Six Tax Mistakes 1099 Physicians Make

Remaining a Sole Proprietor Past the S-Corp Threshold

Physicians earning $150,000 or more in net 1099 income who remain sole proprietors pay self-employment tax on 100% of their income. An S-Corporation structure splits income into salary and distributions. Only the salary portion incurs payroll taxes. This difference generates annual savings of $12,000 to $22,000 for most physicians.

The administrative costs of S-Corporation operation include payroll processing, a separate business tax return, and increased bookkeeping complexity. These costs total approximately $3,000 to $5,000 annually. The breakeven threshold occurs at approximately $130,000 in net income. Above this level, tax savings exceed administrative costs.

Common reasons for delayed S-Corporation formation include perceived complexity of the process, uncertainty about income stability, and incorrect guidance from CPAs who recommend waiting until income reaches higher thresholds. The formation process takes two to four weeks and can be completed mid-year with prorated benefits for the remainder of the tax year.

Setting S-Corporation Salary Incorrectly

The IRS requires S-Corporation owners to pay themselves reasonable compensation for services performed. Salary set too low triggers audit risk and potential reclassification of distributions as wages. Salary set too high generates unnecessary payroll taxes and reduces the Qualified Business Income deduction base.

Most generalist CPAs apply arbitrary percentages such as 40% or 50% without specialty-specific justification. The IRS reviews S-Corporation salary levels using industry compensation data. For physicians, this means MGMA (Medical Group Management Association) benchmarks organized by specialty, region, and years of experience.

Crossing the QBI Threshold and Losing the Deduction

The Qualified Business Income deduction phases out beginning at $403,500 in taxable income for married filers in 2026. The phase-out range extends to $553,500, at which point physicians classified as Specified Service Trade or Businesses lose the deduction entirely.

Taxable income is calculated after all above-the-line deductions. This includes Solo 401(k) contributions, self-employed health insurance premiums, the self-employment tax deduction, and either the standard deduction or itemized deductions. A physician earning $500,000 in gross 1099 income can remain below the $403,500 threshold if deductions total $96,500 or more.

Most CPAs calculate QBI eligibility once per year during tax preparation. This creates a timing problem. By April, the tax year has closed and no adjustments are possible. A physician who discovers in April that their taxable income was $410,000 has already lost a portion of the deduction. A $10,000 Solo 401(k) contribution made before December 31st would have preserved it.

Inadequate Business Expense Tracking

Locum tenens and independent contractor physicians incur substantial deductible business expenses. These include mileage to assignment locations, CME courses, multi-state medical licensing fees, DEA registrations, malpractice tail coverage, professional memberships, medical subscriptions, equipment purchases, and home office expenses for administrative work.

Without systematic tracking, physicians typically fail to document 30% to 50% of legitimate business expenses. At a 37% marginal federal tax rate plus state taxes, $35,000 in missed deductions costs approximately $14,000 in unnecessary tax payments.

The IRS requires contemporaneous records for certain deductions. Mileage logs must be maintained during the year, not reconstructed at tax time. Receipts for expenses over $75 must be retained. Home office deductions require documentation of exclusive business use for a dedicated space.

Underpaying or Missing Estimated Tax Deadlines

The IRS requires quarterly estimated tax payments for taxpayers without sufficient withholding. Penalties apply when payments fall short of 90% of current year tax or 110% of prior year tax (for high earners). The penalty rate approximates 7% annually, calculated from each quarterly deadline.

Variable 1099 income creates estimation challenges. A physician earning $220,000 one year and $310,000 the next who bases quarterly payments on prior year amounts will underpay by $26,000. The resulting penalties and interest total approximately $1,800 to $2,200.

The quarterly deadlines are not evenly spaced: April 15, June 15, September 15, and January 15 of the following year. Missing a deadline by one day triggers penalties calculated from the due date. Late payment on one quarter while meeting requirements on others still generates partial-year penalties.

Selecting SEP IRA Over Solo 401(k)

SEP IRAs and Solo 401(k) plans both allow maximum contributions of approximately $69,000 for 2026. The critical difference lies in contribution mechanics and Roth conversion opportunities. SEP IRAs accept only employer contributions calculated as a percentage of compensation. Solo 401(k) plans accept both employee deferrals and employer contributions, and with proper plan documentation, allow after-tax contributions that can be immediately converted to Roth.

This Mega Backdoor Roth strategy permits high-earning physicians to shelter an additional $50,000 to $100,000 annually beyond standard contribution limits. The after-tax contributions convert to Roth with minimal tax impact if done immediately, then grow tax-free indefinitely.

Not all Solo 401(k) providers offer the plan provisions required for Mega Backdoor Roth contributions. The plan document must explicitly allow after-tax employee contributions and either in-service distributions or in-plan Roth conversions. Providers such as Fidelity, Schwab, and specialized Solo 401(k) administrators offer these features, but they must be specifically requested during plan setup.