The fair market value of assets other than stock, cash and interests in common trust funds is determined annually except as described in Assets Held for Less Than One Year. The valuation may be made by private foundation employees or by any other person, whether or not that person is a disqualified person. Such a valuation, if accepted by the IRS, is valid only for the tax year for which it is made. A new valuation is required for the following tax year. However, the fair market value of any interest in realty, including any improvements thereon, may be determined on a five-year basis by a written, certified, independent appraisal by a qualified person who is neither a disqualified person nor an employee of the private foundation. The appraisal must contain a statement to the effect that, in the appraiser's opinion, the appraised assets were valued in accordance with valuation principles regularly employed in making appraisals of such property using all reasonable valuation methods. The foundation must keep a copy of the independent appraisal for its records. If a valuation is reasonable, the foundation may use it for the tax year for which the valuation is made and for each of the four following tax years. Any valuation of real property by a certified, independent appraisal may be replaced during the five-year period by a later five-year valuation by a certified, independent appraisal or by an annual valuation. The most recent valuation will be used in figuring the foundation's minimum investment return. The valuation must be made no later than the last day of the first tax year for which the new valuation applies. A valuation, if properly made according to the rules discussed here, will not be disturbed by the IRS during the five-year period for which it applies, even if the actual fair market value of the property changes during that period. Commonly accepted valuation methods must be used in making the appraisal. A valuation based on acceptable methods of valuing property for federal estate tax purposes is acceptable. An appraisal is a determination of fair market value and should not be construed in a technical sense to be peculiar to particular property or interests therein as, for example, mineral interests in real property.