I wonder, if I switched jobs mid-year, how does the second employer know when I have reached my taxable limit?

I've read that if you have more than one job and your total is more than the SS limit you need to watch your statements very closely so they don't take more out than the total limit. Supposedly you would need to contact some government agency and get a refund for the amount overpaid.

I guess anyone in that situation could do a Google search for the agency who would handle this.