What Income-Based Repayment (IBR) Actually Calculates

Income-Based Repayment is a federal student loan repayment plan that sets your monthly payment based on your income and family size, not on how much you borrowed. The Department of Education uses a formula that takes your discretionary income—what's left after they subtract a percentage of the federal poverty line from your gross income—and divides it by 240 months (20 years). That quotient is your payment.

The formula does not look at your loan balance, interest rate, or how many loans you have. It only looks at income. This means two borrowers with identical loans can have completely different payments if their incomes differ. It also means your payment can be as low as $0 per month if your income falls below the poverty threshold for your family size.

IBR is one of four income-driven plans available to federal student loan borrowers. The others are PAYE (Pay As You Earn), REPAYE (Revised Pay As You Earn), and ICR (Income-Contingent Repayment). Each uses a slightly different formula and has different rules about interest accrual and forgiveness. This guide covers IBR specifically.

Key Takeaways

  • IBR divides your discretionary income by 240 months; discretionary income is your gross income minus 150% of the federal poverty line for your family size.
  • You must recertify your income every year, and your payment can change if your income or family size changes.
  • If your payment does not cover accrued interest, the unpaid interest capitalizes (gets added to your principal) after three years, unless you are on PAYE.
  • The Federal Student Aid website has a Loan Simulator tool where you can enter your income and see your estimated payment before you commit to the plan.
  • After 20 years of may have access to payments under IBR, any remaining balance is forgiven, though forgiveness may trigger a tax bill.

The Discretionary Income Formula

Discretionary income is the number the IBR formula actually uses. It is calculated as: your Adjusted Gross Income (AGI) minus 150% of the federal poverty line for your family size and state.

The federal poverty line changes every year. For 2024, the poverty line for a single person is approximately $14,600, so 150% of that is $21,900. For a family of four, the poverty line is approximately $30,000, so 150% is $45,000. The Department of Education publishes updated poverty guidelines each year, usually in January.

If your AGI is $35,000 and you are single, your discretionary income is $35,000 minus $21,900 = $13,100. If your discretionary income is negative (your income is below the poverty threshold), your IBR payment is $0, but you still must recertify your income annually to stay on the plan.

Your AGI comes from your most recent tax return. If you are married filing jointly, you use the joint AGI. If you are married filing separately, you use only your own income. If you have not filed taxes yet, you can use an estimate, but you will need to update it once you file.

Dividing Discretionary Income by 240 Months

Once you have your discretionary income, divide it by 240. That is your monthly IBR payment.

Using the example above: $13,100 discretionary income ÷ 240 months = $54.58 per month. The Department of Education rounds to the nearest dollar, so your payment would be $55.

This payment is fixed for one year. After 12 months, you must recertify your income. If your income has changed, your discretionary income changes, and so does your payment. If your income has stayed the same, your payment stays the same.

The 240-month clock does not reset when you recertify. If you have been on IBR for 8 years and recertify, you still have 12 years left before forgiveness. The clock only resets if you switch to a different repayment plan and then switch back to IBR.

How to Use the Federal Student Aid Loan Simulator

The fastest way to see your estimated IBR payment without doing the math yourself is the Loan Simulator on studentaid.gov. You enter your income, family size, state, and loan balances, and it shows you what your payment would be under each income-driven plan.

To use it: go to studentaid.gov, search for "Loan Simulator," and select the tool. You will need your most recent tax return or an income estimate. The tool does not save your information or connect to your actual loan account; it is purely for estimation.

The simulator shows you not just your monthly payment, but also how much interest will accrue, how long it will take to pay off the loan, and what the forgiven amount might be. This is useful if you are deciding between IBR and another plan, because you can compare the total cost of each option.

Keep in mind the simulator uses current poverty guidelines and tax brackets. If your income or family size changes, your actual payment will change too. The tool is accurate for the year you run it, but you should recalculate if your circumstances shift significantly.

What Happens When Your Payment Does Not Cover Interest

If your IBR payment is low—because your income is low—it may not cover all the interest that accrues each month. When that happens, the unpaid interest does not disappear. Instead, it sits unpaid until one of three things occurs: you make a larger payment, your income rises and your payment rises, or three years pass.

After three years of payments where interest goes unpaid, the Department of Education adds that unpaid interest to your principal balance. This is called capitalization. Once interest capitalizes, you are paying interest on interest, which increases the total amount you owe.

There is one exception: if you are on PAYE (Pay As You Earn), unpaid interest does not capitalize while you are on the plan. If you switch to IBR from PAYE, capitalization rules change, so be aware of that if you are considering a switch.

To avoid capitalization, you can make extra payments toward principal whenever you can, or you can switch to a standard 10-year repayment plan if your income rises enough that you can afford it. Some borrowers stay on IBR specifically because the payment is manageable, even if it means interest capitalizes over time.

Recertifying Your Income Every Year

IBR requires you to recertify your income once per year. The Department of Education sends you a notice when recertification is due, usually 60 days before your anniversary date on the plan. You can recertify online through your loan servicer's website, by phone, by mail, or by fax.

When you recertify, you provide your current income (usually from your most recent tax return) and confirm your family size and state. If your income has not changed, your payment stays the same. If your income has risen, your payment rises. If your income has fallen, your payment falls.

If you miss your recertification deadline, your loan servicer will contact you. If you do not recertify within 120 days of the deadline, you will be moved off the income-driven plan and onto the standard 10-year repayment plan, which is usually much more expensive. To avoid this, set a calendar reminder when you receive the recertification notice.

If your income has changed significantly since your last tax return—you lost a job, got a raise, or had a major life change—you can request an out-of-cycle recertification. Your servicer will review the request and may move up your recertification date.

The 20-Year Forgiveness Timeline

After you have made 240 may have access to payments (20 years) under IBR, any remaining loan balance is forgiven. A may have access to payment is one you make on time, in the full amount due, while you are on IBR. Payments made under other plans do not count toward the 240.

The forgiveness happens automatically once you reach 240 payments. Your servicer will notify you, and the remaining balance will be discharged. However, the forgiven amount may be treated as taxable income by the IRS, which means you could owe federal income tax on it in the year of forgiveness.

For example, if you have $50,000 forgiven, the IRS may count that as $50,000 of income for that tax year. Depending on your tax bracket, you could owe several thousand dollars in taxes. Some borrowers set aside money during their repayment years to cover this potential tax bill. Others look into whether they may have access to for any tax exclusions (which are rare and narrow).

Frequently Asked Questions

What if I get married or have a child while on IBR?

Your family size changes, which changes your discretionary income calculation and your payment. You must recertify to update your family size. If you get married and file taxes jointly, your spouse's income counts toward your discretionary income (unless you file separately). A new child lowers your discretionary income because the poverty threshold rises, which usually lowers your payment.

Can I switch from IBR to another repayment plan?

Yes. You can switch to any other federal repayment plan at any time. If you switch away from IBR and then switch back later, the 240-month clock resets. This means if you were on IBR for 10 years, switched to standard repayment for 2 years, and switched back to IBR, you start the 20-year timer over. Plan switches carefully if you are close to forgiveness.

Do I have to be on IBR to get Public Service Loan Forgiveness?

No. Public Service Loan Forgiveness (PSLF) requires 120 may have access to payments while working full-time for a may have access to employer, but you can be on any repayment plan, including standard 10-year. However, being on IBR often means lower payments, so you may pay less total while waiting for PSLF forgiveness.

What if my income is zero or I am unemployed?

Your IBR payment will be $0 if your income is below 150% of the poverty line. You must still recertify annually to stay on the plan and keep your $0 payment status. Periods of $0 payment do count toward your 240 may have access to payments, so unemployment does not stop your progress toward forgiveness.

How do I know if IBR is better than PAYE or REPAYE?

The three plans use different formulas and have different rules about interest capitalization and forgiveness. PAYE caps your payment at 10% of discretionary income (IBR caps at 15%), but PAYE has stricter income and loan-age requirements. REPAYE has no income cap but counts spousal income even if you file separately. Use the Loan Simulator to compare your estimated payment and total cost under each plan.