In certain cases, the taxpayer's payments in respect of his tax liability, made before the filing of his return, may exceed the amount of tax shown on the return. For example, such payments may arise in the case of the income tax when the estimated tax or the credit for income tax withheld at the source on wages exceeds the amount of tax shown on the return, or where a corporation obtains an extension of time for filing its return and makes installment payments based on its estimate of its tax liability which exceed the tax liability shown on the return subsequently filed. In any case in which the district director or the director of the regional service center determines that the payments by the taxpayer (made within the period prescribed for payment and before the filing of the return) are in excess of the amount of tax shown on the return, he may make credit or refund of such overpayment without awaiting examination of the completed return and without awaiting filing of a claim for refund. However, the provisions of Sec. Sec. 301.6402-2 and 301.6402-3 are applicable to such overpayment, and taxpayers should submit claims for refund (if the income tax return is not itself a claim for refund, as provided in Sec. 301.6402-3) to protect themselves in the event the district director or the director of the regional service center fails to make such determination and credit or refund. The provisions of section 6405 (relating to reports of refunds of more than $100,000 to the Joint Committee on Internal Revenue Taxation) are not applicable to the overpayments described in this section caused by timely payments of tax which exceed the amount of tax shown on a timely return.