From the IRS Internal Revenue Service: Publication 505 According to the IRS, http://www.irs.gov/publications/p505/ch02.html http://www.irs.gov/publications/p505/ch02.html#d0e5961 Estimated Tax Payment Worksheet Specific Payment Due Date http://www.irs.gov/publications/p505/ch02.html IRS Publication 505 http://www.irs.gov/publications/p505/ch02.html Publication 505 http://www.irs.gov/publications/p505/ch02.html According to the IRS federal estimated tax payments are due on this schedule IRS Pub 505 specific payment due date http://www.irs.gov/publications/p505/ch02.html http://www.irs.gov/publications/p505/ch02.html http://www.irs.gov/publications/p505/ch02.html http://www.irs.gov/publications/p505/ch02.html http://www.irs.gov/publications/p505/ch02.html every quarter due http://www.irs.gov/publications/p505/ch02.html payment periods http://www.irs.gov/publications/p505/ch02.html http://www.irs.gov/publications/p505/ch02.html due http://www.irs.gov/publications/p505/ch02.html http://www.irs.gov/publications/p505/ch02.html http://www.irs.gov/publications/p505/ch02.html#d0e5923 https://www.irs.gov/publications/p505/ch02.html#d0e6371 http://www.irs.gov/publications/p505/ch02.html https://www.irs.gov/publications/p505/ch02.html instructions for calculating AGI https://www.irs.gov/publications/p505/ch02.html Chapter 2 of Publication 505 special rule, under "Higher Income Taxpayers" Worksheet 2-9 IRS New Tax Rates http://www.irs.gov/publications/p505/ch02.html Internal Revenue Service: Estimated Tax for 2012 http://www.irs.gov/publications/p505/ch02.html Publication 505 http://www.irs.gov/publications/p505/ch02.html special rule, under "Higher Income Taxpayers" IRS general rule http://www.irs.gov/publications/p505/ch02.html estimated earnings taxes general rule http://www.irs.gov/publications/p505/ch02.html http://www.irs.gov/publications/p505/ch02.html IRS website http://www.irs.gov/publications/p505/ch02.html#d0e5961 From the IRS http://www.irs.gov/publications/p505/ch02.html handy resource