Schedule SE Line 4a (and similarly for Line 5b) have us multiply our self-employment net profit by 0.9235 to, er, approximate our net earnings, which is how much our self-employment net profit will be after one half of the self-employment tax is subtracted. This approximate net earnings is then used to compute the self-employment tax, half of which is subtracted from our Schedule C net profit to give our actual net earnings.
It is probably not surprising to you that the value of the reduction when multiplying by 0.9235 and the half of the actual Schedule SE tax are not the same. That is, we are failing to solve this circular math accurately. Nonetheless, this could be solved with an exact calculation, which is a little harder but very much doable. Why isn't the exact approach used? Here's the math:
- Let C = Schedule C net profit plus Church-employee income that had no social security withholding.
- Let L = $176,100 = the 2025 income limit for the social security tax.
- Let W = all your wages plus other income that was already subject to the social security tax.
- Let R = L - W (but not less than zero) = how much remaining income can be subject to the social security tax.
We want to compute: N = Net Earnings = C minus half of the SE tax. We compute:
- N1 = C / 1.0765.
- N2 = (C - (0.062 * R)) / 1.0145.
- N = LargerOf(N1, N2).
N is the the exact value for net earnings. That is, it will be exactly consistent with the self-employment tax that is subsequently computed from it. (Well, if we round to the nearest dollar at some steps, there could be a slight inaccuracy due to the rounding.) Shouldn't the form have us do this exact calculation?
