I also disagree with @Opus 17 ...I don't think you are considered covered by a defined contribution plan if you opt out
https://www.irs.gov/retirement-plans/common-errors-on-form-w2-codes-for-retirement-plans#:~:text=For...).
Form W-2, Box 13
The “Retirement plan” indicator in Box 13 shows whether an employee is an active participant in your company’s plan. If this box is checked, it lets the recipient know that depending on their filing status and modified adjusted gross income, they may not be entitled to a full deduction for their traditional IRA contributions. You should check the retirement plan box if an employee was an “active participant” for any part of the year
Active participant
Generally, an employee is an active participant if covered by a:
- defined contribution plan (for example, a 401(k) plan) for any tax year and is credited with any contributions or forfeitures, or
- defined benefit plan for any tax year that the employee is eligible to participate.
