You should fill in all spaces on immigration application PDF forms, if possible. If a question does not apply, you should leave it blank.
If you’re applying online and the form doesn’t let you leave the space blank, type “N/A” or “NA.”
For background/Schedule A questions
If you have to leave questions blank on Schedule A, you should include a letter of explanation that says why it doesn’t apply. This is so the officer doing your background check knows you didn’t forget to fill it in. Otherwise, that could delay your application.