You don't even have to participate in a 401k plan; as long as an employer offers you a 401k plan, that "Retirement" box will be checked on your W-2 when the employer issues you a W-2 for 2014 in January 2015. With regard to deductability of Traditional IRA contributions, that will depend on your Modified Adjusted Gross Income (MAGI) for 2014, and your marital status as of December 31, 2014.

You don't even have to participate in a 401k plan; as long as an employer offers you a 401k plan, that "Retirement" box will be checked on your 2014 W-2 that your employer will send to you in January 2015. With regard to deductability of Traditional IRA contributions, that will depend on your Modified Adjusted Gross Income (MAGI) for 2014, your marital status as of December 31, 2014, and if you are married, then whether your spouse is covered by a retirement plan and your filing status (different thresholds for Married Filing Jointly and Married Filing Separately).