Jack is answering about the recipients basis where the recipient acquires the donor's basis (steps into the shoes of the donor).
If you are actually asking about how to prepare the gift tax return and about determining the fair market value at the date of the gift to report on Form 709, Sch A, column F, that is a much more complicated answer about how to determine the value of an ownership interest in a closely held business on a piece of property. If that is really what you are asking about -
If by property you mean real estate, I'd suggest your client use a qualified professional to appraise it because the documentation of how the FMV was determined is required to be attached to the gift tax return, and gift tax returns are reviewed by humans at the IRS. That is a risk area for tax preparers since doing valuations aren't within the normal scope of a tax preparation business. A typical scenario that I've encountered a few times goes something like this: A parent owns his own residence and a 2nd house that the child is living in (for little or no rent) and transfers that 2nd home to the child by gift. Yes, the child's basis comes from the donor's basis, but in preparing the gift tax return, the preparer must explain the method used and report the FMV on the date of the gift because that determines how much of the unified credit is used up by that gift and calculates whether there is a taxable component to the gift at all.
Business valuations are much more complicated and especially so when the business is closely held. There are business appraisers that do that too. There are methods that the IRS finds acceptable and that take into consideration a variety of factors that I feel are really beyond the scope of something that could be easily or completely explained here. Again, an explanation of the valuation method used must be filed with the gift tax return. If you are considering doing this, you might want to check with your malpractice insurance agent to make sure that type of service is covered.
As an example, I had a C corp client that gifted 76% of his ownership in his closely held business to his son in stages over several years. To highlight a few of the areas considered in that valuation, those factors included the type of industry, the size of the business by volume or asset base, its locale, its competition, stability of client base, discounts for lack of marketability due to being closely held, adjusting for owner compensation that might be in excess of what the business would pay an outsider or manager to perform those same duties, and much more. That list of factors isn't meant to be a full discussion, obviously, so don't shoot the messenger. I was only trying to show how business valuations are complex. A full explanation of how those valuations were done was attached to each and every gift tax return that was filed. No funds changed hands, the son received something that had appreciated close to 50 times more than the dad's basis in the company, and son's basis in the company is equal to 76% of dad's basis.
The gift tax return filed by an individual tracks the total gifts given by that person over his or her lifetime so that one knows how much of the unified credit has already been used up while he/she was living, and that is used in determining if there is a taxable estate or not at the person's death. To be basic, the current law says that a person can transfer $5.34 million of assets either by gift during his lifetime or at his death via his estate without paying tax. That is what the unified estate and gift tax exclusion is all about.
Does that help you at all?