Moonlighting and Taxes - What Residents Get Wrong

Moonlighting can meaningfully boost your resident income. But the tax implications catch most residents off guard. Here is what you need to know before your first shift.

Moonlighting Income Is Self-Employment Income

When you moonlight as a resident - whether through your own program is approved opportunities or at an outside facility - you are typically paid as an independent contractor, not as an employee. That distinction has significant tax consequences that most residents do not anticipate until they owe a larger-than-expected tax bill.

As a W-2 employee at your residency program, your employer withholds federal and state income taxes and pays half of your FICA taxes - 7.65 percent of wages covering Social Security and Medicare. As an independent contractor, no taxes are withheld from your moonlighting checks, and you are responsible for both the employee and employer sides of FICA - a combined 15.3 percent on net self-employment income, in addition to federal and state income taxes. On a $30,000 moonlighting year, that self-employment tax alone is over $4,500 before income taxes are applied.

Estimated Taxes - What They Are and When to Pay Them

Because nothing is withheld from independent contractor income, the IRS expects you to pay taxes on that income quarterly rather than waiting until April. These are called estimated tax payments. The due dates for each tax year are typically mid-April, mid-June, mid-September, and mid-January of the following year.

If you underpay estimated taxes significantly during the year, you may owe a penalty in addition to the tax itself when you file. A simple way to avoid this is to set aside 30 to 35 percent of every moonlighting check in a separate savings account earmarked for taxes. When quarterly estimated payments are due, pay from that account. Whatever is left after you file your return is yours to keep. This approach prevents you from spending money that is not really yours and eliminates the April surprise.

Use IRS Form 1040-ES to calculate and submit quarterly estimated payments. Many residents find it easier to work with a CPA during their first moonlighting year to get the quarterly payments right and understand what deductions are available to offset self-employment income.

Deductions Available on Moonlighting Income

Self-employment income comes with deductions that W-2 income does not. The most significant is the self-employed health insurance deduction if you pay your own premiums. You can also deduct business expenses directly related to your moonlighting work: malpractice insurance premiums not covered by your program, licensing fees for states where you moonlight, continuing medical education costs, and professional dues.

More importantly, self-employment income opens the door to retirement contributions beyond what your residency program offers. You can contribute to a SEP-IRA based on your net moonlighting income - up to 25 percent of net self-employment earnings, with a 2025 maximum of $70,000. Even a modest SEP-IRA contribution reduces your taxable self-employment income dollar-for-dollar and starts building pre-tax retirement savings at a time when your overall tax rate is still relatively low.

How Moonlighting Affects Your IDR Payments

If you are on an income-driven repayment plan for your student loans, moonlighting income will increase your adjusted gross income and may raise your monthly payment at the next annual recertification. How much it increases your payment depends on the specific plan and your total income. Under SAVE, payments are generally 5 to 10 percent of discretionary income, so an additional $20,000 in moonlighting income might add $80 to $150 per month to your payment.

If you are pursuing PSLF, be aware that moonlighting at a for-profit facility does not jeopardize your PSLF eligibility as long as it is a secondary employer and your primary employment remains qualifying. However, the increased IDR payment from the additional income means you will pay slightly more toward your loans before forgiveness. For most residents, the net financial benefit of moonlighting still outweighs the marginal increase in loan payments - but it is worth running the numbers before committing to a heavy moonlighting schedule.