@JackRyan , assuming that you are a resident for tax purposes ( i.e. passed the Substantial Presence Test ) on your entry with H1-B visa, and you plan to file Married Filing Joint, your spouse's world income ( I am assuming that this is from a foreign country , per your post ) is subject to US taxes ( Federal and State ). If she has paid taxes on this income to a foreign tax administration, then that tax may be eligible for foreign tax credit ( however, you may not be able to get 100% benefit of this depending on the family's foreign income vs. world income ratio).
I am also assuming here that your spouse is living with you here on the USA.
Depending on the country of citizenship , and the exact facts and circumstances, treaty assertions may be possible.
As far as documentation to prove the income earned abroad etc. bank statements should be sufficient. You do not need to send anything to the IRS / State on this - just have it available in case of a challenge.
Is there more I can do for you ?
