The IRS assumes that all income is earned evenly throughout the year, so payments must also be made equally throughout the year. Therefore, the default assumption is that you owed 1/4 of the estimated taxes in April, 1/4 in June, 1/4 in September and 1/4 by January 15. Because you did not make estimated payments in April or June, TurboTax thinks you owe a penalty.
You should be able to sort this out by using form 2210 the penalty estimation form and telling the program to use the “annualized” method. With the annualized method, you report your income actually earned and your taxes actually paid in the 4 quarters of the year, to show that you paid the right amount of taxes for the amount of income earned in each quarter. if TurboTax doesn’t automatically take you to this form, it should be listed on the page for “other tax situations“.
