$300 - Assuming equal distribution of income for the full calendar year, estimated tax for each period is calculated by dividing the annual estimated tax due by the no. of periods which is 4. Since the estimated tax for Year 3 is $1,600, the estimated tax due per period is $400 when annualized. The $500 of overpayment from year 3, would first be applied to the firs quarter, i.e., April 15, year 3 for $400 and the remaining $100 would be applied to second Quarter, i.e.., June 15, year 3. Since the balance due for second quarter is computed as $400, Lake would be required to pay the remaining $300 for this period.