this date. Can I apply it to the 2nd and 3rd quarter? If so, how can I process it? I use www.eftps.gov to make online payment quarterly. Just simply minus the refund from my regular payment amount? Do I need to fill out any related form?