Tax Extension & Late Penalty Calculator
See the dollar cost of filing or paying late — and the savings from filing a timely Form 4868 extension.
These are estimates. Want real numbers from a real CPA?
Real fee benchmarks for tax prep, bookkeeping, payroll, and advisory — by service and business type.
How it works
- Failure-to-file: 5% per month (or part), capped at 25% — waived if you filed Form 4868 on time and file by Oct 15.
- Failure-to-pay: 0.5% per month, capped at 25%; reduces the failure-to-file rate during overlapping months.
- Interest: IRS short-term federal rate + 3%, compounded daily (entered as a single annualized rate here).
Assumptions
- Federal individual return (Form 1040). State penalties differ.
- Doesn't model the minimum failure-to-file penalty when more than 60 days late.
- Interest rate is editable — check the current IRS quarterly rate.
Frequently asked questions
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These calculators provide estimates for general planning only and are not tax, legal, or financial advice. Always verify with a licensed CPA for your specific situation.
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