This is from the IRS web site:
You’re covered by an employer retirement plan for a tax year if your employer (or your spouse’s employer) has a:
Defined contribution plan (profit-sharing, 401(k), stock bonus and money purchase pension plan) and any contributions or forfeitures were allocated to your account for the plan year ending with or within the tax year;
IRA-based plan (SEP, SARSEP or SIMPLE IRA plan) and you had an amount contributed to your IRA for the plan year that ends with or within the tax year; or
Defined benefit plan (pension plan that pays a retirement benefit spelled out in the plan) and you are eligible to participate for the plan year ending with or within the tax year.
Box 13 on the Form W-2 you receive from your employer should contain a check in the “Retirement plan” box if you are covered. If you are still not certain, check with your (or your spouse’s) employer.
