My employer does not offer a retirement plan. Their accountant erroneously checked the "Retirement Plan" box on my W-2 in Box 13, and when I brought it up to them they seemed not to care. I certainly don't expect them to issue a W-2C with no "X" in the Retirement Plan box. Furthermore there is no entry in box 12a showing an amount deferred, since there is no retirement plan offered.
A person who posed "what should I do" relative to this same question in 2019 got the response that they should enter the W-2 information as received, whether it is correct or not. Otherwise, they would get an audit letter.
This issue is important because it impacts the deductibility of a Traditional IRA. Is there really nothing that can be done if you have an employer that can't even be bothered with producing an accurate W-2?
Call the IRS toll free at 800-829-1040 or make an appointment to visit an IRS Taxpayer Assistance Center (TAC). The IRS will send your employer a letter requesting that they furnish you a corrected Form W-2 within ten days.
If your employer is not willing to correct the W-2, I suggest that you do not indicate that your employer has a retirement account, and that you do take the traditional IRA deduction that is within the limits.
If you do get a letter you can call toll-free at 1-800-829-1040 or visit a Taxpayer Assistance Center Local IRS Office