Thousands of retired federal, state and local government workers can escape a substantial, lifetime cutback in dependent social security benefits due them if they act quickly. By going through some basic paperwork before the end of this month, the retirees could save themselves anywhere from $100 to $500 a month for life.

What they must do if to file applications for either the dependent benefit (if their spouse is still living) or for a widow or swidower benefit due them because of a spouse who worked and earned credit under social security.

Retirees whose spouses are still living must be 62 or older to file. Those who are widowed must be at least 60. In the case of retiree filing for a dependent benefit from a living spouse, the spouse must, of course, already have qualified himself or herself for social security benefits.

The crunch comes because the Senate has approved legislation that would reduce dependent benefits from social security for anybody applying for them in the future if that person is himself (or herself) drawing a public pension.

That so-called "offset" provision is not in the House-passed social security financing bill. Senate-House conferees will meet on it early next month, and should have a compromise ironed out in time for the President to sign it in December.

If the Senate prevails, that is if the "offset" provision is retained in the bill, it would cut off part of a dependent or widow's benefit due anybody filing for it next month based on the spouse's social security.

Offset means that an individual's "dependent" or widow's benefit from a spouse's social security would be reduced on a dollar-for-dollar formula, based on how much the "dependent" gets from his or her federal, state or local government annuity.

Persons who have already filed for the dependent or widows benefit, and those already drawing it will not be affected by the offset provision if the Senate version of the bill becomes law. Persons filing for it too late will, however, be hit by the offset.

Senate estimates are that about 85,000 persons would be affected by the offset provision in the first year it became law.Many of them can't do anything because they don't meet the age 60 or 62 minimum for filing for widow's or dependent benefits. Those who do meet that age requirement - and there are thousands of them - can "save" their entire dependent social security benefit by filing now.

The explanation of the cutoff date comes from the Senate Finance Committee report (Page 28). It reads like this:

"Effective Date - The provision would become effective with respect to benefits payable for months starting with the month of enactment on the basis of applications filed in or after the month of enactment."

Retirees who think they qualify by virtue of age and a spouse with social security benefits should go to their local social security office before the end of November and apply for benefits. That will "cover" them if the bill becomes law next month. If it doesn't, or is modified, they can withdraw their applications, but they must act quickly this month to be eligible to protect their benefit.