The IRS allows you to correct most errors. However, there is one error you cannot fix that could seriously harm your retirement funds. It’s a relatively new rule (became effective Jan. 1, 2015), and if you aren’t aware of it, it can cost you dearly.

The rule: An individual can only do one 60-day IRA-to-IRA rollover per year (365-day period, not calendar year), regardless of how many IRAs he or she holds.

A 60-day rollover refers to when an individual cashes out an IRA and receives custody of the money; they then have 60 days to deposit the money in another IRA before taxes and penalties could be applied.

This rule does not apply to direct transfers from one IRA to another. A direct transfer — one in which the money is transferred directly from your IRA with one financial institution to your IRA with another institution — is the preferred method to move your IRA funds. You can do an unlimited number of direct IRA transfers.

The IRS considers a check made out to the receiving IRA as a direct transfer so it’s not subject to the one-per-year IRA rollover rule. However, a check made payable to you is considered an indirect rollover and is therefore subject to the rule.

Again, this rule applies no matter how many IRAs or Roth IRAs you own. As a general rule you should never, ever move your IRA or Roth IRA money as a 60-day rollover. However, the rule does not apply to rollovers from 401(k)s to IRAs, or from IRAs to 401(k)s or to Roth conversions.

Here’s an example of an eligible 60-day rollover: Sara withdraws $50,000 from her IRA on June 30, 2016. She returns it to another IRA on July 25, 2016 — well within the 60 days. Assuming she has not done any other IRA-to-IRA rollovers during the 365 days before June 30, 2016, then this is a good 60-day rollover. Caution: she cannot do another 60-day rollover from any of her IRA accounts until after June 30, 2017.

Here’s an example of an ineligible 60-day rollover: Omar wants to move his IRA, Roth IRA, and SEP IRA to his new adviser. Rather than complete the paperwork for a transfer, he asks his resigning broker to liquidate all three IRAs and send him the cash. He then makes new checks payable to the new broker for all three IRAs. Unfortunately, only one of those 60-day rollovers is good. The other two are ineligible.

So what happens if you violate the rules? Your IRA rollover will be an ineligible rollover and taxable to the extent of pre-tax funds withdrawn and may be subject to the 10% early distribution penalty (if you’re under age 59 ½ and no exception applies). Even worse, the ineligible rollover could be subject to a 6% excess IRA contribution penalty if the ineligible rollover is not removed in a timely manner.

But what if a direct transfer is just not possible? In some cases, 60-day rollovers are unavoidable. For example, some smaller banks and credit unions just won’t do direct rollovers. In this case, you need to monitor the one-year clock and keep track of all your IRA funds. Keep in mind that what you do in one IRA may affect all your other IRAs, and tread very carefully.