My mother has $150,000 she would like to gift to my sister. She has never used any of her gift exemptions and will not be gifting anymore than this in her lifetime. Can she gift this amount at one time and be exempt from any federal gift tax?

Yes, she will not pay any gift tax but she must file gift tax return. The taxable gift amount, which will be adjusted against life time exclusion, is $150,000 minus $13,000 (allowable amount). Your U.S. Tax Return: The U.S. Gift Tax (http://taxipay.blogspot.com/2008/03/us-gift-tax.html)