According the IRS website, self employment income above $89.7k isn’t subject to social security tax.
Does that same limit apply if your non-self employment income and self-employment income exceed $87.9k?
In other words, if you make $100k at a “regular” job and another $30k in self-employment, how much of the $30k is subject to self-employment social security tax?
Based on the instructions for Schedule SE, it sure looks like you’d have to pay social security tax on any self employment income up to $87.9k, regardless of your other income.
What ever you figure you own in Schedule SE you put on line 57 of your 1040, this is the self-employment SS tax you owe. It will be double what you would pay as an employee because YOU are the employer matching the employee’s SS. But you also get to deduct half of that number from your AGI on line 30 of your 1040. So you don’t have to pay income tax on the 50 percent premium of SS taxes you owe.
Later on, on line 66 of your 1040 will be able to make an adjustment to the amount reported on line 57. That is, if line 30 (50 percent of your self-employment SS tax) plus the amount of SS you paid in as a regular employee is over $5,449.80, you will put the difference (excess) here on line 66. That way, your “employee” SS payment is limited to $5.449.80.
So, the bottom line is this, the MAXIMUM SS you will pay is $5.449.80 plus 50 percent of the SS you figured on Schedule SE.
I believe this is correct, other tax people please chime in.