Millions of people other than retirees claim Social Security benefits, and spouses of retirees who don’t qualify on their own are one of these cohorts. In fact, nearly 1.9 million people claimed Social Security through the spousal benefit in September of this year. The average monthly check size was about $909, which comes out to about $10,908 annually.

The Social Security program can be complex. That’s why all retired couples should carve out some time each year to examine the spousal benefit, to see if one of them qualifies and if it’s a good option based on their specific situation. Here are three things retired couples should know.

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1. Who qualifies, and for how much?

The purpose of the spousal benefit is to provide benefits for someone who doesn’t qualify for Social Security benefits as a retiree. Workers with 40 work credits, the equivalent of working for at least 10 years, qualify for Social Security benefits. The spousal benefit becomes an option when someone is married to someone who fully qualifies and has already filed for benefits.

Spouses must be 62 years old, although they can be younger if they have a child younger than 16 or with a disability and are owed benefits on the spouse’s record.

Spouses who claim benefits early will see their benefits reduced, similar to what happens with full retirees. Claiming spousal benefits at 62 can lower benefits to 32.5% of the full amount the spouse’s partner might be entitled to if they retire at their full retirement age (FRA), which is 67 for people born in 1960 or later. The Social Security Administration (SSA) lowers spousal benefits by 25/36 of 1% for every month before the FRA. However, if the number of months is more than 36, benefits are further lowered by 5/12 of 1% monthly. Spouses who retire at their FRA could receive as much as half of their partner’s benefit amount at their FRA.

2. The spousal benefit may come into play even if you have a full work history

Workers who earn 40 Social Security credits and qualify as retirees on their own may also reap the benefits of the spousal benefit if it is higher than their own. If you are eligible for both benefits, you only have to apply once thanks to “deemed filing.”

First, the SSA will pay out your retirement benefit. If your spousal benefit happens to be higher, the SSA will bridge the gap so your benefit is the higher of the two. For instance, let’s say your monthly benefit is $750 and your spousal benefit is $1,000. The SSA will first pay the $750 of your retirement benefits and then add $250 so your benefit is equal to the higher of the two options.

3. Divorce can be a dealbreaker

A spouse can qualify for the spousal benefit if they’ve been married to their partner for just one year. However, if you divorced your partner, you would only qualify for the spousal benefit if you were married for at least a decade.

A person can also only qualify for a spousal benefit of a divorced partner if they remain unmarried. Otherwise, they would likely qualify for benefits through their new partner. A spouse can still take advantage of the spousal benefit even if their former partner remarries.

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