Spousal Social Security will pay you a monthly check during retirement, even if you never worked for pay in your life. The only eligibility requirement is being married to a qualifying worker or having been married to one for at least 10 years before divorcing.

But those hoping to maximize their Social Security benefits will need to do a little more. Here are three things everyone eligible for spousal Social Security should know before applying.

Mature couple getting married.

Image source: Getty Images.

1. How the government calculates spousal benefits

Spousal Social Security benefits are based on the qualifying worker's primary insurance amount (PIA). This is the benefit the worker is entitled to when they reach their full retirement age (FRA), which is between 66 and 67, depending on their birth year.

The maximum spousal Social Security benefit is half the worker's PIA. So if the worker qualifies for a $2,000 PIA, their spouse could receive up to $1,000 per month.

It's possible to estimate your spousal benefit by first determining your partner's PIA. You can do this by having them create a my Social Security account. There, they can view estimates of their Social Security checks at every claiming age. There's also a tool where they can estimate your spousal benefit by entering your date of birth and the age when you plan to claim.

2. How your claiming age affects your benefit

You may already know that if a retired worker claims Social Security before they reach their FRA, their monthly checks will be reduced. They can also delay Social Security until age 70. In that case, their checks will continue increasing slightly every month. Their choices won't affect your spousal benefits at all, but your choices will.

Claiming before you reach FRA will reduce your checks by 25/36 of 1% per month for up to 36 months of early claiming. If you apply more than 36 months before your FRA, you'll lose an additional 5/12 of 1% per month. For the majority of workers with an FRA of 67, that means you'd shrink your checks by 35% by claiming immediately at 62.

But early claiming is occasionally the right move. Those with serious health issues or lacking other sources of retirement income could benefit more from claiming early than they would from delaying Social Security. But for most workers who can afford to do it, delaying retirement checks will result in a larger lifetime benefit.

There's no reason to delay spousal benefits past your FRA, though. Spouses can't qualify for delayed retirement credits like workers can, so waiting longer than their FRA will only cost them money.

3. When you can apply

Those currently married to a qualifying worker can't claim a spousal benefit until the worker applies for retirement benefits themself. Divorced people hoping to claim an ex-spousal benefit may do so even if their ex hasn't signed up yet, but they must have been divorced for at least two years if their ex isn't currently claiming.

Because of this limitation, married couples need to coordinate their claiming strategy. It might make sense for the retired worker to claim a bit earlier than they otherwise would have if waiting is costing their partner their spousal benefit.

If both partners qualify for retirement benefits and spousal benefits, things are a little trickier. When both have earned similar amounts over their careers, it's often better for both people to delay as long as possible, barring health or financial constraints.

But when one spouse has significantly out-earned the other, it can be advantageous to have the lower earner claim their own retirement benefit early, possibly right away at 62. This extra money could help the higher earner delay Social Security until they qualify for larger checks. Then, when they sign up, the Social Security Administration will automatically switch the lower-earning spouse over to a spousal benefit if it's worth more than what they're currently receiving.

It's good practice to have Social Security claiming ages picked out, even if you're decades away from retirement. Just be prepared to adjust your strategy over time, as needed. And make sure to stay on the same page with your spouse and have a plan for how you'll cover the expenses that Social Security won't.