5% of Discretionary Income: How the SAVE Plan Calculates Monthly Payments and Forgiveness

On July 10, 2023, the U.S. Department of Education published a final rule in the Federal Register that fundamentally altered the mathematics of federal student loan repayment. The Saving on a Valuable Education (SAVE) plan changed two specific variables in the government's formula: it increased the amount of income shielded from assessment from 150% to 225% of the Federal Poverty Line, and it halved the payment rate on undergraduate debt from 10% to 5%. For a single borrower earning $50,000, those two adjustments drop an annual payment obligation from approximately $2,813 under legacy plans to just $860.[1][3]

To understand how the formula works, it is necessary to understand how the federal government calculates affordability. Unlike a standard private mortgage or auto loan, which divides the principal and interest into fixed monthly installments over a set term, federal income-driven repayment (IDR) plans ignore the total balance. Instead, they calculate a monthly bill based entirely on what the borrower earns and the size of their household, ensuring that payments scale with the borrower's ability to pay.[1][4]

The foundation of this calculation is "discretionary income"—the money a borrower has left over after accounting for basic living expenses. Under legacy IDR plans like Revised Pay As You Earn (REPAYE), the Department of Education defined basic living expenses as 150% of the Federal Poverty Line. The SAVE plan pushed that protective shield to 225%, exempting a significantly larger portion of a borrower's paycheck from the government's reach.[1][5]

In practical terms, using the 2023 poverty guidelines active when the rule was finalized, that shift moved the protected income floor for a single borrower in the contiguous United States from roughly $21,870 to $32,805. For a family of four, the protected floor rose to $67,500. If a borrower's Adjusted Gross Income falls below that 225% threshold, their calculated discretionary income is zero, which mathematically results in a $0 required monthly payment.[1][6]

Once the discretionary income is established, the formula applies an assessment rate to determine the actual bill. Legacy plans universally charged 10% of that remaining income across all loan types. The SAVE plan introduced a bifurcated rate based on the educational credential the debt financed. Undergraduate loans are assessed at 5% of discretionary income, effectively cutting the out-of-pocket obligation in half for borrowers with bachelor's or associate degrees.[1][2]

Graduate loans, however, remain assessed at the historical 10% rate. For borrowers holding a mix of both undergraduate and graduate debt, the Department of Education calculates a weighted average based on the original principal balances. If a borrower took out $20,000 for a bachelor's degree and $20,000 for a master's degree, their blended assessment rate is set at exactly 7.5% of their discretionary income.[1][5]

Beyond the monthly payment calculation, the SAVE plan overhauled how the federal ledger handles accumulating interest. Under previous IDR plans, a structural flaw known as negative amortization trapped many lower-income borrowers. If a borrower's calculated monthly payment was lower than the interest accumulating on their loan that month, the unpaid interest was added to the total balance. Consequently, borrowers could make every required payment for a decade and still owe more than they originally borrowed.[3][6]

The SAVE plan eliminated negative amortization by introducing a 100% interest subsidy. Under this mechanism, the government forgives any unpaid interest remaining after a borrower makes their calculated monthly payment. If a borrower's loan accrues $50 in interest in a given month, but their income dictates a $10 SAVE payment, the remaining $40 is subsidized by the Department of Education. As long as the borrower makes the $10 payment, their principal balance remains entirely flat.[1][5]

The final mathematical component of the SAVE plan is its accelerated timeline for loan forgiveness. Standard income-driven plans require borrowers to make qualifying payments for 20 or 25 years before the government forgives the remaining balance. The SAVE formula introduced a sliding scale tied directly to the original principal amount borrowed, designed specifically to clear the debt of community college students and those who did not complete their degrees.[1][4]

Under this sliding scale, borrowers who took out $12,000 or less in total federal loans receive full forgiveness after 10 years, or 120 monthly payments. For every additional $1,000 borrowed above that $12,000 baseline, the timeline extends by one year. A borrower who originally took out $14,000 reaches forgiveness in 12 years. The scale caps at 20 years for undergraduate-only borrowers and 25 years for those with graduate loans.[1][6]

While the mathematics of the SAVE plan represent the most generous federal lending formula ever published, the implementation of these rules is currently halted. Following a prolonged legal battle over executive authority, the program was struck down. "On March 10, 2026, a federal court issued an order preventing the U.S. Department of Education (ED) from implementing the SAVE Plan and parts of other income-driven repayment (IDR) plans," the agency noted in its guidance to borrowers.[2][4]

As a result of that ruling, the 225% poverty shield, the 5% undergraduate rate, and the 100% interest subsidy are no longer active. The Department of Education placed enrolled borrowers into an interest-free forbearance while unwinding the program. To resume making progress toward the standard 20- or 25-year forgiveness timelines, borrowers must now submit applications to transition back to legacy plans like Income-Based Repayment (IBR) or Pay As You Earn (PAYE), which calculate payments using the older, more expensive formulas.[2][5]