A Mid-Year Tax Checkup for Retirees: Withholding, Estimated Taxes, and the December RMD Move

Most tax problems retirees run into aren't caused by exotic strategies — they're caused by withholding that quietly stopped matching reality. A pension started, a Social Security benefit began, an IRA distribution was larger than planned, and suddenly next April brings a bill plus an underpayment penalty. July, the halfway point of the tax year, is the natural moment to check — while there's still time to fix things cheaply.

Why do retirees get surprised by underpayment penalties?

When you were working, your employer's withholding usually tracked your income automatically. In retirement, income arrives from several places — Social Security, pensions, IRA withdrawals, interest, dividends, capital gains — and each has its own withholding rules, many defaulting to little or nothing. The IRS still expects tax to be paid as income is received, not just by April 15. Pay too little during the year and an underpayment penalty can apply even if you settle up in full at filing time, as explained in IRS Publication 505, Tax Withholding and Estimated Tax.

What are the safe harbor rules?

You generally avoid an underpayment penalty if, through withholding and timely estimated payments, you pay the smaller of 90% of this year's tax or 100% of last year's tax — which rises to 110% of last year's tax if your prior-year adjusted gross income exceeded $150,000 ($75,000 married filing separately), per Publication 505.

A mid-year checkup is simple in concept: estimate your 2026 income, project the tax, and compare it against what your withholding and estimated payments will actually total by December. If there's a gap, you have two main tools — and the next quarterly estimated payment deadline is September 15, 2026.

What is the December RMD withholding move?

Here is the technique many retirees don't know about. Estimated payments are credited when paid — a September payment doesn't cure a shortfall from March. But tax withheld from income is treated as if it were paid evenly throughout the year, regardless of when it was actually withheld, per IRS guidance on estimated tax and Publication 505.

That creates a clean fix for anyone taking a required minimum distribution — currently required beginning at age 73, with the annual deadline of December 31. If you discover in the fall that you're under-withheld for the whole year, you can ask your IRA custodian to withhold a large portion of a year-end distribution for taxes. Because withholding is deemed paid evenly across all four quarters, that single December withholding can retroactively cure underpayments from January onward — something no estimated payment can do.

A note worth highlighting: Whether this makes sense depends on the size of your RMD relative to the shortfall, your cash-flow needs, and your state tax picture. It is a useful repair tool — not a substitute for keeping withholding roughly right all year.

What else belongs in a mid-year checkup?

• New 2026 deductions may have changed your math. Recent law changes — including the $6,000 senior deduction and the expanded SALT cap — may lower your projected tax, meaning some retirees are now over-withheld.
• Planned one-time income. A large capital gain, home sale, or Roth conversion later this year raises the required payments; better to plan the withholding now than to discover the penalty later.
• Contribution room. If you or a spouse still have earned income, mid-year is a sensible time to check progress against the 2026 IRA and 401(k) contribution limits.

The bottom line

A one-hour mid-year review — project the year's income, check it against the safe harbor, and adjust withholding or the September 15 estimated payment — prevents the most common and most avoidable tax penalty in retirement. And if the year gets away from you, the December RMD withholding technique is a legitimate, IRS-recognized way to catch up. The right combination depends on your income sources, your age, and your state — a conversation worth having with your tax professional before the fall.

This article is general educational information, not tax or investment advice. The rules summarized here — safe harbor percentages, deadlines, and RMD requirements — are set by the IRS and depend on your specific income, filing status, and circumstances. Consult a qualified tax professional before acting.