When you are annualizing, you can potentially get this result due to TurboTax's method of rounding that does not follow the IRS rules for rounding. Instead of summing the dollars-and-cents withholding amounts from each of the sources of withholding then rounding to the nearest dollar as instructed by the IRS, TurboTax rounds each separate item of withholding, then sums the resulting whole-dollar amounts. To determined the total whole-dollar amounts needed when annualizing withholding in TurboTax, take the amount of withholding from each source you've reported, round it to the nearest dollar, sum the rounded amounts, then split that sum into whole-dollar amounts among the four tax quarters.
