Take a tip from Serena Williams: You can’t just deposit a $1 million check at your bank’s drive-through.

The tennis great learned that lesson when she indeed tried to make such a hefty deposit early in her career. In a recent interview on the popular “Hot Ones” talk show on YouTube GOOGL GOOG — yes, the program where guests eat progressively spicier hot wings as they talk about life and career — Williams recalled that she was so focused on her play that she never thought much about her tournament winnings, be it collecting them or eventually putting them in a bank account.

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So, when it came time to make that big deposit, she assumed the quick-and-easy option would be acceptable, only to learn otherwise from a bank employee.

“I went through the drive-through,” she said. “The guy was like, ‘Uh, I think you need to come inside for this.’ ”

And that’s pretty much what can happen to anyone, financial professionals told MarketWatch.

Banks are always careful when customers present them with a sizable check (or a sizable sum of cash), especially if it’s much larger than the customer’s typical deposit amount. That’s because banks are concerned about possible instances of money laundering or anything else that’s suspect, said Kevin Manning, lead wealth adviser with Regent Peak Wealth Advisors, an Atlanta-based firm.

“They certainly do want your money, but, at the same, they have a responsibility to monitor for any fraudulent behavior,” Manning said.

In fact, banks are required to file reports with the federal government for cash transactions greater than $10,000 or for any “suspicious activity that might signal criminal activity,” according to what’s called the Bank Secrecy Act.

Manning said policies on how to handle large deposits vary from one financial institution to another, but it’s best to contact your bank before you show up with that $1 million check in order to know what might be asked, or required, of you. At the very least, be prepared to explain the source the large deposit, Manning added.

You should also be aware that a $1 million deposit is not fully insured by the Federal Deposit Insurance Corp., financial professionals note. The FDIC places a $250,000 limit per depositor on accounts at any FDIC-insured bank.

If that concerns you, Mark Gianquitti, a director with O’Connor Capital Partners, a development and investment firm, said your best option may be to spread that $1 million among four banks, maxing out the $250,000 amount per institution.

Gianquitti noted that the likelihood of any bank going insolvent is remote, “but I’d breathe a little easier knowing that the full million is guaranteed.”

Of course, if you’re parking $250,000 or $1 million — or frankly any sizable amount — at a bank for any period of time, it’s important to make sure you’re getting the best interest rate possible, financial experts add. These days, savings accounts that offer at least a 5% rate are widely available.

People making large deposits would also benefit from talking with a financial institution’s private-banking department, according to professionals. Such departments can not only discuss savings rates in detail, but also may be able to provide key benefits, such as a reduction on credit-card or mortgage interest rates.

In other words, don’t just make the deposit, but also look to build a relationship. “Speaking to somebody,” Manning said, ”is extremely important.”

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