19 CFR 141.91: Entry without required invoice.

If a required invoice is not available in proper form at the time the entry or entry summary documentation is filed and a waiver is not granted in accordance with § 141.92, the entry or entry summary documentation shall be accepted only under the following conditions:

(a) CBP is satisfied that the failure to produce the required invoice is due to a cause beyond the control of the importer;

(b) The importer files:

(1) A written declaration that he is unable to produce such invoice, and

(2) Any seller's or shipper's invoices available to him or, if none are available, a pro forma invoice in accordance with § 141.85;

(c) The invoices and other documents contain information adequate for the examination of merchandise, the determination of estimated duties, if any, and statistical purposes; and

(d) The importer files a bond on Customs Form 301, containing the bond conditions set forth in § 113.62 of this chapter, in an amount equal to one and one-half the invoice value of the merchandise, for the production of the required invoice, which must be produced within 120 days after the date of the filing of the entry summary (or the entry, if there is no entry summary) documentation, unless the invoice is needed for statistical purposes. If needed for statistical purposes, the invoice shall be produced within 50 days after the date of the entry summary (or the entry, if there is no entry summary) is required to be filed, unless a reasonable extension of time is granted by the Center director for good cause shown.