Taxpayer's income is IRA RMD and Social Security. RMD has Fed and State withholdings. In March, He sold rental property and realized a gain of $340,000.Factoring Capital Gains, Recapture , and Net Investmant taxes, total is estimated to be $70,000. Can he pay the $70,000 over four quarters or doe he have to pay the entire amount in the first quarter. This is my first time with Safe Harbor Rules.