Does paying the safe harbor mean I owe nothing in April?

No. It only means there is no underpayment penalty. The rest of the tax is still due with the return.

Is the penalty worked out per quarter?

Yes. Each installment is compared with what was due by its date, and the penalty runs like interest on the shortfall from the due date until it is paid. Paying late is cheaper than not paying.

Federal estimated tax · 2026

Estimated tax safe harbor: which one is lower

Enter last year's total tax and AGI along with this year's figures. The planner compares 90% of the 2026 tax with 100% or 110% of the 2025 tax and builds the payment plan on the lower one.

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Filing▾

Tax yearFiling statusAged 65 or olderBlind

Income for the year▾

Self-employment profit

Net profit after business expenses (Schedule C)W-2 wages

Interest, ordinary dividends, rents

Not including qualified dividendsQualified dividends

Net long-term capital gain

A net loss counts up to $3,000Other taxable income

Retirement distributions, unemployment, short-term gains

Adjustments and deductions▾

Self-employed health insurance

SEP, SIMPLE, solo 401(k), IRA

Other adjustments

HSA, student loan interest, educator expensesItemized deductions

Used only if larger than the standard deduction

Business (QBI deduction)▾

Specified service business (consulting, law, accounting, health, financial services, performing arts, athletics). Matters only above $201,750 of taxable income ($403,500 joint).W-2 wages paid by the business

Qualified property (UBIA)

Dependents and credits▾

Children under 17Other dependentsOther nonrefundable credits

Education, child care, energy credits

Withholding and last year▾

Federal tax withheld this year

Expected total for the year, from pay stubs and 1099s

Last year's total tax

Form 1040 line 24, less refundable creditsLast year's AGI

Form 1040 line 11; over $150,000 means 110%

Estimated payments

None needed

Withholding covers the tax to within $1,000.

Due	Paid	Amount
Q1 April 15, 2026		—
Q2 June 15, 2026		—
Q3 September 15, 2026		—
Q4 January 15, 2027		—

Total income: $0
Adjusted gross income: $0
Standard deduction: −$16,100
Taxable income: $0
Income tax: $0
Total federal tax: $0
Effective rate · top bracket: 0% · 10%

Without last year's tax, the safe harbor is 90% of this year's tax. Enter last year's total tax to see whether paying 100% (or 110%) of it is lower.
The tax left after withholding is under $1,000, so no estimated payments are required for this year.

The three percentages

The penalty for underpaying estimated tax does not apply if withholding and timely estimated payments reach the smaller of 90% of this year's tax and 100% of last year's. If last year's adjusted gross income was over $150,000 ($75,000 married filing separately), the prior-year figure is 110%. The prior-year rule only works if last year's return covered all 12 months.

Which one to use

When income rises, the prior-year safe harbor is usually lower and fixed from the start of the year, so payments can be planned in January. When income falls, 90% of this year's tax is lower, but it depends on an estimate that can turn out wrong. The planner shows both and uses the lower.

Last year's total tax

Use the total tax on last year's Form 1040 (line 24) less refundable credits such as the additional child tax credit and the refundable part of the premium tax credit. That is the figure Form 2210 compares against.

Pricing

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✓2026 federal figures from the IRS
✓Self-employment tax and QBI deduction
✓90% / 100% / 110% safe harbor
✓Payment letters and CSV schedule (paid plans)
✓Calendar file with all four due dates
✓Client figures stay in your browser

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Questions

Does paying the safe harbor mean I owe nothing in April?: No. It only means there is no underpayment penalty. The rest of the tax is still due with the return.
Is the penalty worked out per quarter?: Yes. Each installment is compared with what was due by its date, and the penalty runs like interest on the shortfall from the due date until it is paid. Paying late is cheaper than not paying.