The earnings record is the document, and the estimates are a consequence of it. Every Social Security benefit is computed from the individual's own history of covered earnings. Wages reported by an employer and self-employment income reported on a return are posted to the record under the person's number, and everything downstream follows from what is posted. That makes the earnings list the one part of the statement worth reading line by line and the one part a person can actually act on. The estimated benefit figures cannot be corrected, because they are not claims about anything that has happened; they are projections that depend on assumptions about earnings that have not occurred yet.
Who is entitled to one. Section 1320b-13(a)(3) defines an eligible individual as someone who has a Social Security account number, has attained age 25 or over, and has wages or net earnings from self-employment. A separate limb reaches an individual whose pattern of earnings indicates a likelihood of noncovered employment, which is the category the statute singles out for an additional explanation. The agency is separately directed, to the maximum extent practicable, to take the steps necessary to make eligible individuals aware that the statement is available.
What the statute requires and what happens in practice are different questions. Section 1320b-13(c)(2) directs the Commissioner to provide a statement on an annual basis to each eligible individual who is not receiving benefits and for whom a mailing address can be determined, and provides that statements to those under age 50 need not include estimates of monthly retirement benefits provided a description of the benefits available on retirement is included instead. That is the duty. Whether a paper statement arrives, and how often, is not something to plan around, and the practical course is to obtain the statement directly from the Social Security Administration rather than to wait for one. The agency provides it through its own website, and requesting it is also how the statute contemplates most people getting it.
The correction window is the most consequential rule attached to the document, and hardly anyone knows it exists. Under section 405(c) of title 42, the agency's records of wages and self-employment income for a year become conclusive after a period the statute defines as the "time limitation": three years, three months and fifteen days following that year. Before it expires the agency can correct an erroneous entry or add an omitted one straightforwardly. After it expires, the absence of an entry is conclusive evidence that no such earnings existed, unless one of a list of statutory exceptions applies.
Those exceptions are broader than the rule sounds, and two of them do most of the work. The agency may still act after the deadline to correct errors apparent on the face of the records, to delete an entry that is erroneous as a result of fraud, to conform its records to tax returns and information returns filed with the Internal Revenue Service, and to include wages paid during the year to an individual by an employer. Those last two matter a great deal in ordinary cases: an employee whose employer filed a wage report that never reached the record, or whose earnings appear on a return the Internal Revenue Service holds, is generally not shut out by the passage of time. The window is nonetheless the reason to check the record now rather than at retirement, because the evidence a correction depends on, meaning pay records, tax returns and forms, is easiest to produce while it still exists.
Two specific things to look for. A year showing zero earnings that you know you worked is the obvious one, and the usual causes are a name change that was never reported, a transposed Social Security number on a wage report, or self-employment income reported without the accompanying self-employment tax. A year showing substantially less than you earned is easier to miss and matters just as much, because the benefit formula uses the highest years of indexed earnings and a suppressed year can displace nothing or displace something, depending on where it falls in the ranking.