Free moonlighting math · no account
Self-employment income is taxed differently than your W-2. See the take-home after SE tax, federal, and state — and the solo 401(k) room it opens. Nothing you enter is stored or shared.
Estimated at a 3.07% state marginal rate on the 1099 income.
Add your W-2 income and expected 1099 income above to see the take-home.
Estimates at the 2026 single-filer schedule; actual liability depends on filing status, deductions, and other income. Education, not advice — confirm quarterly estimates with your CPA. Also check your contract for moonlighting restrictions and confirm malpractice coverage for outside shifts before picking one up.
The math above is the short version. Moonlighting and 1099 Income — from the paycheck & lifestyle curriculum — covers the decisions behind it. Free to read.
Inputs
Assumptions
Formula
Stack the 1099 income on top of W-2 income, compute self-employment tax and the surtax, deduct half of SE tax, then take the federal and state tax on the marginal slice. Keep = 1099 income minus those taxes.
Result
What you keep from the 1099 income after the taxes it triggers, with each tax as its own line, and the quarterly estimated-tax calendar.
What isn’t included
Source and rule year
Rule year 2026 · figures and formulas re-verified September 2026 by Jonathan Shafer, DO · IRS Rev. Proc. 2025-32 — 2026 brackets · IRS Schedule SE · SSA — wage base · how our numbers are sourced. Education, not advice.
Three ways. First, nothing is withheld — the gross amount hits your bank account and the tax bill arrives later, which is why moonlighting income feels bigger than it is. Second, you owe self-employment tax: both the employee and employer halves of Social Security and Medicare, since no employer is paying the other half for you. Third, you are responsible for paying the tax through quarterly estimates rather than payroll withholding. The same dollar of income is real in both cases; the plumbing is entirely different.
Self-employment tax is Social Security and Medicare assessed on self-employment earnings: 12.4% for Social Security up to the annual wage base (your W-2 wages count against that base first) and 2.9% for Medicare on every dollar, plus a 0.9% additional Medicare surtax above the statutory threshold. Half of the self-employment tax is deductible above the line, which softens the federal income-tax bill but not the SE tax itself.
Usually, yes. The IRS expects tax to be paid as income is earned, and underpaying through the year draws a penalty even if you settle in full each April. The common physician-friendly alternative is increasing withholding on your W-2 paycheck to cover the moonlighting liability — withholding is treated as paid evenly through the year regardless of when it actually happens. Either route works; ignoring the liability until filing season is the expensive option.
Yes — self-employment income makes you an employer, and an employer can sponsor a retirement plan. As the employer you can contribute roughly 20% of net self-employment income for an unincorporated sole proprietor, and that room is in addition to the workplace 403(b) or 401(k) at your W-2 job. The employee deferral limit is shared across all your plans, but the employer side is not — which is why a moonlighting physician who already maxes a 403(b) can still shelter thousands more. The plan must be established by December 31 of the tax year.