Any taxpayer filing electronically from a home computer must keep the signed Form PA-8453 and supporting documents for three years after the due date of the return or the date the return was filed electronically, whichever is later. Taxpayers must make the documents available to the PA Department of Revenue upon request. Do not mail Form PA-8453 and attachments to the PA Department of Revenue unless requested.
https://www.esmarttax.com/tax-forms/pennsylvania-form-pa-8453-instructions/
