Charge you didn't authorize

• Small recurring charges from names you don't recognize, often dating or 'membership' sites.
• A merchant charging again after a one-off purchase.
• Charges that begin soon after you entered your card on an unfamiliar site.
• 'Free trial' terms that turned into a monthly bill.

Small amounts slide past most people's attention, and by the time you notice, months have gone. Card details entered on one site can be sold or reused. Fine-print subscriptions are legal in some places and simply hidden in others. Either way, the charge continues until you stop it.

• Call the number on the back of your card, report the charge as unauthorized, and ask for a new card number if the details may have leaked.
• Check the last few months of statements for the same merchant.
• If you gave the card to a site a match or seller sent you, that's a known trick.
• Report it if it looks deliberate, and add the number here if a phone number was involved.

More in the tips: Buying, selling, and payment apps.