Memo from the Internal Revenue Service to retirement investors: Be careful with those individual retirement account rollovers.

That's the gist of a recent IRS ruling that puts new restrictions on the number of "indirect rollovers" from one IRA to another you can do annually. The ruling comes on the heels of a federal court decision in January in which a complex strategy involving multiple rollovers executed by a New York City tax attorney, Alvan Bobrow, and his wife, Elisa, was disallowed. They were hit with a $51,298 income tax bill and a penalty of $10,260.

The new IRS rule only affects indirect rollovers, in which money isn't sent direct from one financial trustee to another. Until now, such rollovers were permitted once every 12 months from each IRA account that a taxpayer owns. Starting January 1, 2015, the 12-month rule applies to all IRAs a taxpayer owns collectively. (Rollovers completed in 2014 won't be affected.)

An indirect rollover allows an investor to withdraw funds from an IRA and then take up to 60 days to reinvest the proceeds in a different IRA without incurring income tax liability or the 10 percent withdrawal penalty for investors younger than 59 1/2. The court case, Bobrow v. Commissioner, involved several large indirect rollovers (just over $65,000 apiece) in 2008.

At issue is a sophisticated strategy, allowable under the old rules, aimed at drawing what amounts to an interest-free loan through a series of indirect rollovers. It's usually executed by financial advisors or other financial experts because the penalties for mistakes are severe.

"We've executed it with a handful of clients over the past decade," says Michael Kitces, partner at Maryland-based Pinnacle Advisory Group, "although I usually caution strongly against it, because if you botch it for any reason, you can't fix it."

In this case, Bobrow took an indirect distribution of $65,064 from his IRA in April 2008. In June he took a distribution of the same amount from a second IRA and four days later used those funds to repay the first IRA. In July he took a third distribution of that amount from an IRA owned by his wife, repaying that money into his second IRA days later. In September he made a final deposit to repay his wife's IRA.

The IRS held that the timing of some of the transactions didn't comply with the 60-day rule, and other aspects of the maneuver violated its rules. Bobrow sued the IRS, but the court wound up not only backing the IRS on the issue of the Bobrows' timing but also ruling more broadly that all indirect rollovers are subject to an aggregate once-per-year rule.

That set the stage for the IRS rule that takes effect next year, which aims to clamp down on this maneuver. It applies to transfers from one IRA to another, or from a Roth IRA to another Roth account. It also covers SEP (simplified employee pension) plans and Simple (savings incentive match plan for employees) IRAs. It doesn't apply to rollovers from a workplace account to an IRA, or to Roth conversions.

The rule has caused a stir among financial advisors because it contradicts language in IRS Publication 590, which spells out the IRA rules. (The IRS will amend the publication.) Nonetheless, the shift should not pose problems for most taxpayers, who typically execute rollovers directly between financial institutions.

"People really shouldn't do indirect rollovers," says Ed Slott, an IRA educator and author. "The only advantage is to get temporary use of the money, and that's not really the spirit of the law."

Slott says some financial institutions do make it tough to execute direct rollovers, which could lead some taxpayers to the indirect route.

"I've heard of cases where the investor goes into a bank or brokerage and the staff person doesn't know how to do a trustee-to-trustee transfer -- or they try to talk the customer out of moving the money to another institution," he says. "So, the investor will say, 'Just give me a check, I haven't decided what to do with it yet.' "

Slott thinks the safest way to handle rollovers is direct trustee-to-trustee -- with the receiving institution doing the paperwork. "If you are moving from bank A to broker B, broker B is getting the money, so let him do the paperwork. He'll do it the right way, because he has an incentive to do so."

But I'll wave a caution flag: Don't use an advisor simply because she offers to streamline your paperwork. Brokers and other financial advisors may be able to help you do the rollover paperwork, but you still need to do due diligence on the quality of investments offered and the fees charged. The U.S. Labor Department is gearing up to propose broad new rules later this year that would require brokers to act as fiduciaries, including when they advise clients on rollovers.