The first paycheck after the jump is a rite of passage. You finish residency in June, start the attending job in July, and the first real deposit lands — noticeably smaller than the offer letter divided by pay periods. The instinct is that payroll made a mistake. Payroll did not make a mistake; payroll made an assumption. Federal withholding treats every paycheck as if it were one of an identical series stretching across the whole year, and in the year you change income mid-stream, that assumption is wrong in a predictable direction. This article shows the exact mechanics, works the resident-to-attending numbers, explains why bonuses fail in the opposite direction, and walks through the three W-4 levers that put you back in control.
Payroll assumes every paycheck is forever
The federal withholding computation your employer runs is the percentage method in IRS Publication 15-T (2026), and its logic is annualization. For each paycheck, the payroll system multiplies your wages for the period by the number of pay periods in the year to get an annualized wage figure, looks that figure up in the annual percentage-method tables — which mirror the real tax brackets — computes a tentative full-year tax, and divides the result back by the number of pay periods. That quotient is the withholding on your check.
Read that again with a July raise in mind. The system does not know your income history and does not care. Each paycheck is withheld as if you earned at that rate for all twelve months, so the year you jump from resident to attending pay, every attending check is withheld as if the attending salary were your full-year income — which it is not. Your actual year is a blend: six months at the old rate, six at the new. The withholding tables have no blended row.
The same machinery explains the pleasant surprise in the opposite direction that many interns notice: a half-year of resident salary starting in July is withheld as if the resident salary ran all year, which slightly over-withholds too, but the dollars are small. At attending pay, the dollars are not small. The first-attending-paycheck module walks the whole first stub line by line; here we isolate the federal income tax line.
The year of the jump, you are over-withheld — by about $5,300 in this example
Work it precisely with 2026 numbers.
Example calculation
Assumptions, stated explicitly: single filer; monthly payroll; resident salary of $70,000 through June 30; attending salary of $320,000 from July 1; W-4 with Step 1 only (no Step 2 checkbox, no dependents, no extra withholding); standard deduction of $16,100 (Rev. Proc. 2025-32); 2026 single brackets; federal income tax only — FICA and state tax excluded; simplified by applying the annual tables directly, so treat results as close approximations of Publication 15-T worksheet output.
Resident months, January–June: Annualized wages: $5,833.33 × 12 = $70,000 Tax on $70,000 − $16,100 = $53,900 taxable: $6,570 Withheld per month: $6,570 ÷ 12 = $547.50 — six months: $3,285
Attending months, July–December: Annualized wages: $26,666.67 × 12 = $320,000 Tax on $320,000 − $16,100 = $303,900 taxable: $75,134 Withheld per month: $75,134 ÷ 12 = $6,261 — six months: $37,567
Total withheld for the year: $3,285 + $37,567 = $40,852
Actual 2026 income: $35,000 (resident half) + $160,000 (attending half) = $195,000 Actual tax on $195,000 − $16,100 = $178,900 taxable: $35,534
Over-withholding: $40,852 − $35,534 = $5,318
Two things about that $5,318. First, it is a refund, not a loss — you get it back the following spring, having lent it to the Treasury at zero percent for up to a year. Second, the direction is reliable: in the year of an upward mid-year jump, annualized withholding on the new checks prices the whole year at the new rate while your true year blends the two, so the pure salary effect over-withholds. The July attending check is withheld at an effective rate built for a $320,000 year — 24, 32, and 35 percent bracket layers — while your actual $195,000 year tops out in the 24 percent bracket (2026 single brackets: 32 percent begins at $201,775 of taxable income, 35 percent at $256,225, per Rev. Proc. 2025-32).
The 2026 single rate schedule, for orientation:
| Rate | Taxable income (single) |
|---|---|
| 10% | $0 – $12,400 |
| 12% | $12,400 – $50,400 |
| 22% | $50,400 – $105,700 |
| 24% | $105,700 – $201,775 |
| 32% | $201,775 – $256,225 |
| 35% | $256,225 – $640,600 |
| 37% | over $640,600 |
Key insight
The over-withholding is a one-year phenomenon. In your first full calendar year at attending pay, the annualization assumption becomes true — every check really is one of twelve at the attending rate — and the withholding lands close to actual, provided your W-4 matches your household. The jump year is the anomaly, and it self-corrects at filing.
Bonuses fail in the opposite direction: 22 percent withheld, 32-plus owed
Supplemental wages — signing bonuses, relocation payments, quality incentives, reconciliations — usually bypass the annualization machinery entirely. Publication 15 (2026) lets employers withhold on supplemental wages at a flat 22 percent when paid separately from regular wages, with a mandatory 37 percent rate only on supplemental wages beyond $1,000,000 in a year — a line most physicians never approach.
For an attending, 22 percent is too low. A $40,000 signing bonus paid to a physician whose is 35 percent generates $8,800 of withholding against roughly $14,000 of actual tax — a $5,200 hole. So the jump year often nets two opposing errors: salary checks over-withhold, bonus checks under-withhold, and the April outcome depends on which effect is larger. The mechanics, including the aggregate-method alternative some payroll systems use, are covered in the supplemental wages article; and if the bonus pushes your Medicare wages past $200,000, the surtax article explains the extra 0.9 percent line that switches on.
Important
The most common genuinely bad outcome in the jump year belongs to two-earner couples. If both spouses file W-4s as married without checking the Step 2 box, each payroll system assumes it is withholding against the full married standard deduction and bracket widths — both cannot be right, and the couple under-withholds at exactly the income level where brackets steepen. A raise is the natural moment to fix Step 2 on both W-4s, not just the one at the new job.
The W-4 has no allowances anymore — it has three levers
If your mental model of the W-4 is claiming zero or one allowance, that form was retired. The redesigned W-4, in use since 2020 and current in its 2026 revision (irs.gov), asks for dollar-level facts instead, in five steps (Publication 505):
- Step 1 — filing status. This selects the standard deduction and bracket table payroll uses. Nothing else on the form matters as much per keystroke.
- Step 2 — multiple jobs or a working spouse. The checkbox splits the brackets in half so two payroll systems stop double-counting one standard deduction. Accuracy here fixes the two-earner failure above.
- Step 3 — dependents and credits, entered as annual dollar amounts that reduce withholding.
- Step 4 — the precision tools: 4(a) adds other income (, interest) into the withholding base, 4(b) adds deductions beyond the standard, and 4(c) adds a flat extra dollar amount per paycheck.
- Step 5 — signature.
Step 4(c) is the instrument that solves almost every physician withholding problem, because it is denominated in dollars per check rather than in assumptions. Know your projected shortfall — from a bonus, from moonlighting, from the 0.9 percent surtax — divide by remaining pay periods, and enter the result. Publication 15-T applies 4(c) after the annualization math, untouched by the tables.
Rather than reverse-engineering the worksheets by hand, run the IRS Tax Withholding Estimator (irs.gov) once mid-year: it takes year-to-date withholding from your stubs, projects the rest of the year at your actual mix of incomes — exactly what the paycheck-level tables cannot do — and outputs the W-4 entries. Fifteen minutes in July beats any amount of April arithmetic. For what each stub line should look like once your W-4 is right, see the paycheck-decoded module, and for the full projection workflow, the withholding guide.
Publication 505 lists the moments that should trigger a fresh W-4: marriage or divorce, a new job or a spouse starting one, a raise of more than $10,000 in regular wages, buying a home, and the arrival of nonwage income such as moonlighting. The resident-to-attending transition hits several of those at once.
Safe harbors mean you do not need to be perfect
The reason to fix withholding is cash-flow control, not penalty avoidance — because the underpayment penalty rules in section 6654 are forgiving, and never more so than in the jump year. You owe no underpayment penalty if any of these holds (Publication 505; IRS Topic 306):
- You owe less than $1,000 after subtracting withholding and refundable credits.
- Your withholding and timely estimates reach 90 percent of the current year's tax.
- They reach 100 percent of the prior year's tax — 110 percent if your prior-year AGI exceeded $150,000 ($75,000 married filing separately).
Look at lever three in the transition year. Your prior year was a resident year: total tax on roughly $70,000 might be $6,600. If your attending-year withholding merely matches 100 percent of that small number — which it will, many times over, by February — you cannot owe an underpayment penalty, no matter how large the April balance turns out to be. In the year you jump from resident to attending pay, the prior-year safe harbor is almost impossible to miss, so the worst realistic outcome of imperfect withholding is a bill, never a penalty. The 110 percent tier only becomes your number in later years, once a prior attending year (AGI above $150,000) is the baseline.
Quick takeaway
In the jump year: expect salary checks to over-withhold, expect bonuses at 22 percent to under-withhold, check the prior-year safe harbor so penalties stop worrying you, and run the Estimator once after your first attending stub to set Step 4(c). That is the entire protocol.
Common questions
My first attending paycheck withheld far more than one-twelfth of what an online calculator says I owe this year. Is payroll wrong?
No. Payroll annualizes each check in isolation, so your attending checks are withheld as if the attending salary ran all twelve months. Your actual year blends resident and attending pay, so the year-of-jump withholding overshoots and comes back as a refund. Starting with your first full calendar year, the assumption matches reality and the overshoot disappears.
Should I file a new W-4 the day I start the attending job?
Yes, if only to set Step 1 correctly and deal with Step 2 when you are married to another earner. Then refine once: after one or two attending stubs, run the IRS Tax Withholding Estimator with year-to-date numbers and enter its Step 4 outputs. Doing it in that order means the fine-tuning reflects real, not projected, withholding.
My signing bonus was withheld at 22 percent. Do I need to send the IRS the difference now?
Not necessarily. Test the safe harbors first: if your withholding this year will reach 100 percent of last year's total tax (a resident-year number), you face no penalty, and the shortfall is simply due in April. If you would rather not owe it then, divide the expected gap by remaining pay periods and put it on Step 4(c).
Does any of this change my state withholding?
State systems are separate and vary — many run their own annualization, some use flat supplemental rates, and a mid-year move between states adds part-year residency on top. The federal logic here does not transfer automatically; check your new state's withholding form in the same sitting.
What to do next
- Read the federal withholding line on your first post-raise stub and multiply by pay periods per year — that reveals the full-year income payroll is assuming, and the mismatch stops being mysterious.
- Confirm last year's total tax from your prior return (Form 1040, line 22) and note 100 percent of it as your penalty-proof floor for this year.
- File a W-4 at the new pay level: Step 1 filing status, and Step 2 checked on both spouses' forms if you are a two-earner household.
- After two attending stubs, run the IRS Tax Withholding Estimator with year-to-date figures and enter its recommended Step 3 and Step 4 amounts.
- When a bonus is scheduled, compute (marginal rate − 22 percent) × bonus, and either park that amount for April or spread it across Step 4(c).
- Recheck once each January — the first full attending year resets the math, and the 110 percent safe harbor becomes your number once prior-year AGI exceeds $150,000.
A raise changes your tax life less than the first distorted paycheck suggests; the machinery is annualization, and one afternoon with the Estimator brings withholding back into line — with or without any platform on top. This is education, not individualized financial advice.