Dear Liz: I read your column answer to the 40-year-old who asked about regular 401(k) versus Roth 401(k) contributions. Obviously, the answer has more moving parts than you have space for. However, using before-tax dollars for the 401(k) gives him a small break now, but when he hits 70 1/2, those dollars will impact the taxability of his Social Security benefits. He could contribute to the 401(k) with after-tax dollars, get the company match and avoid that impact 30 years in the future, right?

Answer: The “right” answer requires knowing what tax rates will be 30 years in the future, at a time when no one is entirely sure what tax rates will be next year. Which means the smart approach is to hedge one’s bets. Given the original reader’s current financial situation, that translates into focusing most contributions into the pretax 401(k) but also making contributions to the Roth. That will give him some flexibility to control his tax bill in retirement without going “all in” on the bet that his tax rate then will be higher than it is now.