Every July, in some workroom, a well-meaning senior says it: "Careful — the attending raise can push you into the next bracket, and you might take home less." It sounds prudent. It is also mathematically impossible.
Federal brackets are marginal: each rate applies only to the dollars inside its band. Crossing into a higher bracket re-taxes nothing behind you — the higher rate touches only the dollars above the line. What you actually pay is your effective rate: total tax divided by total income, blended across every band you passed through on the way up. A single attending earning $300,000 sits in the 35% bracket, but after the standard deduction the blended federal bill runs closer to a quarter of income. No raise, at any size, can shrink your take-home pay through brackets alone. Cliffs live in benefits and loan formulas, never in the brackets themselves.
Which makes your transition year the most interesting tax year you'll ever have. Finish training June 30, start attending pay in July, and the calendar year splits: half a resident salary plus half an attending salary. Your total taxable income lands a bracket or two below where you'll sit every year after: a one-time discount on every dollar you can shift into it. This is the year Roth contributions and conversions cost the least (the sequel to Issue No. 1's Roth Window), the year the "later" moves are cheapest. From January on, the discount is gone.
Two surprises wait in the paychecks themselves. Withholding tables annualize: your new employer withholds as if you had earned attending pay since January, so many first-year attendings quietly lend the IRS four or five figures, interest-free, until refund season. Moonlighting runs the opposite direction — 1099 income arrives with nothing withheld at all, and once your paycheck withholding stops covering last year's tax bill, the IRS expects quarterly estimated payments, not an April surprise. And if training and the new job sit in different states, you'll usually owe two part-year returns, each taxing only what you earned within its borders.
One fall evening with a paycheck stub and last year's return covers all of it: check the W-4, set aside a slice of any 1099 income, and decide what belongs in Roth while the blended rate lasts. Per hour, that evening pays better than the shift that funded it.