If my spouse was the only one who had a W-2 for 2018 taxes. Do I still use the 2018 AGI even if we’re “Married filing separately “?

[Anonymous]

if MFS in 2018 use your spouse's AGI only for your spouse. if you didn't file in 2018 use 0 for yours or if you did file use the amount from your  2018 1040 line 7

don't know why you chose MFS in 2018. it was not necessary if the only factor was that only one spouse had  income.  there is no requirement for both spouses to have income to file a joint return.  you can amend 2018 to switch to a joint return 

here are the steps if you decide to amend

https://ttlc.intuit.com/community/amending/help/how-do-i-amend-married-filing-separately-returns-to-...