See what an IRS installment agreement really costs — the monthly payment plus the failure-to-pay, failure-to-file and interest charges that run on top of the tax you owe.
| Balance | Plan Length | Plan Type | Failure-to-Pay | Failure-to-File | Interest | Total Extra | Monthly |
|---|---|---|---|---|---|---|---|
| $12,000 | 6 mo | Short, no fee | $360 | $0 | $254 | $614 | $2,102 |
| $12,000 | 12 mo | Long-term | $720 | $0 | $489 | $1,240 | $1,103 |
| $25,000 | 24 mo | Long-term, filed 6 mo late | $3,000 | $5,625 | $2,509 | $11,165 | $1,507 |
| $45,000 | 36 mo | Long-term, $5,000 already paid | $7,200 | $0 | $5,270 | $12,501 | $1,458 |
Every figure above comes from the same arithmetic the calculator runs: the failure-to-pay penalty is 0.5% of the balance per month capped at 25%, the failure-to-file penalty adds 4.5% per month for up to five months when it runs alongside the failure-to-pay penalty, and interest compounds monthly at the 7% underpayment rate. Note the last row: paying $5,000 up front removes it from the penalty base, which is why the penalty drops even though the plan is longer than the row above.
| Penalty | Rate | Maximum | Applies when |
|---|---|---|---|
| Failure to pay (IRC 6651(a)(2)) | 0.5% per month | 25% | Tax shown on a filed return is not paid |
| Failure to file (IRC 6651(a)(1)) | 5% per month | 25% | Return is filed after the due date |
| Both running together | 4.5% + 0.5% = 5% per month | 25% each | Late return with unpaid tax |
| Interest (IRC 6601) | Federal short-term rate + 3% | None | From the original due date |
The 5%-per-month failure-to-file penalty is reduced by the failure-to-pay penalty for any month both apply, which is why the combined figure is 4.5% + 0.5% rather than 5.5%. Filing the return even when you cannot pay is worth far more than the cost of paying late: the failure-to-file penalty is ten times the failure-to-pay rate.
If the balance is under about $10,000 and you can borrow at a rate below the IRS underpayment rate, a personal loan or a 0% purchase card is usually cheaper than a long-term plan, because you avoid the 0.5% monthly penalty entirely. A plan makes sense when the balance is large, you cannot get credit, or you need the collection hold that an agreement provides.
An IRS payment plan solves a cash-flow problem, not a tax problem. The balance still carries the failure-to-pay penalty of 0.5% per month, and interest accrues on both the tax and the penalty. Over two years those charges typically add 12% to 20% to what you owe — on a $25,000 balance with a late return, our example pays $11,165 on top of the tax itself.
The calculator separates four costs so you can attack them in the right order. The balance is what penalties are charged on, so any down payment cuts every later charge. The setup fee is fixed and avoidable if you finish inside 180 days. The penalties are the expensive part at 0.5% or 5% per month. Interest is the cheapest component and the one most people fixate on. Paying down the balance early always beats shortening the plan.
Apply online through the IRS Online Payment Agreement tool, which gives instant approval for balances under $50,000 if you have filed all required returns. Set up direct debit — it cuts the fee to $31 and the IRS treats a missed direct-debit payment less harshly than a missed manual one. Then keep filing on time every year: a new unfiled return can default an existing agreement even if you never miss a payment.
⚠️ Important: An IRS payment plan does not stop penalties or interest, and a missed payment can default the agreement and trigger a levy. This calculator uses a 7% annual underpayment rate for illustration; the IRS updates its quarterly rate, and the failure-to-file penalty applies only if your return was actually filed late. Confirm your exact balance with the IRS before relying on these figures.