A Retired Couple With $40,000 of Pension Income Can Sell $50,000 of Appreciated Stock Before Dec. 31 and Pay $0 Capital Gains Tax. Convert $80,000 to a Roth the Same Year and About $24,000 of That Gain Gets Taxed at 15%

Retirees living on a small pension income can use one of the most generous breaks available: a 0% federal rate on long-term capital gains. However, when the IRS calculates your tax, gains sit on top of ordinary income, so anything that increases ordinary income, such as a Roth conversion, can push those gains into the 15% bracket. With about ten weeks left in 2026, here is how this could play out for a married couple, both 65 or older, living on $40,000 a year of pension income and holding stock with a $50,000 long-term gain.

Why $50,000 of Gains Can Cost Nothing

In 2026, married couples filing jointly pay 0% on long-term gains as long as taxable income stays at or below $98,900. Before anything counts toward that ceiling, this couple takes a standard deduction of $32,200, plus an extra $1,650 for each spouse who is 65 or older.

The One Big Beautiful Bill added a third layer: a $6,000 senior deduction for each qualifying person in tax years beginning before January 1, 2029. Together, the couple deducts $47,500 before any tax applies.

Pension plus gain totals $90,000, leaving $42,500 of taxable income. Deductions cover the full pension, so all of that taxable income is capital gain, and it all falls below the 0% ceiling, meaning the federal bill is zero. The couple still has $56,400 of room before the 15% rate kicks in.

How an $80,000 Roth Conversion Changes the Math

Money moved from a pretax retirement account to a Roth counts as gross income in the year you convert it, under 26 U.S.C. § 408A(d)(3)(A)(i). Converting $80,000 increases ordinary income to $120,000 and adjusted gross income to $170,000.

The conversion creates two problems. First, the senior deduction reduces by 6% of modified AGI above $150,000 for joint filers. Each spouse’s deduction falls to $4,800, and total deductions drop to $45,100. Second, ordinary taxable income rises to $74,900, which takes up most of the 0% space before the gain is even counted. That leaves just $24,000 of the gain under the ceiling. The remaining $26,000 is taxed at 15%, a bill of $3,900.

If you ignore the phase-out, the taxed share is $23,600. The shrinking senior deduction slightly increases the taxable amount.

What the Conversion Actually Costs

On paper, the converted dollars fall into low brackets. For joint filers in 2026, the 12% bracket runs up to $100,800, so ordinary tax comes to $8,492. Add the tax on the gain, and the total federal bill is $12,392. Without the conversion, the bill would have been zero.

Spread across the converted amount, that works out to an effective rate of about 15.5%, well above the 12% bracket the couple seems to be in. Each converted dollar pays 12% on itself and also moves a dollar of gain out of the 0% zone into the 15% zone, which planners call stacking, and you won’t see it on a bracket chart.

Where the Average Retired Couple Fits

This example excludes Social Security to keep the math clean, but most retired couples receive it. The Social Security Administration estimates that the average aged couple with both spouses receiving benefits gets $3,238 a month. That rises to $3,355 in 2027 after a 3.6% cost-of-living adjustment.

As other income rises, more of those benefits become taxable. That adds ordinary income just as a conversion does, and the 0% room reduces even further, so a couple with typical benefits should rerun every figure above with their own numbers.

Three Moves to Weigh Before Dec. 31

1. Size the conversion to fit under the 0% ceiling. In this example, a $56,400 conversion brings total income to $146,400. That stays below the phase-out threshold and lands taxable income right at the ceiling. Ordinary tax is $5,372 (an effective rate of about 9.5%), and the entire gain stays tax-free.
2. Split the two moves across tax years. Take the gain in 2026 and convert in 2027, or do it the other way around. Each year comes with its own standard deduction and a fresh 0% ceiling, so neither move has to share space with the other.
3. Model the whole return before acting. Recent CNBC coverage featured an advisor explaining when a conversion is not worth the cost. The senior deduction phase-out, Social Security taxation, and Medicare premiums all depend on the same income figure.

The 0% capital gains rate is worth real money to middle-income retirees, and a couple on $40,000 of pension income can use it on $50,000 of gains this year.

A Roth conversion and a stock sale compete for the same space under the ceiling. Whichever one takes that space first gets the cheap room, and the other one pays for it. If the couple doesn’t plan the order, doing both just because December arrived turns a $0 bill into a $12,392 one. Between the last paycheck and the first required withdrawal, retirees often see the lowest tax rate they’ll face again, which is the whole point of our free Roth conversion guide.

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