I do not believe this is universally correct. IRS Publication 505 has a worksheet (Worksheet 2-7) that is used to calculate annualized estimated quarterly tax payments for self employment situations that have variability throughout the tax year (e.g. seasonal employment). I have manually (6sjng Excel not in Turbotax) compared it to a constant quarterly estimated tax payment (Worksheet 2-1 frim the exact same publication, and they generate the same total yearly estimated tax payments to the dollar. The example I used had estimated tax payments that were a factor of 5 different from one quarter to the other.
