What tax implications are there when you add a name to a deed?

Basically this is a gift from the original deed owner to the new person who is now a co-owner. The value of the gift would depend on how the property is titled, but if joint tenancy with rights of survivorship then basically the new person is a half owner, and the value of the gift is 1/2 the fair market value of the property as of the date of the gift. Gifts whose value exceeds the annual gift tax exclusion ($13000) must be reported using the gift tax form - form 709 - and an aparaisal will be required. No tax is due unless the value of this gift, plus any previous gifts that exceeded the annual exclusion in prior years, exceeds the lifetime exclusion of $1M. But even if no tax is due, there may be an impact on estate planning. Finally, when you sell the property, your tax basis is based on the original purchase price, plus your portion of capital improvements. More info here: Publication 950 (12/2009), Introduction to Estate and Gift Taxes