My husband sent his 1040 tax return from 2018 tax year. He sent all the applicable pages i.e. schedules that had 1040 under it as well. For him it was a total of 5 pages. He did not attach the other tax returns from 2016 and 2017. To fill out the i-864 form regarding previous income for 2017 and 2016 he just looked at the income made that year from his 1040. Did you not file your 2017 or did you lose it? I just wanted to let you know they do accept the 1040 forms because the NVC approved ours application. The same thing happened to my husband the IRS website wouldn't let him get his tax transcripts either. We are planning on bringing his 2016, 2017 tax returns as well as his 2018s and this years to show them at the consulate just in case they ask for it.