Dear Liz: I turned 70 last week and therefore I am leaving my part-time job after about 13 years. No big deal, but now that I am retiring I have a 401(k) worth about $60,000 and an IRA that is somewhere around $50,000. Should I roll my 401(k) account into my IRA or just let it sit there collecting dust? I do understand that at age 70½ I am supposed to start withdrawing some of the funds, but am not sure how much. It seems 70 years creeped up on me.

Answer: Years have a nasty habit of doing that.

You mentioned that you’re retiring because you’ve achieved a certain age. Few jobs have mandatory retirement ages, though. If you don’t retire, you can continue putting off required minimum distributions from your 401(k). You would still have to take minimum distributions from your IRA, unless your employer allows you to roll that money into your 401(k) plan.

But we’ll assume you’re happy with your decision. Rolling your 401(k) into your IRA isn’t necessarily the best option. What you should do next depends on the details of both accounts.

Most large-company 401(k)s allow retirees to take regular distributions, including required minimum distributions, from the plans. These plans also tend to offer low-cost institutional funds that may be a much better deal than those you can access as a retail investor with an IRA. If you’ve got a good 401(k) that allows retirement distributions, there may be no need to move your money.

If your employer’s plan doesn’t allow such distributions, don’t automatically assume your current IRA provider is the best choice, especially if it’s a full-service brokerage or insurance company. Compare the fees of the investment options with what’s available from a discount brokerage. Transferring all your retirement money to a lower-cost provider can help you keep more money in your pocket.

Calculating your required minimum distributions isn’t difficult. The IRS has tables on its website, and in Publication 590, to help you figure out how much money to withdraw. Various sites have calculators as well.

One caveat: If you keep your IRA and 401(k) separate, you’ll have to calculate required minimum distribution separately for each account and withdraw those amounts from each account, says Mark Luscombe, principal analyst for taxes and accounting at Wolters Kluwer. That’s different from the rules when you have multiple IRAs. When you have more than one IRA, you calculate the required minimum distribution based on the total of all your IRAs but are allowed to take the distribution itself from any one of them.