Question: I will be traveling to Vietnam. Am I legally permitted to bring Vietnamese currency into Vietnam from the United States? — Joe Joffino, Torrance, Calif.

Answer: You may take Vietnamese currency into Vietnam from the U.S. and vice versa.

Just for background: The dong is the national currency issued by the State Bank of Vietnam, the central bank. It is one of those currencies that makes doing math in your head a challenge. Last week 100,000 dong equaled about $4.40.

One of the easiest ways to learn about a foreign destination is the State Department website .

The rules are slightly different for taking money in or out of the U.S., said Evan Tarver said, a currency and investment analyst for FitSmallBusiness and a frequent traveler.

U.S. Customs and Border Protection doesn’t restrict the amount, but you do need to complete paperwork if it’s more than $10,000. Check out these pages to learn what forms you need and to reinforce that a family can’t split the $10,000 among themselves to avoid filing paperwork. (The money could be confiscated.)

If you’re visiting a developing nation, you may need a bit of cash, but otherwise, Tarver said, most transactions can be taken care of by credit card.

You can get foreign money at many U.S. banks, but author David Swanson said he took no Vietnamese currency on his Da Nang-Hue-Hoi An trip. Instead, he stopped at an ATM at the airport, where he withdrew between $50 and $100 to be used for cab fare and for small purchases in marketplaces or from street vendors.

Former Los Angeles Times travel writer Karin Esterhammer thinks that if you stick only with the places that take cards, you’ll miss the real essence of the country.

“You will need to pay with cash if you venture out beyond the center of the city, which, of course, you will want to do anyway,” she said in an email. “Small restaurants tucked into alleys and quaint old hotels will give travelers the real flavor of Vietnam. And carrying wads of 100,000-dong bills will make you feel rich!”

A word of warning: Check with your bank to see whether your Personal identification Number, or PIN, and debit card will work there or any country you’re visiting. Some countries like four-digit PINs and some, six. PINs are easy enough to change, but you would need to do this before leaving.

Finally, four tips:

>> If you get in a jam, U.S. dollars often are accepted, Swanson said. Most everything else can be bought with a credit card.

>> Call your credit card company to find out whether your card will be accepted at your destination and ask whether you need to notify the company about your upcoming trip.

>> Understand some credit cards incur foreign transaction fees. Jason Steele of the Points Guy website has a current roundup of cards that do not charge the fee .

>> Hide some cash, whether U.S., Vietnamese or both, and an extra credit card. If you lose it, or worse, you’ll have a backup.