31 C.F.R. § 800.1108
The Staff Chairperson may reject a voluntary notice under § 800.504(a)(3) upon a determination that the amount of the filing fee paid by the parties was insufficient under this subpart. Prior to rejecting a notice under § 800.504(a)(3) , the Staff Chairperson shall inform the parties in writing of the insufficiency of payment and provide the parties three business days to pay the remainder of the filing fee. If the Staff Chairperson does not reject a voluntary notice under § 800.504(a)(3) upon a determination that the amount of the filing fee payment paid by the parties was insufficient under this section, the balance of the fee remains payable unless the Staff Chairperson notifies the parties in writing that the payment has been waived in whole or in part.
31 C.F.R. §800.1108