Charles and Joan Thompson file a joint return. In 2015, they had taxable income of $98,620 and paid tax of $16,604. Charles is an advertising executive, and Joan is a college professor. During the fall 2016 semester, Joan is planning to take a leave of absence without pay. The Thompsons expect their taxable income to drop to $79,500 in 2016. They expect their 2016 tax liability will be $11,594, which will be the approximate amount of their withholding. Joan anticipates that she will work on academic research during the fall semester.

During September, Joan decides to perform consulting services for some local businesses. Charles and Joan had not anticipated this development. Joan is paid a total of $31,500 during October, November, and December for her work. Use the appropriate Tax Rate Schedules.

a. What estimated tax payments are Charles and Joan required to make, if any, for tax year 2016?