If you are referring to the document ID number, this number is an 8 or 10 digit alphanumeric number found either on the back of the license or lower right hand corner (depending on the year of your license). It is not the same as the drivers license number. I have included a link to the NY authority that displays images below. This link will also show you where the regular state ID number is (but its the document number that usually causes problems for people to find)
**Some licenses depending on issue date don't have these document numbers on them. Review the link above, but if you do not have a document number, then you can continue without actually entering any of the license information (leave it all blank, not just the document number). Your return will still be processed without it as the IRS does not require the license number and neither does NY, but they are asking for it more of an identity protection measure (some states like Alabama and Illinois are requiring it).
