I don't have my deceased spouse's 2018 AGI information to file my taxes for this year, what do I do?

So sorry for your loss.

 For the year that your spouse died, you can still file a joint return.  That way, you will get the married filing jointly standard deduction of $24,000 (+ $1300 for each spouse 65 or older) which will lower the amount of income you are taxed on.

In My Info, you will need to indicate that your spouse died. When her name is in My Info,  there is a screen early in the interview that asks "Do any of these apply to [name] ?’” where you will do that, and then a drop down will appear where you can enter the date she passed.

If you have dependent children still living at home, you will be able to file as a qualified widow for the next two years after this tax return.  Post back if you need further help.

As for the AGI---if you and your late wife filed a joint return for 2018---which would have been the  best way for you to file, the AGI is the same for each of you. It is on line 7 of your 2018 tax return.  But since your wife has passed away, you will not be able to e-file even with the AGI.  Your tax return needs to be printed, signed and mailed.

https://ttlc.intuit.com/community/printing/help/how-do-i-print-and-mail-my-return-in-turbotax-online/00/26258

When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s.  Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS/state received the return.

Federal and state go to different addresses.