Safe-harbor planning
Tax Underpayment Penalty Calculator
Estimate whether your federal withholding and estimated payments are tracking common IRS safe-harbor benchmarks before a year-end tax surprise.
Safe harbor in plain English
A safe harbor can protect you from an estimated-tax underpayment penalty when your timely payments meet an applicable benchmark. Common tests use 90% of current-year tax or 100% of prior-year tax; some higher-income taxpayers use 110% of prior-year tax. The exact result depends on your facts and the current IRS rules.
Balance due versus penalty
You can owe money when you file and still avoid an underpayment penalty if you met a safe harbor. Conversely, a taxpayer can have a smaller balance due but still need to review payment timing. Withholding is generally treated as paid throughout the year, while estimated payments are tied to their payment dates.
What to gather for an estimate
- Prior-year total tax and, when relevant, prior-year adjusted gross income.
- Current-year projected income, deductions, credits, and tax.
- Federal withholding from every paycheck, bonus, pension, or W-2.
- Dates and amounts of estimated tax payments.
Run your safe-harbor review
Compare projected tax, withholding, and payment targets, then get a W-4 adjustment suggestion.
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