The federal tax depart' is requesting money for a flate tax report and money past due in 2017.i used turbotax system i 2017 and i was not late how can i proof it ?

If you send your return through NETFILE, you would need to find your confirmation number. This is proof that your return was filed successfully. https://turbotax.community.intuit.ca/questions/1518044-how-do-i-find-my-netfile-confirmation-number

If you sent your return via post, unless you sent it via registered mail, there is no way to be sure when/if the return was delivered to the CRA. If the CRA didn’t get it, then it may not have arrived.

You can also check My Account to see when the CRA got your return: https://turbotax.community.intuit.ca/replies/2647719