How do I sign my return? The most convenient way for you to sign your electronic return is to use an electronic signature Personal Identification Number (PIN) -- and it's completely paperless. Your tax preparer can answer any questions you have about electronic signatures. In addition, the IRS will accept a scanned Form 8453-EO signature document, which must be in PDF format. This option is available to filers who elect not to use a PIN to sign the return or who use an On-Line Provider to file. Filers who are filing for themselves and not using a third party provider must use Form 8453-EOPDF to sign the return. The PIN option is available to those who use a third party provider.