A New $6,000 Senior Deduction Starts Phasing Out at $75,000 of Income — and One Roth Conversion Can Erase It

A 66-year-old retiree finds herself $480 below a tax cutoff and is following the usual advice from her financial adviser. The tax rate she was told to expect turns out to be inaccurate, and she would not have realized it until tax-filing season.

Last year, Congress created a new tax break for people age 65 and older, but it came with a hidden catch that many celebratory write-ups left out. The deduction can be worth as much as $6,000 per person for tax years 2025 through 2028. Once income rises above $75,000 for single filers or $150,000 for joint filers, the benefit begins to phase out quickly: 6 cents for every dollar over the limit. It disappears entirely at $175,000 for single filers or $250,000 for couples.

That matters because one of the most common retirement moves for people in their 60s is to convert part of a traditional IRA to a Roth IRA. But that conversion counts as income in the year it happens. Make a large enough conversion, and you can accidentally lose the deduction you were expecting, with the surprise showing up only when the tax bill is due.

Here is what that looks like for a retiree who seems to be doing everything correctly.

A retiree hovering just below the threshold

She is 66, single, and retired last year. Her income includes a $28,000 pension, $20,000 a year withdrawn from a traditional IRA, and $2,600 a month in Social Security benefits, or $31,200 a year.

The IRS taxes Social Security on a sliding scale. When her other income is combined with half her benefit, the total comes to $63,600, well above the point where up to 85% of Social Security becomes taxable. In her case, the full 85% applies, so $26,520 of her benefits count as income.

That leaves her adjusted gross income at $74,520. Compared with the $75,000 phaseout point, she is only $480 under. She receives the full $6,000 senior deduction, and combined with the $16,100 standard deduction and the additional $2,050 for being over 65, she reduces her income by $24,150 before the IRS applies tax. Her taxable income is $50,370, almost exactly at the top of the 12% bracket. Her federal tax bill is about $5,800.

She has done nothing wrong. She is also standing at the edge of two cliffs at the same time.

What happens with a $40,000 conversion

Her adviser recommends converting $40,000 from the traditional IRA to a Roth this year, which is standard advice for someone her age with a healthy balance and a long time horizon. The idea is simple: pay tax now at a known rate, then let the money grow tax-free and avoid required withdrawals at age 73.

That $40,000 is added to her $74,520 of income, raising her adjusted gross income to $114,520. Three things happen at once.

First, the conversion itself is taxable. Since she was already at the top of the 12% bracket, every dollar of it is taxed at 22%. That comes to $8,800, which she expected.

Second, the senior deduction shrinks. She is now $39,520 above the $75,000 line, and 6% of that equals $2,371. Her $6,000 deduction falls to $3,629. The lost $2,371 is then taxed at 22%, adding another $522 she did not anticipate.

Third, her Social Security does not change, but only because she was already at the 85% maximum. A retiree with less outside income would also see more of her benefits become taxable, which is the more familiar trap.

In total, the $40,000 conversion costs about $9,320, for an effective rate of 23.3%, before any state taxes. That may still be worthwhile if she expects to be in the 22% or 24% bracket later. The point is that the 22% figure she was given was wrong, and she would not have known it until filing.

What happens with a $100,000 conversion

Now imagine she goes bigger, the way some people do after hearing that today’s tax brackets may not last or that they should fill the 22% bracket while they still can.

A $100,000 conversion pushes her adjusted gross income to $174,520. She is $99,520 over the limit, so 6% of that amount, or $5,971, is lost from the deduction. In effect, the senior deduction is reduced to just $29. The lost $5,971 deductibility costs her roughly $1,400, and the top $50,000 of her taxable income has already spilled into the 24% bracket. Her total federal tax for the year rises to about $30,000, compared with roughly $5,800 otherwise.

She would also receive a Medicare notice two years later. Medicare bases income-related premium surcharges on a tax return from two years earlier, and the first surcharge tier for a single filer in 2026 begins at $109,000 of income. Her $174,520 places her three tiers higher, adding more than $300 a month to her Part B and Part D premiums throughout 2028.

The number worth remembering

If you are 65 or older and your income is close to $75,000 as a single filer or $150,000 as a married couple filing jointly, the Roth-conversion calculation now includes a new line for the next three years. Every dollar converted above the threshold costs 6 cents of deduction, which at the 22% rate works out to about 1.3 cents of extra tax per dollar converted, in addition to the tax on the conversion itself. It is not huge, but it adds up, and it is easy to miss unless you specifically look for it.

For a couple in which both spouses are 65 or older, the deduction is $12,000 and the squeeze is twice as large: 12 cents of lost deduction for every dollar over $150,000.

A cleaner approach, and one many advisers are now using, is to convert only up to the threshold and stop there. For the retiree above, that would mean converting about $480 this year, which is hardly worthwhile, so she faces a real decision: accept the extra cost because her future tax rate will be higher, or wait until 2029, when the senior deduction expires and the phaseout disappears with it.

There is another option for people who have cash outside the IRA. They can pay the conversion tax from a taxable account, keep IRA withdrawals to the minimum, and let pension income and Social Security cover the year. That keeps income near the cutoff, preserves the deduction, and still funds the Roth.

The takeaway

The $6,000 senior deduction is real money for four tax years, worth about $1,320 a year to someone in the 22% bracket. It is also easy to lose by accident, because the very move many retirees are encouraged to make can wipe it out. Before converting anything to a Roth between now and 2028, add the conversion to your income and see where you land relative to $75,000 or $150,000. If you are above the line, the true cost of the conversion is higher than the bracket rate you were quoted.