The IRS does not issue receipts or send confirmation to the taxpayer of an accepted extension request.
See this TurboTax support FAQ for printing the Form 4868 extension request - https://ttlc.intuit.com/questions/2879424-how-do-i-print-my-4868-extension-form-after-e-filing-it-th...
For an e-filed extension request use this TurboTax website to verify if the extension was accepted or rejected - https://turbotax.intuit.com/tax-tools/efile-status-lookup/
If accepted, print a copy of the extension status for proof of filing.
