I am a green card holder and I just got married to a US citizen. We got married out of the US. Do we have to submit any particular documentation since we are planning to file taxes together? My company filed for my green card a long time ago.
The only document you need to submit to indicate that you're filing a joint tax return is the tax return itself. If you were married in 2019, the first tax return for which you'll do this is your 2019 tax return, due in April 2020. If you were married earlier this month then you'll have to wait a year; your filing status for your 2019 returns will remain single or whatever it was before you were married.
If either the permanent resident or the citizen is changing his/her name as a result of the marriage, that partner will need to obtain a new social security card, as well as all the other steps in changing one's name. If either or both partners are employed, the employee may wish to file a new form W-4 with their employer so taxes withheld will be more accurate.