on some of the refunds that Customs owed to Supermail. On October 25, 1989 and on December 14, 1989, the IRS issued notices of the levies to Customs. Both notices specifically stated: “This levy attaches to refunds due Supermail Cargo Inc.”
Neither the IRS nor Customs informed Supermail (or for that matter Mandel, Resti) of the levies. Only the Customs Service received the IRS notices. Supermail, which had a number of protests pending, continued to inquire unsuccessfully of Customs about the status of its refunds. Over two years after the levies were made, Customs incorrectly informed Supermail that the refunds had been delayed inadvertently but would eventually be paid. Two weeks later, on February 24, 1992, Customs finally advised Supermail that the IRS had levied on its refunds and, therefore, that Supermail would not receive them after all.
On June 9, 1992, Supermail filed a request for the return of its property with the New York IRS office. The IRS initially ignored it. Later, when Supermail inquired as to the status of the request, the acting manager of the New York IRS office asked that additional information be submitted. Supermail promptly complied. However, on October 21, 1992, the acting manager of the New York office informed Supermail that it must file its request with the Fresno, California IRS office. Again, Supermail promptly complied with the IRS’s instructions by filing a request for the return of its property with that office on October 29, 1992.
For the next several months, the IRS failed to issue a decision. On April 8, 1993, Supermail again wrote to the IRS, threatening to file a civil action unless the IRS responded to its request. The IRS, told Super-mail that it would act on its request if additional information were provided. Yet again, Supermail promptly complied, forwarding the requested information to the Los Angeles, California IRS office. Finally, on July 26, 1993, the Los Angeles, California IRS office denied Supermail’s request for the return of its property on the ground that the request had not been timely filed.1
On October 8, 1993, Supermail filed this action in federal district court under 26 U.S.C. § 7426, alleging that the IRS had wrongfully levied upon its property. The district court granted the government’s motion to dismiss, concluding that Supermail had not filed suit within the limitations period set forth in 26 U.S.C. § 6532(c).
DISCUSSION
The sole question on appeal is whether the district court was correct in holding that this action is time-barred. Viewing the complaint’s allegations in the manner that we are required to view them, we conclude that Su-permail could prove a set of facts that would establish that equitable tolling applies and that the action was timely. We therefore hold that dismissal was improper.2
Because the applicability of the equitable tolling doctrine often depends on matters outside the pleadings, it “is not generally amenable to resolution on a Rule 12(b)(6) motion.” Cervantes v. City of San Diego, 5 F.3d 1273, 1276 (9th Cir.1993). A motion to dismiss based on the running of the statute of limitations period may be granted only “if the assertions of the complaint, read with the required liberality, would not permit the plaintiff to prove that the statute was tolled.” Jablon v. Dean Witter & Co., 614 F.2d 677,
1
Although the letter from the IRS purports to deny the "claim, dated April 8, 1993," it does not appear that any claim was filed on that date.
2
The district court erroneously believed the statute of limitations contained in 26 U.S.C. § 6532(c)(1) to be a jurisdictional prerequisite and, accordingly, dismissed under Rule 12(b)(1) for lack of subject matter jurisdiction. In doing so, the district court overlooked the Supreme Court's decision in Irwin v. Department of Veterans Affairs, 498 U.S. 89, 96, 111 S.Ct. 453, 457, 112 L.Ed.2d 435 (1990) and this court's decisions interpreting Irwin. As we stated in Washington v. Garrett, 10 F.3d 1421, 1437 (9th Cir.1993), the Irwin Court "held that federal statutory time limitations on suits against the government are not jurisdictional in nature.” Because the question whether Supermail's claim is barred by the statute of limitations is not a jurisdictional question, it should have been raised through a Rule 12(b)(6) motion to dismiss for failure to state a claim, not a Rule 12(b)(1) motion to dismiss for lack of jurisdiction. We therefore treat the dismissal as one under Rule 12(b)(6).