The pretax yield that a taxable bond needs to possess for its yield to be equal to that of a tax-free municipal bond. This calculation can be used to fairly compare the yield of a tax-free bond to that of a taxable bond in order to see which bond has a higher applicable yield.  Also known as "after-tax yield." 

|||For example, if a tax-free bond has a yield of 20% and the tax rate is 10%, a taxable bond would need a pretax yield of 22.2% (20% / 90%) in order to be considered an equivalent investment. Therefore, all bonds with the same risk but with a pretax yield of less than 22.2% should be considered inferior investments compared to the 20% municipal bond.