There are no tax implications if it is returned in the same year.
The person who makes the gift files the gift tax return, if necessary, and pays any tax. If someone gives you more than the annual gift tax exclusion amount ($15,000 in 2018), the giver must file a gift tax return. That still doesn't mean they owe gift tax.
The federal estate tax kicks in for estates that are worth more than $11.18 million, the same amount as the lifetime gift tax exemption. ... Gifts made each year in excess of the $15,000 annual limit per recipient reduce your federal estate tax exemption when you die.