Tax payments are due quarterly. The first quarter is due February 1st and covers the months of January, February and March. The second quarter is due May 1st and covers the months of April, May and June. The third quarter is due August 1st and covers the months of July, August and September. The fourth quarter is due November 1st and covers the months of October, November and December. There is a ten day grace period. If the 10th falls on a weekend or a legal holiday you have until the next business day to make payment.