Last Fall the rules for Income Based Repayment (IBR) changed.
Approximately every twelve months the servicing provider for your Direct Loans will send you a notification with a time-sensitive request to submit either your most recent tax return (1040, 1040 A or 1040 EZ) or an Alternate Documentation Form along with proof of you current income. In order to keep your IBR enrollment active you must respond within 30 days of the date of the letter. If the requested documents are not received within those 30 days, your loans will default into the 10-year repayment schedule.
Please make sure your lender always has your current address and that you read all correspondence.