Dear Readers: Believe it or not, and despite great efforts to deter it, counterfeit money is still out there. And the surprising places it’s showing up? The family garage, yard or tag sale, and at meetups arranged through online purchases.

At a garage sale, the person with the bad bill will wait until the seller is very busy. Then he or she will ask the seller to make change. Be sure to study the bill given to you closely. Look for the security features built into it: the color-shifting ink on the bottom right corner, and the watermark. For online sales, meet the purchaser either at a police substation or at a bank — anywhere that has lots of cameras, and where you can verify the authenticity of the bill.

— Heloise