Before Mom Moves $500,000 Into 5% CDs at 68, Someone Should Show Her the Social Security Tax Worksheet

Imagine a 68-year-old widow with $500,000 in a savings account sees her bank advertising a 5% CD and wants to move the whole balance into it. Her family likes the idea because the interest is guaranteed and the principal can’t fall with the stock market. The caveat is that nobody has worked out how $25,000 a year in new interest will add to her Social Security checks, or how much of the 5% she will keep after taxes.

The truth is that far too many retirees face this exact decision. On Suze Orman’s podcast, a newly retired 70-year-old with $300K in excess cash asked whether she should simply open a CD. The question sounds simple, but the tax answer is far more involved.

How $25,000 of Interest Rewrites Her Tax Return

Federal law determines whether the IRS taxes Social Security using what it calls provisional income. That figure is half your benefits plus all your other income, including tax-exempt interest. For single filers, benefits become taxable once provisional income exceeds $25,000. Above $34,000, up to 85% of benefits can be taxed (26 U.S.C. § 86(a)(2)). Neither threshold has ever been adjusted for inflation.

For example, suppose Mom receives the average retired-worker benefit of $2,170 a month after the 2027 COLA, or $26,040 a year. She also takes $15,000 a year from an IRA. That puts her provisional income at $28,020, so only $1,510 of her benefits are taxable. Add the CD interest, and provisional income rises to $53,020, while taxable benefits jump to $20,667.

Why the 85% Zone Matters More Than the Rate

In that range, each extra dollar of interest also makes 85 cents of Social Security taxable. Even after the $16,100 standard deduction and the new $6,000 senior deduction, her taxable income comes to about $38,567. That sits inside the 12% bracket. Because each dollar of interest is taxed as $1.85 of income, her real tax rate on the CD interest is about 22%.

At that rate, a 5% CD pays her about 4% after tax. CPI-W, the inflation index the government uses to set Social Security raises, was up 4% from a year earlier. After taxes and inflation, her purchasing power remains about the same.

Checking Whether 5% Is Even the Real Offer

The national average 12-month CD rate is somewhere around 2%, and the top of the Federal Reserve’s target range is 4%. A 5-year Treasury yields 5%. A 5% CD is probably either a long-term lockup or a promotional rate that may not renew at the same level. On top of that, $500,000 exceeds the FDIC insurance limit for one depositor at one bank, so she would need several banks or different account ownership types to keep it all insured.

Two Ways to Deploy the $500,000

Path One: All of It in Taxable CDs

Path One is undoubtedly the simplest option, as every dollar is guaranteed, and none of it moves with the stock market. The downside is that it produces the most taxable income possible, puts her into the 85% zone every year, and locks in a fixed nominal return while her expenses keep rising. People often move tax-exempt municipal bonds into this role, but that doesn’t fix the problem. Muni interest still counts toward provisional income, and the IRS worksheet adds it back on line D. For most retirees whose Social Security is already near the thresholds, this path comes out behind.

Path Two: A Short Ladder Plus Assets That Defer Income

Under this plan, CDs or Treasuries cover the gap between her spending and her Social Security for three to five years. A ladder means the CDs mature one after another, so cash comes due each year. Treasury interest is exempt from state income tax, which helps in high-tax states. I Bonds, currently paying 4%, don’t owe federal tax on interest until they’re cashed in, although annual purchases are capped.

The remaining money goes into a diversified stock-and-bond index portfolio. Most of that portfolio’s return builds up as gains she hasn’t sold yet, and unsold gains aren’t considered toward provisional income. She chooses when to sell, so she can decide which years the income shows up.

This path carries market risk on the invested portion, but the ladder ensures she never has to sell in a downturn to pay her bills.

What to Run Before Signing Anything

Start by filling in the Social Security Benefits Worksheet in the Form 1040 instructions twice: once with the CD interest and once without it. IRS Notice 703, which comes with every Form SSA-1099, has a shorter version. If the CD interest moves her above $34,000 of provisional income, the advertised 5% is the wrong number to compare against other options.

Second, CDs work best for money she needs on a set date, and putting the entire $500,000 into CDs in a taxable account is likely the costliest way to get safety. If she also has an IRA that will face required minimum distributions later, planning her withdrawal order with a fee-only advisor matters because the IRA withdrawals and the CD interest both count toward the same Social Security thresholds.

Contact [email protected] for any questions or corrections.