Foreign Service officers who are divorced next year may have to split their monthly retirement checks for life with their to-be-former spouses.

The new Foreign Service Act that Congress approved before it recessed contains a precedent-setting pension-sharing provision that could -- in time -- affect all federal and postal employes and military personnel.

Language in the act, proposed by Rep. Patricia Schroeder (D-Colo), sets out federal guidelines that courts must consider when making divorce settlements. The legislation goes into effect Feb. 15, assuming President Carter signs the act into law. He is expected to sign it.

Under the Schroeder plan's formula, anyone married to a foreign service officer (man or woman) for 10 years or more is entitled to a prorata share of the FSO's annuity, subject to approval by the court. It does not automatically provide for a divided pension, but it does for the first time require courts to consider such an option. It does not affect individuals already divorced or those divorces become final before Feb. 15, 1981.

If the court approved, an individual married to a FS officer for the entire length of his or her career could be entitled to up to half the employe's annuity. The State Department would issue or authorize two monthly checks, one to the retiree and one to the spouse. Persons married to an employe for 10 years of a 30-year career, under the formula, would be entitled to one-sixth of the annuity. The former spouse also would receive regular cost-of-living adjustments.

Schroeder introduced similar legislation covering federal workers and military personnel, but the plan died in Congress. She will introduce it again next year.

An official familiar with the legislation said its pendiing adoption has had the effect of pushing some foreign service officers into making quick divorce settlements, and of causing some of their spouses to "hang in there" with their marriages until the new law is on the books.

The number of the bill is H.R. 6790.