E-file rejected, now must pay by mail -- how do I pay federal taxes owed?

[et812]

I tried to e-file and was rejected due to a mismatched AGI. I want to choose the file by mail option now, but I owe federal taxes and TurboTax is saying I must choose another method to pay these taxes (not direct deposit, not credit card/debit card). I cannot mail a check. What do I do? I can pay online directly to IRS, but this is not an option when TurboTax asks: "How would you like to pay your federal taxes?" 

Do I select "Pay by check" but then pay online to IRS? If so, how do I make sure that the IRS knows that I paid the taxes? 

Thank you!

[Oldlady]

My son got a mismatch (where he just put 45 instead of 54 type of thing.  Anyhow, rejected, but he went into turbo tax last night and just put the right number in and refiled.  It didn't cost him anything and was quite easy.  Can you try to find the correct number from last years taxes and then just try again.  Even though it says, be sure its correct or else... it really was a no big deal thing to fix it and refile.  Within minutes the state sent a phone text stating that it was received received ok.

[et812]

Thanks, I tried twice and both times it said the AGI was wrong. I guess I could try one more time it might be because the IRS has a different number in their system, or haven't updated it yet on their end. They only just processed my return last month (submitted on time, it was just caught up in the delays). 

[Oldlady]

I had to do an amendment but in fine print it says don't use the amended amount, so I had to add to mine last years incorrect number that was the first into their system.  Then it took mine.  I still haven't gotten my return from my amendment.  My accountant added my 94 year old mothers social security to our income!!! :(  

[SForrestLO]

Please see this Turbo Tax FAQ on how to find your AGI from last year. 
https://ttlc.intuit.com/community/agi/help/how-do-i-find-last-year-s-agi/00/25947

How can I pay my federal taxes?
https://ttlc.intuit.com/community/tax-payments/help/how-can-i-pay-my-federal-taxes/01/26212

@et812