Do you mean how to pay your tax due to the IRS or your state? You make out a check payable to the U.S. Treasury for federal and mail it with the 1040V voucher. Use a mailing service that will track it like UPS or certified mail so you know it was received. https://www.irs.gov/filing/where-to-file-paper-tax-returns-with-or-without-a-payment
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