Free 1099 Self-Employed Tax Estimator — 2026 IRS Rules

The IRS Safe Harbor rule protects you from underpayment penalties if you pay at least 90% of your current year tax, or 100% of last year's tax (110% if AGI exceeds $150,000). Quarterly estimated payments are due April 15, June 15, September 15, and January 15 of the following year.

The IRS charges interest on underpaid amounts from each quarterly due date. The 2026 underpayment rate is based on the federal short-term rate plus 3 percentage points, updated quarterly. This calculator estimates penalties using the current IRS formula (Form 2210).

If you expect to owe $1,000 or more in taxes after subtracting withholding and credits, the IRS generally requires quarterly estimated payments. Failing to pay on time can result in penalties even if you pay in full by April 15.

The simplified method gives you $5/sq ft (max $1,500). The actual expense method lets you deduct a percentage of real costs (mortgage interest, utilities, repairs, insurance) based on the square footage percentage of your home used for business. You can choose either method each year — pick whichever gives you the larger deduction.

No. In most cases, you must choose either the standard mileage rate OR actual expenses for a given vehicle. If you use the standard mileage rate in the first year the vehicle is used for business, you can switch to actual expenses in later years. If you start with actual expenses, you cannot switch to standard mileage later.

Above-the-line deductions reduce your Adjusted Gross Income (AGI) before you choose between standard and itemized deductions. This is powerful because you get the benefit regardless of whether you itemize. Other above-the-line deductions include SE tax deduction (50%), SEP IRA contributions, and student loan interest.

Generally, no. If you are eligible to participate in a subsidized employer health plan (yours or your spouse's), you cannot claim the self-employed health insurance deduction for those months. This is a common IRS audit trigger — be careful.

S-Corp election typically saves money when net profit exceeds ~$60,000-$80,000. Below that, the added costs of payroll, tax filings (Form 1120-S), state S-Corp fees, and unemployment insurance often outweigh SE tax savings. This calculator shows you the tax difference — but factor in $1,000-$3,000/year in additional admin costs.

The "reasonable salary" requirement is the #1 IRS audit trigger for S-Corps. If the IRS determines your salary was unreasonably low (to avoid payroll taxes), they can reclassify distributions as wages and assess back taxes, penalties, and interest — sometimes going back multiple years.

All your saved scenarios, income data, and calculation results are stored exclusively in your browser's localStorage. Nothing is sent to any server. If you clear your browser data or use a different device, your saved scenarios will not be available. Export CSV to back up your data.

Currently, you can save new scenarios and delete old ones. To update a scenario, delete the old entry and save a new one with the same name. This simple approach keeps your data under your control without complex editing features that might cause data loss.

Most states offer a credit for taxes paid to other states on the same income, preventing double taxation. For example, if you live in California but earned income in New York, you can claim a credit on your CA return for NY taxes paid on that income. Rules vary by state.

Generally, yes — if you earned income in a state with income tax, you likely need to file a non-resident return in that state, even if you only worked there for a short period. Each state has its own filing thresholds. Some states have reciprocity agreements with neighboring states.

The $400 threshold applies to NET self-employment earnings (gross income minus deductible business expenses). If your net earnings are $400 or more, you must file Schedule SE and pay self-employment tax, even if your total income is below the standard deduction and you owe zero federal income tax.

If your net self-employment earnings are under $400, you generally do not owe self-employment tax. However, you may still need to file a tax return if your total income (from all sources) exceeds the standard deduction for your filing status. You must also report all income regardless of amount if required to file for other reasons.

The IRS distinguishes between a hobby and a business. If your activity is not engaged in for profit, it may be classified as a hobby. Hobby income must still be reported, but hobby expenses are no longer deductible under the Tax Cuts and Jobs Act. The "3-of-5-year profit" test is a key factor in determining business vs. hobby status.

A SEP IRA is simpler — all contributions are employer-side (up to 25% of net earnings, max $70,000 in 2026). A Solo 401(k) allows BOTH employee deferrals (up to $23,500 in 2026, plus $7,500 catch-up if 50+) AND employer profit-sharing contributions (up to 25% of net earnings), with a combined max of $70,000. Solo 401(k) generally allows higher contributions at lower income levels and also allows Roth contributions and loans.

Traditional (pre-tax) SEP IRA and Solo 401(k) contributions are deducted from your taxable income, reducing both federal income tax and (in most states) state income tax. For example, if you contribute $20,000 and are in the 24% federal bracket, you save approximately $4,800 in federal taxes. Contributions still reduce SE tax? No — retirement contributions only reduce income tax, not self-employment tax (Social Security + Medicare).

Both SEP IRA and Solo 401(k) contributions can be made up to the tax filing deadline (including extensions) — typically April 15 of the following year, or October 15 with an extension. However, the Solo 401(k) plan itself must be established by December 31 of the tax year (SEP IRA can be set up by the filing deadline).