The tax mechanics for someone working and collecting retirement income at the same time aren't actually complicated, everything, wages, Social Security (to the extent taxable), pension payments, and any retirement account withdrawals, gets added together on the same federal return and taxed at your marginal bracket for that combined total. The complexity is less about the tax calculation itself and more about the several separate rules that interact with it, the earnings test, the Social Security taxation formula, and MAGI-based thresholds elsewhere in the tax code.

The Social Security earnings test only applies if you're collecting benefits before your full retirement age. For 2026, if you're under full retirement age all year, $1 in benefits is withheld for every $2 you earn above $24,480. In the calendar year you reach full retirement age, the limit is more generous, $65,160, with only $1 withheld for every $3 earned above it, counting only earnings before the month you reach full retirement age. Once you're at full retirement age, this test disappears entirely, you can earn any amount of wages or self-employment income with zero reduction to your Social Security benefit.

The earnings test only counts wages and net self-employment earnings, it specifically does not count pension payments, annuity income, investment income, interest, or other retirement account withdrawals. A retiree drawing a large pension and taking IRA withdrawals while also working part-time only has the part-time wages counted against the earnings limit, not the pension or IRA income.

Money withheld under the earnings test isn't simply lost. Once you reach full retirement age, Social Security recalculates your benefit going forward to credit you for the months benefits were reduced or withheld, which raises your ongoing monthly benefit for the rest of your life. This is a common point of confusion, people often describe the earnings test as a penalty when it's more accurately a deferral with a later benefit increase built in.

The bigger, less visible effect of continuing to work is on modified adjusted gross income (MAGI), which drives several thresholds that have nothing directly to do with the earnings test. Additional wage income raises provisional income, which can push a larger share of Social Security into taxable territory. It can also push MAGI over Medicare IRMAA thresholds (raising Part B and Part D premiums two years later) or over the ACA premium tax credit's income limits if you're buying marketplace health insurance before Medicare eligibility.

For someone drawing RMDs while also working, there's no special coordination rule, the RMD is required regardless of employment status once you're past the applicable age, with one narrow exception: the 'still working' exception lets you delay RMDs from your current employer's 401(k) (not an IRA, and not a prior employer's plan) if you're still employed there past your RMD age and don't own more than 5% of the company. That exception is specific and easy to misapply to accounts it doesn't actually cover.

State tax on the combined income follows whatever rules apply where you live, layered on top of the federal picture rather than replacing it. A retiree in Arizona working part-time while collecting Social Security and taking RMDs pays no state tax on the Social Security, and a flat 2.5% on the wages and RMD income; the same household in California would owe nothing on Social Security but face California's graduated rates, up to 9.3% for a meaningful range of income, on the wages and RMD combined.

If you're collecting Social Security before full retirement age and considering part-time work or consulting income, run the earnings-test math before assuming the extra income is a straightforward win. It usually still is over your lifetime, once the later benefit recalculation is factored in, but the near-term reduction can be a real cash-flow surprise if you weren't expecting it.

If you're working and also taking RMDs or other retirement account withdrawals, model the combined effect on IRMAA and, if relevant, ACA subsidy thresholds before the income shows up on your return. The tax bracket effect of extra income is usually the smallest part of the total cost; the MAGI-driven Medicare and ACA effects are frequently larger and easier to miss.

• Assuming the Social Security earnings test is a straightforward penalty rather than a temporary reduction that gets credited back through a higher benefit later.
• Applying the earnings test to pension, annuity, or investment income, it only counts wages and net self-employment earnings.
• Not checking whether continued employment income pushes MAGI over an IRMAA or ACA subsidy threshold, separate from the ordinary income tax bracket effect.
• Misapplying the 'still working' RMD delay exception to an IRA or a former employer's plan, it only applies to your current employer's plan if you're still working there and don't own more than 5% of the company.