Back Taxes Calculator 2026 β IRS Penalties & Interest by Year
Calculate exactly how much you owe the IRS for unfiled or unpaid prior year taxes. See failure-to-file penalties, failure-to-pay penalties, and compounded daily interest for each year.
Unfiled Tax Years
Today's date: |
Interest rate used: 7.0% annually (7% = federal short-term + 3%)
$0
Grand Total Owed
$0
Original Tax Debt
$0
Total FTF Penalties
$0
Total FTP Penalties
$0
Total Interest
0%
Penalties & Interest as % of Debt
Per-Year Breakdown
| Tax Year | Original Tax | FTF Penalty | FTP Penalty | Interest | Total Owed |
|---|---|---|---|---|---|
| Total |
How to Use This Back Taxes Calculator
Click "+ Add Year" for each year you have unpaid taxes. Enter the original tax owed for each year. The due date auto-fills to April 15 of the following year (e.g., 2022 taxes are due April 15, 2023). The calculator computes all penalties and interest from the due date to today.
The Formula
Months late = floor((today β due_date) / 30)
FTF penalty months = min(months_late, 5) [caps at 25%]
FTF penalty = original_tax Γ min(months_late Γ 4.5%, 22.5%)
FTP penalty = original_tax Γ min(months_late Γ 0.5%, 25%)
Interest = original_tax Γ [(1 + 0.07/365)^days_late β 1]
Interest also applies to accumulated penalties
Total per year = Original + FTF + FTP + Interest
FTF penalty months = min(months_late, 5) [caps at 25%]
FTF penalty = original_tax Γ min(months_late Γ 4.5%, 22.5%)
FTP penalty = original_tax Γ min(months_late Γ 0.5%, 25%)
Interest = original_tax Γ [(1 + 0.07/365)^days_late β 1]
Interest also applies to accumulated penalties
Total per year = Original + FTF + FTP + Interest
Example
2021 taxes: $10,000 owed, due April 15, 2022 (about 3 years late):
FTF penalty: $10,000 Γ 22.5% (5 months max) = $2,250
FTP penalty: $10,000 Γ 18% (36 months Γ 0.5%) = $1,800
Interest: $10,000 Γ [(1.07/365)^1095 β 1] β $2,252
Total owed: ~$16,302 (63% more than original)
FTF penalty: $10,000 Γ 22.5% (5 months max) = $2,250
FTP penalty: $10,000 Γ 18% (36 months Γ 0.5%) = $1,800
Interest: $10,000 Γ [(1.07/365)^1095 β 1] β $2,252
Total owed: ~$16,302 (63% more than original)
Filing Late Is Always Better Than Not Filing
- The FTF penalty (4.5%/month) is 9x worse than the FTP penalty (0.5%/month)
- File even if you cannot pay β this immediately reduces your accruing penalties
- Request an extension before the due date to avoid the FTF penalty entirely
- Apply for First-Time Penalty Abatement after filing β penalties can be removed, interest cannot
Extended
Resolution Options Comparison
Compare your options: pay in full, installment agreement, OIC estimate, and currently not collectible
Resolution Options Comparison
Compare the four main strategies for resolving your total back tax balance.
Frequently Asked Questions
What is the failure-to-file penalty and how is it calculated?
The failure-to-file (FTF) penalty is 5% of unpaid taxes per month (or partial month) you are late filing your return, up to a maximum of 25% of your unpaid taxes. However, when both failure-to-file and failure-to-pay apply, the combined rate is 5% per month: 4.5% failure-to-file plus 0.5% failure-to-pay. After 5 months, the FTF penalty caps at 25%, but the FTP penalty continues at 0.5% per month until it too reaches 25%.
What is the failure-to-pay penalty?
The failure-to-pay (FTP) penalty is 0.5% of unpaid taxes per month (or partial month) you owe a balance, capped at 25%. If you have an installment agreement in place, the rate drops to 0.25% per month. Unlike the failure-to-file penalty, the FTP penalty continues until the debt is fully paid or reaches the 25% maximum, which takes approximately 50 months.
How does IRS interest on back taxes work?
IRS interest compounds daily on any unpaid tax balance, including unpaid penalties. The rate is the federal short-term rate plus 3%, recalculated quarterly. For 2024-2026, this is approximately 7% annually. Interest cannot be abated β only penalties can be reduced through abatement. This is why even small tax debts grow significantly over several years.
Is there a statute of limitations on IRS back taxes?
The IRS generally has 10 years from the date of assessment to collect a tax debt β this is the Collection Statute Expiration Date (CSED). However, certain events toll (pause) the clock, including pending OIC applications, installment agreement requests, and bankruptcy filings. The 3-year statute of limitations on audits starts when you file, so unfiled returns have no statute running at all.
Can the IRS waive penalties on back taxes?
Yes. The IRS offers First-Time Penalty Abatement (FTA) if you have a clean compliance history (no penalties in the prior 3 years, all returns filed, no current payment plan debt). You can also request Reasonable Cause abatement for serious illness, natural disaster, death in the family, or IRS error. Interest cannot be abated except in very narrow circumstances such as IRS errors. Applying for abatement after paying the debt can result in a refund.