Most physicians who transition to locum tenens focus on the upside: higher hourly rates, schedule control, and the freedom to practice across different environments. What catches many off guard is the tax structure that comes with 1099 status — and how dramatically it differs from being a W-2 employee.
As an independent contractor, you're responsible for both the employer and employee portions of Social Security and Medicare taxes, you won't have automatic withholding, and you'll face a quarterly estimated payment schedule that punishes the unprepared. But the same independent contractor status that creates those obligations also opens access to a deduction toolkit that W-2 physicians simply don't have.
Understanding this toolkit is not optional. At typical locum physician income levels — often $250,000 to $500,000 or more annually — the difference between an optimized and unoptimized tax posture can be $40,000 to $100,000 per year. That's not a rounding error. It's a retirement account, a second home, or several years of financial runway.
This guide covers the strategies that actually move the needle.
The 1099 Tax Baseline: What You're Actually Paying
Before optimizing, you need to understand what you're paying as a baseline.
As a sole proprietor receiving 1099 income, your effective tax burden comes from three sources:
Self-employment tax. The self-employment tax rate is 15.3% on the first $168,600 of net self-employment income (2024 threshold) and 2.9% above that figure. This covers both the employer and employee shares of Social Security and Medicare — a 7.65% overhead that your permanently employed peers never see on their pay stubs because their employer absorbs half.
Federal income tax. Net self-employment income is subject to ordinary federal income tax rates, which reach 37% for income above $609,350 (single) or $731,200 (married filing jointly) in 2024.
State income tax. Varies by state and adds complexity for locum physicians working across multiple states (more on this below).
At $300,000 net self-employment income, a physician with no optimization strategy might face an effective rate approaching 45–50% all-in when federal income tax, self-employment tax, and state taxes are combined. That figure is the starting point — not the floor.
S-Corporation Election: The Single Largest Lever
For most locum physicians earning above approximately $80,000 in net self-employment income annually, forming an S-corporation (or electing S-corp tax treatment for an LLC) is the highest-impact structural decision available.
Here's why: S-corp owners pay self-employment taxes only on the "reasonable compensation" salary they pay themselves — not on all business profits. Distributions above that salary pass through as ordinary income without triggering self-employment tax.
Simplified example:
- $300,000 net income, sole proprietor: self-employment tax applies to approximately $300,000 → ~$22,000 in SE tax on first $168,600 + 2.9% above
- $300,000 net income, S-corp with $120,000 salary: SE tax applies only to $120,000 salary → roughly $17,000 in SE tax
- Savings: ~$5,000–$10,000 depending on income level
The savings scale significantly with income. A physician earning $500,000 annually might save $15,000–$25,000 per year in self-employment taxes through S-corp structuring.
What "reasonable compensation" means in practice. The IRS requires that S-corp owners who perform services for the corporation pay themselves a reasonable salary — roughly what the business would pay an unrelated employee to perform the same work. For physicians, "reasonable" compensation is well-documented and defensible. Setting your salary too low is an audit risk; setting it appropriately and taking the remainder as distributions is sound tax planning.
Costs to consider. S-corp election adds administrative overhead: payroll processing, quarterly payroll tax filings, and typically a more complex annual return. Most physicians working with a CPA experienced in physician finances can expect to spend $2,000–$5,000 annually in additional accounting costs — easily offset by the tax savings.
If you're reviewing your income potential before making this decision, the physician pay guide breaks down typical earnings by specialty and geography so you can model your numbers accurately.
Retirement Accounts: Sheltering Six Figures from Taxation
The retirement account options available to self-employed physicians are substantially more powerful than anything available to W-2 employees.
Solo 401(k). For physicians working through a single-member entity with no full-time employees, the solo 401(k) is often the optimal vehicle. In 2024, contributions can reach $69,000 ($76,500 if you're 50 or older):
- Employee elective deferral: up to $23,000 ($30,500 if 50+)
- Employer profit-sharing contribution: up to 25% of W-2 compensation (for S-corp owners) or 20% of net self-employment income (for sole proprietors)
SEP-IRA. Simpler to administer than a solo 401(k) and available until the tax-filing deadline (including extensions). Contribution limit is 25% of W-2 compensation or 20% of net self-employment income, up to $69,000 in 2024. No catch-up contributions available. Useful for physicians who want minimal administration, but it leaves money on the table compared to the solo 401(k) for those who can contribute the full employee deferral.
Defined benefit plan. For high-earning physicians over 45 who want to shelter more income than the solo 401(k) allows, defined benefit plans can permit contributions exceeding $200,000 annually. These plans require actuarial calculations and ongoing administration, but the tax shelter they create can be enormous in the final decade before retirement.
The compounding effect. At $300,000 annual income with a solo 401(k) maxed at $69,000, you're sheltering roughly 23% of gross income from current taxation. At a 35% marginal federal rate, that's approximately $24,000 in deferred federal taxes per year — money that compounds inside the account tax-deferred until withdrawal.
Business Deductions: The Locum Physician's Advantage
Independent contractor status opens the door to deductions that W-2 physicians cannot access. The most valuable categories:
Travel and Transportation
Locum physicians traveling away from their tax home for work can deduct reasonable travel expenses — airfare, ground transportation, lodging, and 50% of meal costs incurred while traveling. When an assignment takes you more than 50 miles from your tax home, these expenses are deductible as business expenses on Schedule C or your entity return.
Tax home matters. Your "tax home" is generally your principal place of business, not your personal residence. For locum physicians who work in multiple locations without a fixed primary practice location, establishing and documenting a tax home requires deliberate planning. This is one of the areas where physician-specific tax expertise is most valuable — mistakes here trigger audits and disallowances.
Per diem rates. The IRS publishes per diem rates for lodging and meals by location. Using the standard per diem (rather than tracking actual receipts) simplifies documentation considerably while still providing a substantial deduction.
Home Office
If you use a dedicated portion of your home exclusively and regularly for business — managing contracts, billing, continuing education, licensing paperwork — the home office deduction applies. The simplified method ($5/square foot, up to 300 square feet) provides a clean deduction without complex calculations. The regular method (actual expenses proportionate to office square footage) is larger but requires more documentation.
Professional Expenses
All costs directly related to maintaining your ability to practice are deductible:
- Medical licensure fees (including multi-state licenses)
- DEA registration and renewals
- Board certification and maintenance of certification fees
- CME courses, medical conferences, and related travel
- Professional liability (malpractice) insurance premiums
- Medical association dues and subscriptions
- Medical equipment and technology used in practice
Health Insurance Premiums
Self-employed physicians can deduct 100% of health insurance premiums for themselves, their spouse, and dependents as an above-the-line deduction (reducing adjusted gross income before itemizing). This applies to medical, dental, and long-term care insurance. The deduction cannot exceed the net profit of the business, and it's not available in years when you're eligible for coverage through a spouse's employer.
Continuing Education and Professional Development
Every CME course, conference registration, journal subscription, and textbook purchased to maintain or improve skills required in your current practice is deductible. For physicians with active practices, this category routinely totals $5,000–$15,000 annually.
The QBI Deduction: An Overlooked 20% Pass-Through Benefit
The Section 199A qualified business income (QBI) deduction allows eligible pass-through business owners to deduct up to 20% of qualified business income. For physicians — a "specified service trade or business" (SSTB) — the deduction phases out completely once taxable income exceeds $383,900 (married filing jointly, 2024).
This means high-earning locum physicians will often phase out of the QBI deduction entirely. But physicians near the threshold — particularly those with significant retirement contributions reducing taxable income — can preserve a meaningful portion of the deduction. The interaction between retirement contributions and QBI deduction eligibility is a real optimization lever worth running through your CPA.
Multi-State Taxation: The Locum-Specific Complication
A locum physician working in three states during the year owes state income tax in each state for income earned there (in states that have an income tax). This creates both a compliance burden and, potentially, a planning opportunity.
Key rules to understand:
- You generally owe state income tax where the services were performed, not where you live
- Your home state may credit taxes paid to other states, preventing true double taxation — but only up to the amount it would have charged on the same income
- Some states are more aggressive in asserting nexus for short-term workers; others have safe harbors for workers present for fewer than a certain number of days
For physicians targeting high-volume locum work across multiple states, working with a tax professional who understands the allocation rules matters more than almost any other variable. The penalty exposure from incorrect multi-state filings is significant, and the optimization opportunities (e.g., structuring work to maximize time in lower-tax states) are real but require careful documentation.
Quarterly Estimated Taxes: Avoiding the Underpayment Penalty
Unlike W-2 employees, independent contractors don't have taxes withheld from each paycheck. Instead, you're required to make quarterly estimated tax payments. Missing these or significantly underpaying triggers penalties from both the IRS and most states.
The safe harbor approach. The IRS won't assess underpayment penalties if you pay either 100% of the prior year's tax liability (or 110% if your prior year AGI exceeded $150,000) or 90% of the current year's liability. Most physicians find the prior-year safe harbor easier to calculate and use as a baseline.
Payment schedule. Estimated payments are due April 15, June 15, September 15, and January 15 of the following year for income earned in the preceding quarter. The IRS Form 1040-ES and state equivalent forms handle the mechanics.
Cash flow implication. This payment cadence requires maintaining a tax reserve throughout the year. A common approach: deposit 35–40% of each gross payment received into a dedicated tax savings account and make quarterly draws from that account for estimated payments.
Structuring Your Practice: Practical Checklist
For a physician moving into or optimizing a locum practice from a tax standpoint:
- Determine whether to operate as sole proprietor or S-corp based on annual income — consult a CPA with physician clients before deciding
- Open a business checking account and keep business and personal finances strictly separated
- Establish a retirement account (solo 401(k) preferred for most; SEP-IRA if simplicity is the priority) and fund it aggressively
- Set up quarterly estimated tax payments before the first payment deadline — not after a year of missed payments
- Begin tracking all deductible expenses from the first day of independent contractor work — receipts, mileage logs, and documentation are far easier to maintain in real time than reconstruct later
- Engage a CPA with physician-specific experience before or in the first year of locum work — not a general practice CPA who hasn't dealt with multi-state returns, medical licensure, and per diem rules
- Review the QBI deduction eligibility annually as income changes — it's highly income-sensitive and easy to lose track of amid other planning
What This Looks Like in Practice
A physician earning $350,000 in gross 1099 locum income, working through an S-corp, might structure their tax position as follows:
- Reasonable salary: $130,000 → SE tax on $130,000 (vs. $350,000 without S-corp)
- Solo 401(k): $69,000 contribution (employee deferral + profit sharing)
- Health insurance deduction: $18,000
- Travel and lodging (documented): $22,000
- Professional expenses and CME: $8,000
- Home office: $3,000
Taxable income after deductions: approximately $230,000 (vs. $350,000 without planning)
Federal income tax savings: $40,000–$50,000 annually
SE tax savings vs. unstructured sole prop: $12,000–$18,000 annually
None of these are aggressive positions. They're the standard toolkit for a self-employed physician who has implemented basic best practices — and they're available to any locum physician willing to set up the right structure and maintain adequate documentation.
The Foundation
Tax optimization for locum physicians isn't exotic. It's a defined set of structures and deductions applied consistently with good documentation. The physicians who pay the most aren't doing so because the options don't exist — they're paying the most because they haven't yet engaged with a CPA who understands the full toolkit available to them.
If you're still evaluating whether locum tenens income justifies this kind of structural attention, the locum tenens 101 guide covers the full landscape of what independent contractor practice involves — the logistics, the opportunities, and the tradeoffs — alongside the financial upside that makes the planning worthwhile.
The floor for what's possible is whatever you pay without planning. Everything above that is a choice.