The Fed Just Raised Its Inflation Forecast. For One Retired Couple, a Bigger Social Security Bump Could Mean a Bigger Tax Bill

A married couple in their early 70s, living mostly on Social Security with modest withdrawals from a traditional IRA, just heard news that should feel good. On June 17, 2026, the Federal Open Market Committee (FOMC) left the federal funds rate unchanged at 3.5% to 3.75% and dropped its prior easing bias, a hawkish turn under new Fed Chair Kevin Warsh, who succeeded Jerome Powell. The committee’s updated Summary of Economic Projections now pencils headline inflation around 3.6% by year-end 2026, up from estimates of 2.7% in March, with core around 3.3%. Nine out of 18 Fed policymakers project another rate hike later this year.

For retirees, hotter inflation tends to push the next Social Security cost-of-living adjustment (COLA) higher. A bigger raise sounds welcome. The catch is that the rules that decide how much of that raise gets taxed have not budged in over four decades, and a similar quirk affects Medicare premiums for higher-income retirees. One contributor on a retirement forum recently put it well: bigger COLA is a raise the IRS takes a bite out of before you ever see it.

Why a Bigger COLA Can Mean a Bigger Tax Bill

Social Security’s annual adjustment is driven by CPI-W, the Consumer Price Index for Urban Wage Earners, using the third quarter average compared with the prior year, a formula that sits outside the Fed’s control. The Fed’s preferred gauge is core PCE, a different index with different weights. The Fed’s raised inflation outlook is a signal about the environment around the COLA formula. A hotter-inflation backdrop generally tends to produce a larger COLA, but the exact number is decided by the summer CPI-W readings.

Here is where the math turns against retirees. The IRS uses something called provisional income to decide how much of a Social Security check is taxable. It equals adjusted gross income (AGI), plus tax-exempt interest, plus half of Social Security benefits. For a married couple filing jointly, provisional income above $32,000 makes up to 50% of benefits taxable, and above $44,000 makes up to 85% taxable. Those thresholds have been frozen since 1984 and are not indexed to inflation.

That “up to 85%” refers to the share of the benefit exposed to ordinary tax rather than the tax rate itself. The point is that every COLA nudges more of the benefit across those frozen lines. Real buying power may not improve at all, yet a larger slice of the check shows up on the tax return. This is the so-called tax torpedo, and it hits hardest at modest middle-income households where small income changes can flip a big chunk of benefits from untaxed to taxed.

How It Connects to IRA Withdrawals and Medicare

For this couple, the IRA is the lever they actually control. Every dollar pulled from a traditional IRA lands in AGI, which feeds straight into the provisional-income calculation. A larger required minimum distribution (RMD) in a high-COLA year can stack on top of the raise and push more benefits over the 85% line.

The same rising income can brush against Medicare’s Income-Related Monthly Adjustment Amount, or IRMAA, which adds a surcharge to Part B and Part D premiums. For 2026, the first IRMAA tier kicks in above $109,000 for single filers and $218,000 for joint filers, based on modified adjusted gross income (MAGI). IRMAA works as a cliff rather than a phase-in, so a single dollar over a threshold can mean a full surcharge for the year.

What This Couple Can Actually Control

A few things are worth thinking through before the next tax year closes:

1. Sequence withdrawals deliberately. If some retirement savings sit in a Roth, drawing from there in high-COLA years can keep provisional income from drifting across a threshold, because Roth withdrawals do not count toward AGI.
2. Watch the IRMAA cliffs two years out. Medicare uses a tax return from two years prior, so a Roth conversion or large capital gain today can raise premiums later. A tax professional who understands retirement sequencing is often worth the fee.

The frozen thresholds are a policy quirk that retirees inherited. The couple cannot change the formula, but they can shape what lands in AGI each year, and that is usually where the real money is saved. Every household’s mix of accounts and income is a little different, so the right move for one retiree can be the wrong one for the neighbor down the street.