First, your return can be filed and will process
without your drivers license number.
You do not need a driver’s license number to file a
federal return.
Some
states may request your driver’s license number for state tax returns because
they have the ability to match state records and help confirm your identity.
This is one more layer of protection against identity thieves.
You can review state revenue department
websites for information.
Also,
you may find the following information helpful:
State
Driver's License Input