It's the deduction for a traditional IRA contribution that might be limited by MAGI, not the contribution itself.
If you are not an active participant in an employer plan you will not be subject to the limitation. With respect to the 401(k), active participation means that additions are made to your 401(k) either by you or by your employer for the plan year ending with or within the tax year for which the IRA contribution is being made. Additions can be employer contributions such as matching contributions or from forfeitures by employees who leave the company before becoming fully vested in employer contributions. You will also be an active participant if your employer provides you with a pension plan in addition to the 401(k), but these are becoming less common. It can also be complicated to determine which years you actively participated if the plan uses a fiscal year instead of a calendar year Your employer will indicate to you and the IRS that you are an active participant for a particular calendar year by marking box 13 Retirement plan on your W-2 for that year.
