If the executor makes written application to the Secretary for determination of the amount of the tax and discharge from personal liability therefor, the Secretary (as soon as possible, and in any event within 9 months after the making of such application, or, if the application is made before the return is filed, then within 9 months after the return is filed, but not after the expiration of the period prescribed for the assessment of the tax in section
6501) shall notify the executor of the amount of the tax. The executor, on payment of the amount of which he is notified (other than any amount the time for payment of which is extended under sections
6161,
6163, or
6166), and on furnishing any bond which may be required for any amount for which the time for payment is extended, shall be discharged from personal liability for any deficiency in tax thereafter found to be due and shall be entitled to a receipt or writing showing such discharge.