You must have an underpayment Penalty. Answer the questions don't worry about it. The tax liability is not if you had a tax due. It is the tax on your total AGI before you got a refund or tax due.
Here's some general info on getting married. Did you both use Turbo Tax last year?
You can not transfer from or combine 2 returns or accounts. Just pick the return for the spouse that has the most complicated return to enter or has any depreciation or business or more investments. Or use the account for whoever you want to be listed first going forward (by the way you can not change the order of the names). Then add the other spouse's name, ssn and info to it.
You should usually file a Joint return which is only 1 return combined for the both of you. Make sure to stick with this one account for the future. Just ignore the other spouse's account.
And info on Getting Married…..
Is it better to file Joint or Separately?
Compare Joint to Married Filing Separately
Do you mean 2018 AGI? That is what the IRS used to verify your identity when e-filing.
If you did not file a 2018 tax return at all then it is 0.See this TurboTax FAQ on how to find your AGI
You can get free 2018 tax transcript from the IRS
If you filed late last year there is a good chance that the 2018 AGI never was entered into the e-file database. Try using 0 (zero) for the AGI.
If you filed an amended return use the AGI on the first filed tax return.
If it continues to reject then the AGI in the IRS database might be in error. Mail filing is the only option.
It is asking for your 2018 AGI --that is how the IRS matches you up with the person who used your SSN last year so that you can e-file 2019. Look at each of your 2018 tax returns on line 7 for your 2018 AGI.
You can get a free transcript from the IRS:
If you have federal tax due you can pay by mailing your payment with the 1040V voucher, having the payment taken out of a designated bank account, or you can pay directly on the IRS website.
You must pay your state tax due using the state’s preferred method of receiving payment. For most states that will be by making a payment to the state’s own tax website, or by mailing a check or money order.