1099 Moonlighting Taxes for Physicians (2026): Self-Employment Tax, the Permanent QBI Deduction, Quarterly Payments, and the Solo 401(k) Play

Why 1099 income changes your tax picture

A meaningful and growing share of physician income now arrives on a 1099 instead of a W-2: moonlighting shifts during residency or fellowship, weekend or evening urgent care work for an attending who already has a full-time hospital job, locum tenens assignments between permanent positions, telemedicine panels, and expert-witness or medical-director work paid outside payroll. The moment income shows up on a 1099-NEC instead of a W-2, a different set of tax mechanics applies — self-employment tax, a possible qualified business income (QBI) deduction, a quarterly payment obligation, and access to a retirement plan reserved for the self-employed. None of it is intuitive if your only tax experience is a single hospital W-2, and getting it wrong is expensive.

The core tension for physicians is that the same 1099 mechanics behave very differently depending on how much you also earn as a W-2 employee. A moonlighting resident and an attending with a six-figure hospital salary can have the identical $20,000 of 1099 profit and end up with meaningfully different tax results — different self-employment tax, different QBI eligibility, different retirement-plan opportunity. That asymmetry, and how to plan around it using verified 2026 IRS and Social Security Administration (SSA) figures, is the throughline of this guide.

Self-employment tax: the 15.3% baseline

1099 income has no employer withholding Social Security or Medicare tax on your behalf, so the IRS collects both halves directly from you as self-employment (SE) tax. Per the IRS's Self-Employment Tax page, SE tax is 15.3% — 12.4% for Social Security and 2.9% for Medicare — applied to 92.35% of your net self-employment earnings, a standard adjustment made on Schedule SE. You can then deduct half of the SE tax you pay against your income tax, which softens the total bill somewhat.

For a physician with no other Social Security wages, the 12.4% portion applies only up to the annual Social Security wage base. Above that ceiling, only the 2.9% Medicare portion continues, uncapped. That baseline is identical for every self-employed taxpayer. What changes for most physicians is what happens once a W-2 salary is added to the picture.

The nuance that matters most: your W-2 salary counts first

This is the single most important mechanic in this article for anyone with a full-time hospital paycheck. Social Security tax — whether withheld from a W-2 or paid through SE tax — is capped in total across all of your earnings for the year, not per job. Your W-2 wages count against the annual wage base first, before any 1099 income is considered. Per the Social Security Administration's Contribution and Benefit Base page, that wage base is $184,500 for 2026 — up from $176,100 in 2025, announced October 24, 2025 — with a maximum Social Security contribution of $11,439 per side.

Practical effect: if your attending W-2 salary already meets or exceeds $184,500, your hospital has already covered your full share of the 12.4% Social Security tax for the year. Your moonlighting or locum 1099 income then owes no additional 12.4% Social Security portion at all — only the 2.9% Medicare portion of SE tax. You may also owe the Additional Medicare Tax of 0.9% once your combined wages and self-employment income exceed $200,000 (single) or $250,000 (married filing jointly), per the IRS's Additional Medicare Tax Q&A — thresholds that, unlike the wage base, are fixed by statute and not inflation-indexed.

A moonlighting resident or lower-earning locum physician sits in the opposite position: if combined W-2 wages and 1099 net earnings stay under $184,500, the full 12.4% Social Security portion applies to the 1099 income on top of the 2.9% Medicare portion — the complete 15.3% SE tax rate. Confirm the exact interaction on Schedule SE with a CPA rather than estimating it yourself, since it depends on your precise combined earnings for the year.

The QBI deduction is now permanent — but physicians are a special case

The Tax Cuts and Jobs Act created a 20% qualified business income (QBI) deduction under Section 199A for eligible owners of sole proprietorships, partnerships, and S corporations, originally scheduled to expire at the end of 2025. The One Big Beautiful Bill Act, signed July 4, 2025, made the 20% QBI deduction permanent instead of letting it lapse. See the IRS's qualified business income deduction page and Tax Foundation's coverage of the Section 199A changes for background on the legislation.

The catch for physicians specifically: medicine is classified as a "specified service trade or business" (SSTB) under Section 199A, alongside law, accounting, and consulting. SSTB income loses the QBI deduction above certain taxable income levels. For 2026, the phase-out zone begins at $201,750 of taxable income for single filers and heads of household, and $403,500 for married filing jointly, extending $75,000 and $150,000 above those thresholds, respectively, before the deduction reaches zero. The Act also added a minimum QBI deduction of $400 for any taxpayer with at least $1,000 of qualifying business income from an active trade or business, starting in 2026 and indexed for inflation after that.

The resident-vs-attending asymmetry

Put the mechanics together and a clean pattern emerges. A moonlighting resident or fellow, whose total taxable income is almost always well under $201,750 / $403,500, generally qualifies for the full 20% QBI deduction on 1099 moonlighting profit — a real, permanent benefit on top of everything else. A high-earning attending, by contrast, is often already above the top of the phase-out range before adding any 1099 income, which means their moonlighting or locum profit typically gets little or no QBI deduction, purely because medicine is an SSTB.

The same 1099 income, from the same kind of shift, can be fully QBI-eligible for a resident and essentially QBI-ineligible for an attending. It doesn't change whether the 1099 work is worth doing — it changes how much of the profit survives taxation, and it's worth modeling with a CPA before assuming a deduction that may not apply at your income level.

Quarterly estimated payments: due dates and the safe harbor

Because no one withholds tax from a 1099 payment, the IRS expects tax to be paid as you earn it, in quarterly installments, rather than in one lump sum at filing. Per the IRS's Estimated Taxes page, missing a due date can trigger an underpayment penalty even if you're due a refund overall when you file.

Due dates per the IRS Estimated Taxes page, current as of July 2026. Confirm current-year dates on IRS.gov before filing.

You can avoid the penalty by meeting a safe harbor: pay at least 100% of your prior year's total tax liability (110% if your prior-year adjusted gross income exceeded $150,000), or 90% of your current year's actual liability, whichever is smaller. Use Form 1040-ES to calculate the estimate.

A trick that works well for physicians who also have a W-2 job: increase your hospital withholding late in the year to cover the gap from moonlighting income. The IRS treats withholding as paid evenly throughout the year regardless of when it's actually withheld, unlike an estimated payment, which only counts from the date paid — so a fourth-quarter withholding increase can retroactively cover earlier quarters in a way a catch-up estimated payment cannot. Coordinate this with a CPA or your hospital's payroll office.

The solo 401(k) play: a second retirement plan funded by moonlighting income

1099 income unlocks a retirement plan most fully employed physicians never access: a solo 401(k), or one-participant 401(k), available to anyone with self-employment income and no non-spouse employees. Our solo 401(k) vs. SEP IRA comparison verified the 2026 figures directly against IRS Notice 2025-67; this section applies them to moonlighting income specifically.

The employee elective deferral limit for 2026 is $24,500 — a per-person limit across every 401(k) plan you participate in during the year, including your hospital's plan, not a separate $24,500 for each plan. If your hospital 401(k) already has your full deferral for the year, your solo 401(k) employee-deferral room is already used.

The employer side is where moonlighting income earns its own space. The solo 401(k)'s employer profit-sharing contribution — roughly 20% of net self-employment earnings — sits under the overall $72,000 Section 415(c) cap, and that cap applies separately to each unrelated employer's plan. Your hospital 401(k) and a solo 401(k) funded by your own 1099 business are unrelated plans. That means even an attending who has already maxed the $24,500 employee deferral at the hospital can still open a solo 401(k) for moonlighting income and fund the employer profit-sharing side — a separate pool of tax-deferred space, up to roughly 20% of net moonlighting earnings, subject to a $360,000 compensation cap. This is often the single highest-value move available to an attending moonlighting on the side.

Stacking the deductions and choosing an entity

By filing time, a physician with 1099 moonlighting income typically stacks several deductions: half of the SE tax paid, any solo 401(k) contribution, the QBI deduction if taxable income is under the SSTB threshold, and ordinary business expenses tied to the 1099 work — state licensure fees, DEA registration fees for that specific work, malpractice or tail coverage for the 1099 activity, continuing medical education, and equipment. Home-office and mileage deductions can apply, but only where the facts genuinely support them — a space used regularly and exclusively for the 1099 business, or documented business mileage. A separate bank account for 1099 income and expenses makes all of this far easier to substantiate. A 1099-NEC generally arrives from any payer who paid you $600 or more for the work — confirm the current-year reporting threshold, since these rules have been in flux. See our physician tax reduction strategies guide for a broader menu of levers beyond 1099 income specifically.

On entity choice: for most moonlighting, locum, and side-gig physicians, filing as a sole proprietor on Schedule C is the default, and it's usually correct — minimal paperwork, no separate return, no payroll. An S-corporation election can reduce SE tax by splitting income into salary and distribution, but the added payroll, reasonable-compensation rules, and a separate corporate return rarely pay for themselves until 1099 profit reaches a sustained, meaningfully high six-figure level — and an S-corp does nothing about the SSTB/QBI phase-out, since physician income is SSTB regardless of the entity wrapped around it.

Putting it together for your situation

The mechanics above compound differently depending on where you sit. A moonlighting resident with a modest stipend from extra shifts typically sees the full 15.3% SE tax, a full QBI deduction, and a real employee-deferral opportunity in a solo 401(k) — a combination that makes the marginal tax cost of extra shifts lower than most residents assume; it's also worth revisiting your student loan strategy alongside any new moonlighting income. An attending with a maxed-out hospital salary above the wage base sees a lighter SE tax bite but usually loses the QBI deduction entirely, and should lean on the solo 401(k) employer contribution and ordinary business expenses instead. A full-time locum physician without a W-2 job at all is closer to a small-business owner for tax purposes and should treat quarterly payments, the solo 401(k), and entity choice as core parts of running that business, not an afterthought.

None of this replaces running your actual numbers. Confirm your specific wage-base interaction, QBI eligibility, and safe-harbor requirement with a CPA who works with physicians, and loop in a fee-only fiduciary advisor for how to prioritize solo 401(k) contributions against other goals. The rules here are precise enough that a small factual difference — a few thousand dollars of W-2 salary, a different filing status — can change the right answer.

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