You'll need to use
the AGI from your originally-filed 2017 joint return -- your combined amount on
the return.
Please see the
TurboTax FAQs below for a bit more information.
https://ttlc.intuit.com/replies/4231673
"What AGI should I enter if I'm
recently divorced or widowed?"
https://ttlc.intuit.com/replies/5534328
