In Schweiker v. Hansen (1981) 450 U.S. 785, the court concluded equitable estoppel is also unavailable to one who is procedurally ineligible. The respondent had met with a Social Security Administration field representative regarding her eligibility for "mother's insurance benefits" and was informed she was not eligible and need not file a claim. She later learned she was eligible, filed a claim, and began receiving benefits. When the respondent sought retroactive benefits due to the erroneous advice, the United States Supreme Court concluded equitable estoppel is unavailable. ( Id. at pp. 786-787.) The court explained: "Congress expressly provided in the Act that only one who 'has filed application' for benefits may receive them, and it delegated to petitioner the task of providing by regulation the requisite manner of application. A court is no more authorized to overlook the valid regulation requiring that applications be in writing than it is to overlook any other valid requirement for the receipt of benefits." ( Schweiker v. Hansen, supra, 450 U.S. at p. 790.)