Hi from Just Answer. Gift tax is one of those things that doesn't make sense, until you review the thinking behind it. to Q & A...
Gifts were one of the first ways people tried to get around US estate taxes, which are taxes on value. People would give gifts to the people who might inherit to avoid sometimes steep inheritance levies. Tax law has evolved to the point specific rules for gift taxes apply. When you give a gift over the exempt amount ($13,000), you use a part of your estate tax exception, known as the unified credit. If the donors have a taxable estate to be concerned about, gift taxes on current gifts, your question, come up.
The gift tax form, 709, allows the donors to split a gift between two spouses, so they can use one check. Two checks are not needed.
They can elect to pay the gift tax on the $9,000 or use some of their unified credit to make a tax free gift that reduces some of their unified credit. The gift tax, if one is to be paid, is due from the donor. Most elect to reduce their unified credit to avoid the 35% gift tax on value.
I hope this answers your question. Please advise if you need anything more. Thanks from Just Answer.