Dear Liz: I am 41 and have had a traditional IRA for about two decades. I funded it for the first 10 years, taking a tax deduction for the contributions. Since I’ve had a 401(k) with my employer for the past several years, I obviously cannot take a deduction for the IRA amount, but I could still put money in. My 401(k) is fully funded, as is my husband’s. Does it make sense to also fund our IRAs with post-tax, nondeductible amounts? I realize any gains we make will be taxed at withdrawal, but I also know that as long as the money stays in the IRA, it can grow tax deferred.

Answer: First, congratulations on taking full advantage of your workplace retirement plans and still being able to contribute more.

You potentially can deduct contributions to IRAs when you have a 401(k) or other workplace retirement plan, but your income must be below certain limits. You can take a full deduction if your modified adjusted gross income is $104,000 or less as a married couple filing jointly. After that, the ability to deduct the contribution starts to phase out and is eliminated entirely if your modified adjusted gross income is $124,000 or more. (If you don’t have a workplace retirement plan but your spouse does, the income limits are higher. The deduction starts to phase out at $196,000 and ends at $206,000.)

If you can’t deduct contributions, you can look into contributing to a Roth IRA — but that too has income limits. For a married couple filing jointly, the ability to contribute to a Roth begins to phase out at modified adjusted gross income of $196,000 and ends at $206,000. If you can contribute, it’s a good deal. Roth IRAs don’t offer an upfront tax break but withdrawals in retirement can be tax free. You also can leave the money alone for as long as you want — there are no required minimum withdrawals starting at age 72, as there typically are for other retirement accounts.

If your income is too high to contribute to a Roth, you could still contribute to your IRA or to any “after tax” options in your 401(k). But you might want to consider simply investing through a regular taxable brokerage account. You don’t get an upfront tax deduction but you could still benefit from favorable capital gains tax rates if you hold investments for a year or more. Furthermore, you aren’t required to take withdrawals. That flexibility can help you better manage your tax bill in retirement.