If you arrive home from the store and discover that one of the articles you purchased still has the magnetic security tag attached, you may be able to remove it yourself, which will save you a trip back to the store.
Call the store, and ask if their security tags contain ink. Some security tags spray ink if you try to remove them, which can ruin your purchase. Explain why you're asking so they won't think your intent is to shoplift.
Place the item in the freezer for two hours to solidify the ink if the store uses tags that contain it.
Buy two neodymium magnets from a local computer store. You can also harvest magnets from an old computer hard drive. Don't use ordinary magnets since they won't be strong enough.
Remove the item from the freezer, and lay it on a firm surface with the dome-shaped knob on the magnetic tag facing up.
Stack the two magnets on top of one another, and hold them against the dome on the surface of the security tag. Use your hand to pull the pin underneath out, and remove the tag from your purchase.
Keep the receipt for all purchases. With the receipt, you can take the item back to the store, and ask them to remove it.
Remove magnetic security tags only from items you've purchased.