If you shop online — and who doesn’t? — you might notice that some websites let you pay with bitcoins.Virtual or crypto currencies like Bitcoin can be a fast way to pay online, or in person with a mobile app.

But using virtual currencies comes with risk. Their value goes up and down — sometimes sharply — depending on demand. In addition, payments made with virtual currencies aren’t reversible and don’t have the same legal protections as some traditional payment methods. Once you hit send, you can’t get your money back unless the seller agrees. That’s why it’s important to know who you’re buying from and what policies they have regarding refunds, returns, and disputes.

In fact, the FTC has received hundreds of complaints involving bitcoins and other virtual currencies. The two most common problems? Online merchants who don’t deliver the product on time — or at all — and merchants who give refunds in store credit, rather than currency.

If you decide to use bitcoins or other virtual currencies as payment, here are some tips:

Know where you’re sending your bitcoins.

• Check out the seller’s reputation. Make sure you know where the seller is located and how to contact someone if there are problems.
• Find out whether the payment will go directly to the seller, or through a payment processor, which may offer you additional protections.
• If you pay with bitcoins, the only way to get a refund is through the seller or payment processor, so it’s important to choose companies you trust.

Understand the refund and return policies.

• If you receive something that’s damaged, how will the seller make it right? Will you get a refund in virtual currency, US dollars, or store credit?
• How much will your refund be? The value of a bitcoin changes constantly so the seller should tell you before you buy what exchange rate will be used for refunds.
• How will your refund be processed? To refund a credit card purchase, the merchant usually credits the account. However, because people can change their virtual wallet accounts, a seller can’t always send a bitcoin back to the wallet it came from.

Find out how your information is protected.

Bitcoin and other virtual currencies post transactions on a public ledger, which typically includes the amount and the wallet addresses of the sender and the recipient. Read the seller’s privacy policy to find out what other information might be collected and shared. If the seller uses a payment processor, check its privacy policy, too. A recent FTC report found that many shopping apps had privacy policies that included broad rights to collect, use, and share data.

If you have a problem with a bitcoin-related product or service, file a complaint with the FTC.