Even if he amended his tax filing to correct it...his amended tax return can take several months to get manually processed after he mailed in his amended tax forms (and he does have to mail them in himself).
And even then it can take awhile for the IRS computer systems to sync-up to allow you to e-file.
So your choices are to either:
1) Switch to file-by-mail and mail yours in too.
or
2) File the extension forms that allow you to efile up to ~ 15 October. If you have an expected balance due, you pay that wiht yoru extension forms now. Then, after those are submitted, you can continue to try to efile...say, once a month until October...but if it doesn't go thru by mid-Sept....then You'd give up and switch to file by mail anyhow.
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If you do end up filing by mail. Federal and state forms are mailed (by YOU) separately to different addresses....sign/date, attach appropriate copies of any W-2 forms to each, plus any other tax forms that show Federal (or state) withholding. And when you mail them off, go to the Post Office, use a tracking method, like Certified Mail, ath teh Post Office Service counter.
IF you decide to file an extension..there are a bunch of instructions and faq links here (but I've never done it myself):
<a rel="nofollow" target="_blank" href="https://ttlc.intuit.com/questions/1900551-can-irs-extensions-be-e-filed">https://ttlc.intuit.com/questions/1900551-can-irs-extensions-be-e-filed</a>