Name a new survivor or change the election you made at retirement

Under certain conditions, you can name a new survivor or change the election you made at retirement if you file a new election by writing OPM no later than 30 days after the date of your first regular monthly payment.

Provide or increase a survivor benefit for the spouse you were married to at retirement

If you were married at retirement and either did not provide or elected less than the full survivor annuity for your spouse, you may, within 18 months after retirement, elect an annuity reduction to provide or increase the survivor benefit if you are still married to the same person. By law, you also must pay a deposit equal to the amount by which your annuity would have been reduced had the election been made at retirement plus an amount equal to 24.5 percent of the increase in the base designated for the survivor annuity. Interest is charged on the deposit.

Provide a survivor annuity benefit for a spouse you marry after retirement

If your annuity began on or after May 7, 1985, or if you marry on or after February 27, 1986 (regardless of the date on which your annuity began), you may elect to provide a survivor annuity for a spouse you marry after retirement as described below. If you make this election, your monthly annuity will be reduced.  The Office of Personnel Management (OPM) will send you detailed information about your reduced annuity when you notify them you want to make this election.

If you were unmarried at retirement and married afterward, you must notify OPM in writing within two years after the marriage if you want to provide a survivor annuity benefit. The reduction in your annuity begins no earlier than the first of the month beginning 9 months after the marriage date.

If you were married at retirement, experience the end of the marriage (through death, divorce, or annulment), and marry again, you must notify OPM in writing within two years after the marriage if you want to elect a reduction in your annuity to provide a survivor annuity for your new spouse. The reduction in your annuity begins no earlier than 9 months after the marriage date.

Source:  OPM RI 20-59