I can't leave it at that...

The basic reason for the recapture is that the 2% break is only for money earned the first two months of the year. Soc. Sec withholdings are still stopped when the taxpayer reaches the $110,000 limit. Without the recapture, high income earners would possibly gain a tax advantage over those that do not earn over $110,000/yr.

Most easily explained by:

Taxpayer #1 earns $9167/mo. Jan - Feb he pays 4.2% = $770. Mar -Dec he pays 6.2% = $5684, for a yearly total of $6454.

Taxpayer #2 earns $55000/mo. Jan and Feb he pays 4.2% = $4620. Mar - Dec he pays nothing, for a yearly total of $4620.

So, the guy making $660,000/yr would be paying $1834 less than the guy making $110,000/yr. That of course, is a worst case scenario. But, I thought it would be easiest for the dittoheads to follow.

That's the reason. If they agree to a complete year of 4.2%. The recapture will be unnecessary.