You are not required to file if your Virginia Adjusted Gross Income is beneath the threshold. This is not the same as your income earned in Virginia.
It is your federal income adjusted to Virginia's tax law. It is usually not much different than the AGI reported on your Federal 1040 Line 11.
If you earned $80,000 federally, even if only $2,000 of that was in Virginia, you are required to file a Virginia nonresident return.
Like every state, Virginia only taxes the income sourced by their state for a nonresident return, but the calculation to determine if you must file is based on your federal AGI.
For more information on nonresident returns in Virginia, see the 763 Instructions. See page 10 of the pdf for information about nonresident filing requirements.
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