Income-Based Repayment (IBR)
If you’re enrolled in the IBR plan, your monthly payment amount will be limited to 15% of your discretionary income. You’ll also have to recertify your income and family size each year.
If you do those things and still have a remaining balance at the end of 25 years, regardless of what type of federal student loans you have (with the exception of Federal PLUS loans made to parents), you will be forgiven.
Income-Contingent Repayment (ICR) plan
If you’re enrolled in ICR, you’ll have the highest monthly payments of all: either 20% of your discretionary income or whatever the payment would be on a 12-year repayment plan (whichever is less). You’ll also need to recertify your income and family size with this plan as well.
ICR also has one of the longest repayment periods. If you have anything left on your student loan balance after 25 years, it’ll be forgiven.
Perkins loans work a bit differently the most other federal loans. Rather than being doled out through the William D. Ford Direct Loan program as with most federal student loans, each loan is made directly to you from the school itself. That means that when it comes time to apply for forgiveness, you’ll need to contact the school itself for an application.