Let's say you have one job that during the year pays 204k. The social security cap is 102k, so by the end of June your net salary paid from the start of the year is 102k, and from July to December you pay no social security tax, and neither does your employer. Is this right? So the net social security tax paid for the year is 12648, which is reasonable.
Now let's say you have two jobs that each pay 102k a year. By the end of June is job has paid you 51k, which is below the 102k limit, so they continue to withhold social security till December. As a result, the taxpayer wlil have paid 12648 (6324 from each company) by the end of the year and they can get a refund of 6324 for excess social security tax paid. However, each company pays 6324. So the net social security tax paid by the end of the year is 6324 (employee's portion after claiming excess social security) + 6324 + 6324 -= 18972.
My reason for asking is that if the second company is your own S Corp from which you draw a W2 salary, then you could end up paying more social security tax.
By contrast, if your company was a sole proprietorship, then all your earnings would be on Schedule C. Then Schedule SE will compute the social security tax as zero as follows:
Line 6: Net earnings from self employment = 102000*0.9235 Line 7: Maximum amount subject to SS = 102000
Line 8a for 2008 will read
Total social security wages and tips (total of boxes 3 and 7 on Form(s) W-2) and railroad retirement (tier 1) compensation. If $102,000 or more, skip lines 8b through 10, and go to line 11
So Line 10, social security tax is zero. And if your W2 income from the first job was less than 102k, say 100k, then only 2k of your self- employment income would be subject to social security tax.
Line 11: Medicare = Line6*0.029 = 2731.71
So what's the solution to avoid paying too much social security tax?