Looking Back Can Cost You

A few weeks ago, I was part of a trail ride for my son’s mountain bike team. I was near the front of the group, and every so often I glanced back over my shoulder to check that everyone was still with us and staying on the trail.  

On one of those glances back, I clipped a fallen tree that was lying slightly into the trail, something I would have easily seen if I’d been looking where I was actually going. For half a second, I thought I was headed over the handlebars. I grabbed a standing tree on the way down and managed to stay upright, and while I initially laughed it off with those who saw it, admittedly, it rattled me for a bit.  

Nothing was wrong with checking on my team. That’s part of leading a group. The problem was that I didn’t know what was on the ground in front of me while I was doing it. Have you ever made a call that felt obviously right in the moment, only to realize later you weren’t looking at the whole picture?  

This is where financial planning comes in, or at least where it came to mind a few days later, when I read about something called the Social Security retroactive lump sum benefit.  

The Six-Month Lump Sum 

If you wait until your full retirement age or later to file for Social Security, you’re allowed to request up to six months of retroactive benefits as a single lump-sum payment when you finally do file. On paper, it sounds like a bonus: six months of benefits handed to you all at once.  

A lump sum naturally gets people’s attention. If you call the Social Security office and they ask you about this option, you may assume, based on how it’s described, that it is free money: six months of benefits you hadn’t collected yet, just sitting there waiting to be claimed.  

Here’s what’s not always spelled out: taking that lump sum resets your filing date. Social Security treats you as though you’ve started your benefit six months earlier. Since your monthly amount is tied to how long you waited to file, filing “six months earlier” on paper means a smaller check every month for the rest of your life.  

You’re not getting six months of benefits for free. You’re trading a smaller amount every month, for as long as you live, for one bigger payment today.  

What That Looks Like in Dollars 

Let’s use the top of the range, since it’s the scenario I get asked about most by clients who spent a career maximizing their earnings. To collect the maximum possible Social Security benefit, you need 35 years of earnings at or above the Social Security wage base. For 2026, that maximum monthly Social Security benefit at full retirement age is $4,152. (That number moves every year with the cost-of-living adjustment.) 

Say your full retirement age is 67 and you wait until 67 and six months to file. File normally at that point, and those extra six months earn you delayed retirement credits, roughly a 4% bump over your full retirement age benefit. Once all six months of credits are reflected, that puts the maximum benefit at about $4,318 a month.  

Take the retroactive lump sum instead, and Social Security treats you as though you filed right at 67. You’d walk away with about $24,912 up front (six months at $4,152), but your ongoing benefit drops back to $4,152 a month: about $166 less than the $4,318 you’d otherwise be getting.  

Morgan Housel spends much of The Psychology of Money making the case that money decisions are driven more by psychology than math. This is a good example of it. A $24,912 check feels like a windfall in a way a $166 monthly difference never will, even though the smaller monthly difference may eventually add up to more.  

Using this simplified example, the nominal break-even point is 150 months, or 12.5 years. That ratio is the same regardless of the initial benefit amount, but real life is messier. Cost-of-living adjustments, taxes, investment returns, the time value of money, and a spouse’s potential survivor benefit can all affect the decision. What matters is your own time horizon and what else that money could do for you.  

What This Means for You 

Someone in excellent health with strong family longevity may place more value on the higher lifetime benefit. Someone with a clear and immediate use for the money, such as paying down debt or funding a specific need, may reasonably value the lump sum more. A spouse’s potential survivor benefit, taxes, Medicare status, and the intended use of the money should also be part of the decision. It needs to be a choice made on purpose, not one backed into because a headline made it sound like free money. 

There can also be Medicare and Health Savings Account consequences. Medicare Part A coverage can be retroactive, and you cannot make HSA contributions for months in which you are covered by Medicare. Anyone still contributing to an HSA should review the timing carefully before accepting retroactive benefits.  

What would you actually do with that lump sum if you took it? That question tells you more about the right choice than any break-even calculation.  

The Bottom Line 

My job with a client isn’t to tell them whether to take the lump sum. It’s to make sure they can see the whole trail in front of them before they look back.  

Schedule an introductory phone call with Mark at this link: Mark Brinser – Introductory Phone Call

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