These are the 3 biggest retirement plan rollover mistakes, expert says. Here’s how to avoid penalties

“The biggest one is breaking the one-per-year IRA to IRA rollover rule,” Appleby told CNBC. “And that happens because people are impatient.”

Generally, you can’t make more than one IRA rollover from the same IRA within a 12-month period, she explained. Otherwise, you must include the rollover in gross income and it may be subject to a 10% early withdrawal penalty before age 59½.

Plus, the IRS treats the additional rollover as an excess contribution, which triggers a 6% levy per year for every year the money stays in the new IRA.

Another common mistake is missing the 60-day retirement plan rollover deadline, Appleby said.

You have 60 days to complete a retirement plan or IRA rollover and the clock starts ticking when you receive the proceeds, she explained.

“People have good intentions and then life happens,” she said. Generally, missing the 60-day deadline means treating the money as a taxable distribution — unless you qualify for an IRS waiver.

Most retirement plan distributions are taxable and trigger a 10% early withdrawal penalty unless you qualify for one of the exceptions.

However, these exceptions are account-specific and may not apply after transferring money from a 401(k) to IRA, or vice versa. “That happens quite a lot,” Appleby said.

For example, there’s a 10% penalty exception of up to $10,000 for first-time homebuyers for IRAs, but not 401(k) plans. And there’s no exception for leaving your job at age 55 or older, known as “separation from service,” when pulling the money from an IRA. That’s typically in play for employer plans such as 401(k)s.

That’s why you need to check the list before rolling over funds to see if you lose eligibility for certain exceptions, she said.