Assuming this is your only job, If your work didn't begin offering the 401(k) until 2018, then you can say that you were not "covered" by an Employer Sponsored Retirement Plan on your 2017 Tax Return.
However, be sure to check ALL of your Form W2s to make sure there is not an "X" in the Retirement Plan Box 13. If any of your Form W2's have this Box checked, you are considered to be "covered" by an Employer Sponsored Retirement Plan the entire year.
