I'm 70 and have collected Social Security since age 62. Do I pay in again if I return to work? -- Mike Mobley, Sacramento, Calif.
Yes. Even though you're already collecting, you'd have to pay Social Security taxes: 6.2% of your earnings on wages up to a cutoff that will be $117,000 in 2014, says AARP's Jonathan Peterson, author of Social Security for Dummies.
Some good news: Because you are beyond your full retirement age of 66, working won't reduce your benefits. (In years before your full retirement age, benefits would be cut by $1 for every $2 you earn over an exempted amount -- $15,480 in 2014 -- although you'd get that money later as a higher benefit.)
Your new work may boost your future benefits, which are based on your top 35 years of earnings. But any bump is likely to be noticeable only if you haven't already had 35 years of earnings.