Recently, an actuary for a major insurance company reached out to me to run a Social Security analysis. He'd been calculating lifespans for three decades and was now focused on his own.

Mark was 63, and his wife, Susan, recently turned 61. Both retired from long careers a few months earlier with no wages or self-employment income. Their teenage daughter, Lily, a 15-year-old cheerleader, had just begun her first year of high school.

Mark had studied the Social Security Administration (SSA) website and pored over his Social Security estimates with the mindset of a cautious actuary.

He said, "Ray, everything points to both of us using our savings to bridge the next seven years and waiting until age 70 to file. What do you think?"

In our Zoom meeting, I said, "If it was just you and Susan, I'd tend to agree. But let's run the numbers, because I believe Lily might bring some cheer to your household income."

Lily could qualify for a benefit on Mark's earnings record once he claims Social Security.

I gave Mark a quick summary of the SSA's rules: "Eligible children of a worker entitled to retirement benefits can generally receive payments while unmarried and under 18, with continuation for qualifying full-time elementary or secondary students, until 19."

(Different rules can extend eligibility for a disability that began before age 22, but Lily does not have a disability.)

Mark responded, "But, Ray, by the time I turn 70, Lily will be 22. She won't be eligible."

I then walked Mark through a very familiar subject: Math. Many times, in my practice, the person without a retirement statement can change the math.

A child can put a deadline on the calculation

Lily's math was simple. Her benefit was based on half of Mark's $3,200 full retirement age benefit: $1,600 a month. Over 36 months, that would add up to $57,600 before applying the family maximum.

There was more math to consider. Susan could collect a child-in-care spousal benefit while Lily was under 16, even before Susan turned 62. That would add about $800 a month to the family's income until Lily turned 16.

Using a $5,600 family maximum for our example, Mark would receive $2,400 starting on his 63rd birthday. Susan and Lily would each receive $1,200. That put the family total at $4,800 a month.

Mark responded, "Ray, even with a maximum, your new math beats mine every day. I didn't even think my daughter factored into my retirement decision."

One filing decision can affect three people.

Susan has two different interests in this decision

Mark's wife, Susan, needs to understand spousal benefits while Mark is alive and survivor benefits if he dies first.

A regular spousal benefit can be up to 50% of Mark's Social Security full retirement age (FRA) amount, with reductions for early claiming and other eligibility rules.

Mark's previous plan to wait until 70 doesn't increase that 50% base. Nor would Susan earn delayed retirement credits on a spousal benefit by waiting beyond her own full retirement age.

Susan's own retirement benefit, if she has one, is a separate calculation. SSA coordinates the benefits; it doesn't simply add two full checks together. Assuming both spouses should wait until 70 skips these distinctions.

Survivor benefits work differently. Delayed retirement credits earned by Mark can increase Susan's eventual widow's benefit. That can make delaying the higher earner valuable protection for a younger spouse.

Susan could receive up to 100% of the applicable survivor amount at her full retirement age for survivor benefits, subject to the rules. But her own retirement payment and the survivor payment aren't added together.

When one spouse dies, a household often loses one Social Security check. Unfortunately, the roof doesn't become 50% smaller. The property tax doesn't observe a mourning period.

The question for Susan is how much income she would have after Mark's death and how much she would still need.

Earlier payments change later income

Lily's potential benefits don't settle the case for claiming immediately.

For someone with a full retirement age of 67 (the FRA for those born in 1960 or later), starting at exactly 63 reduces the worker's benefit by 25%. Mark's illustrative $3,200 would become $2,400, before later adjustments. That lower starting benefit matters long after Lily's payments end. Early claiming can also affect Susan's eventual survivor income.

Parents who are still working have another issue to check: Their earnings can cause benefits for themselves and family members to be withheld.

The comparison therefore needs a household timeline. Model the years while Lily qualifies, the years after her benefits end and the years Susan might spend as a widow. Test a long life for each spouse.

Compare Mark claiming now, at full retirement age and at 70. Coordinate Susan's available benefits with each alternative. Count the savings used during any delay, along with the larger retirement and survivor payments that waiting might produce.

Ask who belongs in the analysis

Your household might have no teenagers. A former spouse, an adult child with a disability or a spouse with a very different earnings history can still change the answer.

Before filing, identify everyone who could qualify on the relevant work records, the dates their eligibility begins or ends and the income the household would retain after a death.

Mark can then decide whether the later increase is worth the payments his family would pass up now. He will be comparing actual alternatives instead of choosing the biggest number on one statement.

The Social Security application might have Mark's name at the top, but Susan and Lily still belong in the calculation.

Related Content

• Social Security Family Maximum Benefits: Are You Eligible and How Much Can You Receive?
• When Should You Start Social Security Benefits? It Depends
• 9 Changes Coming to Social Security in 2027
• When the Biggest Social Security Check Is Not the Best Choice
• Are You Much Older Than Your Spouse? Sorry, But Your Social Security Decision Isn't About You

This article was written by and presents the views of our contributing adviser, not the Kiplinger editorial staff. You can check adviser records with the SEC or with FINRA.