How does the formula work for married borrowers? Your spouse’s income is included in calculating monthly payments even if you file separate tax returns. However, a borrower may request that only his/her income be included if the borrower certifies that s/he is separated from his/her spouse or is unable to reasonably access the spouse’s income information. (See Section 4 of the IDR application and recertification form).
http://www.studentloanborrowerassistance.org/repayment/federal-loans/payment-plans/income-based-opti...
