Envelopes that cannot be re-metered or used shall be voided by writing "Void" across the stamp. They shall be stored in a secure place and taken to the post office the next time additional postage is purchased and the meter is reset or sooner if quantity presents storage problems. Post Office Form 3533 shall be completed in duplicate and presented to obtain the meter adjustment in an amount totaling 90 percent of the value of the voided postage. Due to the extra procedures, cost of envelopes involved and a 10 percent loss in refund for the voided postage, proper care in the use of the postage meter must be exercised to minimize the voiding of metered envelopes.