I am a UK citizen. I married a US citizen in March 2009 and am planning to move to Florida but am not yet a Green Card holder. I want to transfer about US$200,000 to pay off my husband's mortgage and build a second house on his plot. Will my husband or I have to pay tax for the money transferred ?

No, there is no tax to be paid in the U.S.
If it is a gift to your husband, then he may need to file Form 3520.

The form is due of the date of your return including extensions.The form is filed at Internal Revenue Service, P.O. Box 409101, Ogden, UT 84409
Your U.S. Tax Return: The U.S. Gift Tax (http://taxipay.blogspot.com/2008/03/us-gift-tax.html)

There is no such thing as a gift to a spouse as, in US tax doctrine, a married couple is a single economic entity.

Nevertheless, estate tax laws in the US differentiate between a citizen and a green card holder and I would strongly advise you to seek out professional council in Florida to compose your wills in such a way as to minimize or eliminate any tax consequences from estate tax obligations.

There is no such thing as a gift to a spouse as, in US tax doctrine, a married couple is a single economic entity.

Yes, Five Rings may be right.
There is a limit to the amount of nontaxable gift a U.S. person can give to nonresident spouse
"For calendar year 2008, the first $128,000 of gifts to a spouse who is not a citizen of the United States (other than gifts of future interests in property) are not included in the total amount of taxable gifts under §§ 2503 and 2523(i)(2) made during that year."

So I assumed that there must be some IRS reporting requirements if nonresident spouse sends a gift exceeding a certain amount. I may be wrong.

MukatA:

While your citation is correct, look at WHO is giving the gift. In this case, the U.K. citizen is gifting the money to the U.S. citizen, so the amounts cited by you do not apply.