The IRS charges interest on unpaid taxes, and that interest keeps growing while you're on a payment plan
When you set up a payment plan with the IRS, you're not just paying back the tax you owe. You're also paying interest on that unpaid balance, calculated daily. The interest rate is set by federal law and changes every quarter — it's always the federal short-term rate plus 3 percentage points. As of early 2024, that rate is around 8 percent per year, but the exact number depends on which quarter your plan starts and how long you keep it active.
The IRS also charges a failure-to-pay penalty on top of the interest — usually 0.5 percent of what you owe each month, up to 25 percent total. Both the interest and the penalty are added to your balance every day, which means the longer your plan runs, the more you'll owe overall. Understanding how these charges work helps you decide whether to pay faster, make a lump-sum payment when you can, or explore other options.
Key Takeaways
- The IRS interest rate changes every quarter and is currently around 8 percent per year, but you can find the exact rate for your quarter on the IRS website or in your payment plan agreement.
- Interest is calculated daily on your unpaid balance, so the longer your plan runs, the more total interest you'll pay.
- A failure-to-pay penalty of 0.5 percent per month is added on top of interest, and both charges compound as your balance grows.
- Making extra payments toward principal reduces the amount interest is calculated on, so paying more than your monthly plan amount saves money over time.
- Short-term plans (under 120 days) have lower setup fees and may accrue less total interest than longer arrangements.
How the quarterly interest rate is set and where to find yours
The IRS publishes a new interest rate every three months: January, April, July, and October. The rate is the federal short-term rate (set by the Treasury Department) plus 3 percentage points, rounded up to the nearest whole percent. This means the rate can change when your plan crosses into a new quarter, even if you're already making payments.
You can find the current and past rates on the IRS website under "Interest Rates" or in the Notice 746 that the IRS publishes each quarter. Your payment plan agreement will also state the rate that applies to your plan at the time you set it up. If you want to know the exact rate for your specific situation, call the IRS at 1-800-829-1040 or check your online account through IRS.gov if you have one set up.
Why interest and penalties keep growing on a payment plan
The IRS calculates interest daily, not monthly or annually. This means interest accrues on your unpaid balance every single day you're on the plan. If your plan runs for three years, you're paying interest for 1,095 days, and that compounds — interest is charged on the interest you've already accrued.
The failure-to-pay penalty works separately. It's 0.5 percent of your unpaid tax per month (or part of a month), up to a maximum of 25 percent. This penalty is reduced to 0.25 percent per month if you're on an installment plan and making payments on time. The penalty stops accruing once you've paid everything off, but it continues to grow while you're behind, even if you're making regular plan payments.
Together, interest and penalties can add 30 to 50 percent to your original tax bill over a multi-year plan. This is why the IRS encourages people to pay as quickly as possible and why making extra payments toward principal — beyond what your plan requires — saves significant money.
The difference between short-term and long-term payment plans
The IRS offers two main types of payment plans: short-term (under 120 days) and long-term (installment agreements). Short-term plans have no setup fee, while long-term plans charge a fee of $31 to $225 depending on how you pay and your income level. The longer your plan, the more total interest you'll pay because interest accrues every day.
A short-term plan might cost you less in total interest, but it requires larger monthly payments. A long-term plan spreads payments over months or years, which lowers each payment but increases the total interest bill. For example, owing $5,000 with interest at 8 percent annually costs roughly $400 in interest over one year, but $1,200 over three years. Your choice depends on whether you can afford higher monthly payments to reduce the total cost.
How to reduce the interest you pay on your plan
The most direct way to reduce interest is to pay off your balance faster. Every dollar you pay toward principal reduces the amount that interest is calculated on going forward. If your plan requires $200 per month but you can pay $300, that extra $100 goes directly to principal and saves you interest on future months.
You can also make a lump-sum payment whenever you have the money — a tax refund, bonus, or inheritance. The IRS applies lump-sum payments to your balance when ready, and interest stops accruing on that portion. There's no penalty for paying off your plan early, and you won't owe any remaining setup fees.
Another option is to request a short-term plan if you can pay within 120 days. Short-term plans have no setup fee and accrue less total interest because the repayment period is shorter. If you can't pay within 120 days, ask whether a 12-month plan (instead of 24 or 36 months) is affordable — the shorter the plan, the less interest you'll owe overall.
What happens to interest if you miss a payment
If you miss a payment on your plan, the IRS doesn't when ready cancel it, but interest and penalties continue to accrue on your unpaid balance. The failure-to-pay penalty may increase if you fall behind, and the IRS may send you a notice. If you miss payments for several months, the IRS can terminate your plan and demand full payment of the remaining balance when ready.
If you know you'll miss a payment, contact the IRS before the due date. You may be able to adjust your plan, skip a month, or extend the timeline. It's better to ask for a change than to miss a payment and let penalties grow. Call 1-800-829-1040 or log into your IRS account online to request a modification.
Interest rates across different payment plan types
| Plan Type | Interest Rate | Setup Fee | When to Use |
|---|---|---|---|
| Short-term (under 120 days) | Current quarterly rate (~8%) | None | You can pay within four months |
| Long-term installment (12–84 months) | Current quarterly rate (~8%) | $31–$225 | You need 1–7 years to pay |
| Automated payment (direct debit) | Current quarterly rate (~8%) | $31 (lower than other methods) | You want the lowest setup fee |
Frequently Asked Questions
Can I negotiate the interest rate on my payment plan?
No. The interest rate is set by federal law and applies to all taxpayers. You cannot negotiate it down, but you can reduce the total interest you pay by paying off your plan faster or making extra payments toward principal.
Does the interest rate change while I'm on a payment plan?
Yes. The IRS interest rate changes every quarter (January, April, July, October). If you're on a long-term plan, your rate may increase or decrease when the quarter changes. The IRS will notify you of any rate change, and your new rate applies to the unpaid balance going forward.
What's the difference between interest and the failure-to-pay penalty?
Interest is the cost of borrowing money from the IRS, calculated daily at the quarterly rate. The failure-to-pay penalty is an additional charge of 0.5 percent per month (or 0.25 percent if you're on a plan and paying on time). Both are added to your balance and compound over time.
If I pay off my plan early, do I owe all the interest upfront?
No. Interest accrues only on the days your balance is unpaid. If you pay off your plan in six months instead of 36 months, you pay interest for six months, not three years. The IRS stops charging interest the day your balance reaches zero.
How much total interest will I pay on a three-year plan?
It depends on how much you owe and the interest rate during your plan period. As a rough estimate, at 8 percent annual interest, you'll pay about 24 percent of your original tax amount in interest over three years. The exact amount varies based on quarterly rate changes and whether you make extra payments.