$ 14,160 of earned income is the allowable maxium before you start reducing benefits in 2009; (if you don't reach full retirement age of 66 within 09). Beyond that limit each $ 2 earned, costs you $ 1 in benefit reduction.
The above numbers are based on "earned income", no investment income. So one that is self employed in a business can skirt the issue nicely. Dividends rec'd from an S-Corp do not reduce your benefits. Also, one could earn monies in a C-Corp, and not take any distributions beyond the 14K, and allow other profits to accumulate for a few years. Then once you turn 66, you can earn all you want w/o reduction of benefits... so then begin taking the accumulated C-Corp earnings.
OR, if your wife is younger than you by 3 or 4 yrs, your S-Corp could pay her the excess earned income, you take the 14K in earned income to keep you under the limit, and then receive the balance as a dividend, which has no effect on reducing benefits.
Of course, never take tax advice from someone named SportsNut; always consult your personal tax advisor.
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According to SSA:
How much can you earn and still get benefits?
If you were born January 2, 1943, through January 1, 1955, then your full retirement age for retirement insurance benefits is 66.
If you work and are full retirement age or older, you may keep all of your benefits, no matter how much you earn. If you are younger than full retirement age, there is a limit to how much you can earn and still receive full Social Security benefits. If you are younger than full retirement age during all of 2009, we must deduct $1 from your benefits for each $2 you earned above $14,160.
If you reach full retirement age during 2009, we must deduct $1 from your benefits for each $3 you earn above $37,680 until the month you reach full retirement age.
Full Q & A (from the SSA website)