(MONEY Magazine) – • WHAT IT IS That statement Social Security sends you three months before your birthday estimating your future monthly retirement benefit

• WHY YOU SHOULD LOOK TWICE Harvard law professor Howell Jackson says these statements can be misleading. The projections of monthly payouts are in today's dollars, not inflation-indexed, and they assume you'll work to 62 at the same salary with no time off. If that's unlikely, go to ssa.gov/planners/calculators.htm to calculate adjustments. Also, Jackson suggests multiplying the monthly benefit by 12 (as in months) to gauge what percentage of your annual income Social Security will replace.

• ERROR ALERT Since benefits are determined by how much you pay into the system, make sure your earnings history is right by comparing it to W-2s, particularly in years you switched jobs. Mistake? Call the 800 number pronto.

• DISCLAIMER It's no secret that Social Security faces a funding crunch and may pay out less than it promises--a fact that your statement points out, in bold, just below your estimated benefit. Anyone 55 or older will likely be safe from changes. Younger workers: Take it to heart.

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