How do I know my 2018 extension has gone to the IRS?

[KevinH · Accepted solution]

If you filed your extension electronically using TurboTax, you'll receive emails updating you on the acceptance status with the IRS.  

[RPM000]

What if you did not file electronically through TurboTax? How do you receive status it was received?

[DoninGA]

Get a transcript of the Tax Account it will have the payment made with the extension request - https://www.irs.gov/individuals/get-transcript

Since the date has passed for filing a tax return with an extension then whether or not your extension was accepted is a moot point.