Would you like to make sure you get every penny due you from Social Security when you retire, or if you become disabled? And assure that your spouse and children will get the maximum Social Security benefits if you die?

Of course you would.The first step is to check your Social Security earnings record - now - to make sure the maximum possible earnings have been credited toward your Social Security.

The penalty for not checking could be the loss of hundreds of dollars in benefits payments later on.

To be sure, the chance of losing a really large amount of money is slim. Only 3 percent to 4 percent of people who check their records raise questions about them, according to the Social Security Administration, and not all those questions ultimately disclose errors in the agency's records.

In addition, even if a full year of earnings is missing from a record, the resulting reduction in Social Security payments would be only a few dollars a month in many cases.

That's because one basis for calculating benefits is the length of time you have paid Social Security taxes, and the longer you have paid the taxes the less benefits you would lose if just one year's records were missing.

Minimum retirement benefits are available to most people who have paid the taxes for 10 years, and maximum benefits go to those who have paid into the system for at least 35 years. The level of benefits also depends on how much you have paid in Social Security taxes during that time.

Several hypothetical scenarios tested by the Social Security Administration in Philadelphia showed losses of $1 to $8 in monthly retirement benefits if one year of earnings was dropped from a 40-year working life.

However, the shorter your working life before you begin collecting benefits, the more damage would be done by a dropped year, said Dennis Conroy, a Social Security spokesman in Philadelphia.

The penalty also would be worse for people who have wide swings in their earnings, if a high-earnings year were dropped and a low-earnings year had to be substituted in calculating benefits, Conroy said.

The substitution of a low-earnings year for a high-earnings year also could affect someone near retirement, whose dropped year probably would be near peak earnings levels. For example, the scenario that showed an $8 reduction in monthly benefits was based on the loss of a year of earnings at age 53.

While that may not sound like much, it would amount to $1,440 over 15 years.

The effect also would be worse if many years of earnings were missing from a record, as happened with a client of Philadelphia financial planner Irving Braunstein. This woman's record showed all her earnings under her married name, but didn't include the 10 years' worth of earnings under her maiden name.

The sooner such errors are reported, the easier they are to correct, Conroy said. Good taxpayer records, including W-2 forms, also make corrections easier.

But finding this kind of error is up to you. In many cases, the Social Security Administration has no way to check on its own that the information in its records is correct.

"We would like everybody to get their records, because we want people to verify that the information we have is accurate," Conroy said.

Furthermore, if you don't discover an error within a few years after it is made, you may lose your chance to have it corrected. Social Security rules give you three years, three months and 15 days after the end of each tax year to request corrections of errors made in that year. Thus, April 15 will be the deadline for making corrections to your records for earnings in 1985; records for 1988 can be corrected until April 15, 1992.

While the deadlines are waived in some cases, the easiest way to avoid trouble is to get a copy of your earnings record every three years.

In August, the Social Security Administration inaugurated both new computer software and a new earnings-report form that together give taxpayers more information. Most notably, the new system calculates the benefits you would receive based on your estimates of when you will retire and how much you will earn before retirement.

The form also shows your benefits should you become disabled, and your survivors' benefits in case you die - important because nearly a third of the 38.4 million people receiving Social Security as of June were getting either survivors' or disability benefits.

Some taxpayers who previously checked their records may be alarmed to see that the new form credits them with less income than the old form did. But in most cases it was the old form that was incorrect, says David L. Zalles, a Lafayette Hill, Pa., accountant.

Zalles explained: If a person had income from two sources, and both were taxed for Social Security purposes, the total Social Security tax paid may have exceeded the annual limit. The old earnings report would have shown the entire payment incorrectly as a Social Security credit; the new form credits only the proper amount, Zalles said.

(The excess payment needn't be lost; by filling out the proper line on your return, you can have that amount credited toward your federal income-tax payment, according to Zalles.)

Copies of the new form, which you must fill out and send to the Social Security Administration, are available by calling either 1-800-937-2000 or 1-800-234-5772. Both lines are in service 24 hours a day, seven days a week; sometimes you may reach an answering machine that will take your request. The forms also are available at any Social Security office.