When any person fails to make any return or pay the full amount of tax required by § 58.1-1402 within thirty days of the required filing and payment date, there shall be imposed, in addition to other penalties provided herein, a penalty to be added to the tax in the amount of six percent of the unpaid tax. An additional six percent of the tax due shall be charged for each additional thirty-day period, or fraction thereof, after sixty days, during which the failure to make any return or pay the full amount of tax continues. Such additional penalty shall not exceed thirty percent in the aggregate. If any such failure is due to providential or other good cause, shown to the satisfaction of the Commissioner, the return, with remittance, shall be accepted exclusive of such penalties, but with interest determined in accordance with § 58.1-15. In the case of a false or fraudulent return, where willful intent exists to defraud the Commonwealth of any tax due under this chapter, or in the case of willful failure to file a return with the intent to defraud the Commonwealth of any such tax, a penalty of fifty percent of the amount of the proper tax shall be assessed. It shall be prima facie evidence of intent to defraud the Commonwealth of any tax due under this chapter when any purchaser or user of a watercraft reports the sale price or current market value of his watercraft, as the case may be, at fifty percent or less of the actual amount. It shall also be prima facie evidence of intent to defraud the Commonwealth of any tax due under this chapter when any dealer reports the gross receipts collected from the lease, charter or other use of watercraft at fifty percent or less of the actual amount received for such lease, charter or use. All penalties and interest imposed by this chapter shall be payable by the purchaser or user of the watercraft and collectible by the Commissioner in the same manner as if they were a part of the tax imposed. Interest, at a rate determined in accordance with § 58.1-15, on the unpaid amount of the tax from the day after the last day for timely filing and payment of the tax shall accrue until the same is paid.