If someone is an out-of-state (e.g., an NJ resident) filing an NY non-resident return, what does one use to fill in the 3-character document number?
As long as you are inputting a valid state ID from any state there should be no processing issues for NY.
For NJ driver's license, would the document# be the DL# or something else?
If your driver's license in New York was issued about 2012 or 2013 (like mine) you will need a magnifying glass, or zoom in all the way with your camera and take a pic of it because it looks like a red line in the lower right-hand corner, but is actually a tiny set of letters and numbers. I think some are on the front lower right corner or maybe on the back lower right corner.