If your wife does not have a driver's license or state ID, she can leave that line blank.
In our ongoing effort to protect taxpayers from identity theft, the IRS, state tax agencies and the tax industry do ask for the taxpayers’ driver’s license number or a state-issued identification number. This information is optional for most state tax returns, but a few states do require it to complete the electronic filing process. It is also optional for a federal tax return. However, providing these identification numbers helps the IRS verify your identity which can prevent unnecessary delays in tax return processing. You also can review state revenue department websites for information.
You do not need a driver’s license number to file your federal tax return. But, in an effort to better protect you from identity thieves, some states will be trying new approaches. Some states may ask for additional identification information, such as your driver’s license number, when you are preparing your state tax return. This will be another layer of protection because identity thieves may already have your name and Social Security number, but perhaps not your driver’s license number. States requesting this information have the ability to match driver’s license information and other identifying records to help confirm your identity.
