I am married and in the process of filing jointly.
For the moment, lets talk about you, and you only. Since your wife has no 2019 income from anywhere on the planet to report, this does simply stuff - but that doesn't mean it's easy. 🙂
I lived in MA till August of 2019,....I was a student in MA
Was your primary purpose for being in MA, to attend school? If yes, then that does not make you a resident of MA. But other factors such as voter registration, getting an MA drivers license, MA car registration and other things, very well could make you a resident. So first, determine your MA residency status.
Assuming your primary reason for being in MA was to attend school, you should read TIR 95-7 and make "sure" you read all the examples - every one of them. Even if your primary purpose for being in MA, there are conditions where you would still be considered a resident of MA and taxed as such. As a resident of MA, "all" of your worldwide income is subject to MA state taxes.
after which I moved to MO in September.
More than likely, MO may consider you a part year resident. But MO makes the determination rather easy with a simple flow chart at https://dor.mo.gov/pdf/nonres_flowchart.pdf
As for the wife:
she moved to NY for grad school.
Relocating for the primary purpose of attending school does not change her state of residency. No need to worry about NY taxes, or any other state besides MA and MO since she has no reportable income for 2019.
Therefore, on your joint tax return indicating that she was a resident of the same state you claim residency in, or that she was a resident of another state, will have no impact on your tax liability, or filing requirements.
