I Have a W-2 Job and a 1099 Locum Side Gig. What Do I Set Up?
The honest answer is less than the internet tells you: a separate bank account, a bookkeeping habit, a solo 401(k), and restraint about entities you do not need yet.
A guide by Taxstra Tax & Accounting · CPA-led tax strategy for business owners
Written by Bryan Martin, CPA, Managing Partner and Founder of Taxstra. Last updated August 18, 2026.
The short answer
For most W-2 physicians picking up 1099 shifts, the right setup is simple: operate as a sole proprietor (or a single-member LLC if you want the legal wrapper; it changes nothing on your federal return), run the income and expenses through a dedicated bank account onto Schedule C, deduct your CME, licenses, and malpractice against it, open a solo 401(k) for employer contributions on top of your maxed hospital plan, and cover the tax through withholding or quarterlies. Skip the S-corp until the side gig is big enough to pay for its own overhead.
Sole prop vs LLC: a legal question wearing a tax costume
Federal tax does not care which one you pick. A single-member LLC is a disregarded entity: same Schedule C, same self-employment tax, same deductions as a sole proprietor. What the LLC buys you is a contracting identity and a liability shield for business obligations, and you should understand its limits: malpractice liability follows the clinician personally, which is why your malpractice policy, not your entity, is the real protection.
Reasons to bother with the LLC anyway: some hospitals and agencies prefer contracting with an entity, some states make it cheap and easy, and it forces the separation of finances you should have regardless. Reasons to skip it: annual fees and franchise taxes in some states, and zero federal tax benefit. Either answer is defensible. What is not defensible is the version where the entity substitutes for bookkeeping.
Do not S-corp a side gig by default
The deduction shift nobody explains to W-2 physicians
As a pure W-2 employee, your CME trips, license renewals, and society dues are generally nondeductible; the deduction for unreimbursed employee expenses is gone. The moment you have a genuine 1099 practice, the professional costs that serve it become Schedule C deductions: CME relevant to the locum work, state licenses, DEA registration, malpractice premiums for the 1099 coverage, credentialing, a home office if it genuinely qualifies, and mileage under the rules covered in our mileage guide.
Two honesty rules keep this clean. Allocate shared costs: a license that serves both jobs is not 100% a side-gig expense just because that is convenient. And the business has to be real: a weekend of shifts per month with real income supports real deductions; a 1099 that exists mainly to absorb your conference habit does not.
The solo 401(k): where the side gig earns its keep
Here is the piece worth the paperwork. Your employee deferral limit ($24,500 in 2026) is one bucket shared across every plan you participate in, so a maxed hospital 401(k) uses it up. But the employer contribution limit applies separately to unrelated employers, and your solo practice is an unrelated employer. It can contribute roughly 20% of your net self-employment earnings to your own solo 401(k), on top of everything happening at the hospital.
Hospitalist, $310K W-2 plus $60K of weekend locum shifts
- Hospital 401(k): employee deferral maxed
- $24,500
- Hospital match
- whatever the plan gives
- Locum net profit after expenses
- $54,000
- Solo 401(k) employer contribution (~20% of net SE earnings after the SE-tax adjustment)
- roughly $10,000
- Federal tax saved at a 35% marginal rate
- roughly $3,500 this year, tax-deferred growth after that
The side gig did not just add income; it opened retirement space a W-2 alone cannot reach. Numbers are rounded and illustrative; the exact employer contribution comes off your Schedule C math.
One more setup item people forget: taxes on the side income itself, which you can handle with quarterly estimates or by raising your W-2 withholding. The mechanics, including the multi-state wrinkle when your shifts cross a border, are in How Do Locums Pay Quarterly Taxes in 4+ States? and Which State Do I Pay?
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Frequently Asked Questions
Do I need an LLC for a 1099 locum side gig?
Not for tax reasons. A single-member LLC is disregarded for federal tax: you file the same Schedule C either way. The LLC is a legal liability and contracting decision, and for a clinician the malpractice exposure runs to you personally regardless of entity. Plenty of side-gig locums operate as sole proprietors with good malpractice coverage and clean books.
Should I elect S-corp status for my locum side income?
Usually not at side-gig volume. S-corp savings come from splitting profit between a reasonable salary and distributions, and on a modest side income the required salary eats most of the profit while payroll, filing, and admin costs eat the rest. The election starts earning its keep when net locum profit is sustained and well into six figures, and it interacts with your W-2 Social Security wages, so run the math before filing Form 2553.
Can I deduct CME, licenses, and DEA fees against my 1099 income?
Yes, if they are ordinary and necessary for the 1099 work: CME, state licenses, DEA registration, malpractice premiums, credentialing fees, professional society dues, and supplies all belong on Schedule C. As a W-2 employee you generally cannot deduct unreimbursed job expenses under current law, which is exactly why routing professional costs through the side business, where legitimate, matters.
Can I have a solo 401(k) if I already max my hospital 401(k)?
Yes, and it is the single best tax feature of a locum side gig. Your employee deferral limit ($24,500 for 2026) is shared across all plans, so if the hospital plan takes it, your solo 401(k) deferral space is used up. But employer profit-sharing contributions, roughly 20% of net self-employment earnings, have their own separate limit at an unrelated employer. Side income can fund meaningful additional pre-tax savings.
How do I pay taxes on side-gig locum income during the year?
Two options: make quarterly estimated payments on the 1099 profit, or raise the withholding at your W-2 job to cover it. Withholding is treated as paid evenly through the year, which makes it the simplest safe-harbor tool for a W-2 physician adding a side gig mid-year.
Do I need an EIN for the side gig?
You need one for a solo 401(k) and for any entity or payroll, and even a plain sole proprietor should get one anyway: it takes minutes online, it goes on the W-9s that agencies and facilities demand, and it keeps your Social Security number out of a dozen vendor systems. There is no downside, and the identity-hygiene upside alone justifies it in week one.
Related Locum Tenens Tax Questions
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This page is educational, not individualized tax advice. Locum tenens tax outcomes depend on your contracts, your states, and your numbers. Savings vary by client and results are not typical of every situation. Consult a qualified tax professional before acting on anything here.